0
We're unable to sign you in at this time. Please try again in a few minutes.
Retry
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
Retry
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......
Article |

Recurrent Wheezing in the Third Year of Life Among Children Born at 32 Weeks' Gestation or Later:  Relationship to Laboratory-Confirmed, Medically Attended Infection With Respiratory Syncytial Virus During the First Year of Life FREE

Gabriel J. Escobar, MD; Arona Ragins, MA; Sherian Xu Li, MS; Laura Prager, MD; Anthony S. Masaquel, PhD, MPH; Patricia Kipnis, PhD
[+] Author Affiliations

Author Affiliations: Division of Research, Systems Research Initiative and Perinatal Research Unit, Kaiser Permanente Medical Care Program, Oakland, California (Drs Escobar and Kipnis and Mss Ragins and Li); Department of Pediatrics, Kaiser Permanente Medical Center, Walnut Creek, California (Dr Escobar and Mss Ragins and Li); Department of Pediatrics, Kaiser Permanente Medical Center, Daly City, California (Dr Prager); MedImmune LLC, Gaithersburg, Maryland (Dr Masaquel); and Department of Management Information and Analysis, Kaiser Foundation Health Plan Inc, Oakland, California (Dr Kipnis).


Arch Pediatr Adolesc Med. 2010;164(10):915-922. doi:10.1001/archpediatrics.2010.177.
Text Size: A A A
Published online

Objective  To quantify the relationship between recurrent wheezing (RW) in the third year of life and respiratory syncytial virus (RSV) infection, prematurity, and neonatal oxygen exposure.

Design  Retrospective cohort study linking inpatient, outpatient, and laboratory databases for cohort assembly and logistic regression analysis.

Setting  Integrated health care delivery system in Northern California.

Participants  A total of 71 102 children born from 1996 to 2002 at 32 weeks' gestational age or later who were health plan members for 9 or more months in their first and third years.

Main Exposures  Laboratory-confirmed, medically attended RSV infection during first year and supplemental oxygen during birth hospitalization.

Outcome Measures  Recurrent wheezing, quantified through outpatient visits, inpatient hospital stays, and asthma prescriptions.

Results  The rate of RW in the third year of life was 16.23% among premature infants with RSV and 6.22% among those without RSV. The risk of RW increased among infants who had an RSV outpatient encounter (adjusted odds ratio [AOR], 2.07; 95% CI, 1.61-2.67), uncomplicated RSV hospitalization (AOR, 4.66; 95% CI, 3.55-6.12), or prolonged RSV hospitalization (AOR, 3.42; 95% CI, 2.01-5.82) compared with infants without RSV encounters. Gestational age of 34 to 36 weeks was associated with increased risk of RW (AOR, 1.23; 95% CI 1.07-1.41) compared with 38 to 40 weeks, while a gestational age of 41 weeks or more was protective (AOR, 0.90; 95% CI, 0.81-0.99). Supplemental oxygen exposure was associated with increased risk at all levels.

Conclusion  Laboratory-confirmed, medically attended RSV infection, prematurity, and exposure to supplemental oxygen during the neonatal period have independent associations with the development of RW in the third year of life.

Figures in this Article

Respiratory syncytial virus (RSV) infection is a common event in childhood; rates approach 100% by 3 years of age,1 resulting in an innocuous upper respiratory infection in most infants. However, a significant number develop severe lower respiratory tract infections.24 Respiratory syncytial virus is responsible for 50% to 80% of bronchiolitis hospitalizations5 and is the leading cause of hospitalization in children younger than 1 year.6 Approximately 75 000 to 125 000 hospitalizations associated with RSV occur each year in the United States.2

The RSV hospitalization patterns are a good indicator of the burden of severe infection. The burden of less severe RSV infections (those only requiring outpatient care) is not trivial; it is estimated that 1 in 13 visits to a physician's office result from RSV disease.7 Moreover, RSV bronchiolitis during infancy is associated with subsequent development of recurrent wheezing and early childhood asthma.815 Infants at high risk of RSV disease, including the very premature, may face severe respiratory complications after RSV infection.16 Although moderate prematurity is associated with increased rates of RSV infection,17 few recent data are available on the effects of RSV infection or consequences in late-preterm infants.

This study examined the long-term effect of RSV bronchiolitis during infancy in moderately preterm and full-term infants. We hypothesized that laboratory-confirmed, medically attended RSV infection (henceforth referred to as RSV infection) during the first year of life would show a strong association with the risk of recurrent wheezing (RW) in the third year.

Our study setting was the Northern California Kaiser Permanente Medical Care Program (KPMCP). This study was approved by the Northern California KPMCP Institutional Review Board, which has jurisdiction over all of the hospitals and clinics involved in the study. The inception cohort consisted of infants who met the following criteria: birth at the KPMCP Oakland, Hayward, Sacramento, San Francisco, Santa Clara, or Walnut Creek, California, hospitals; date of birth from January 1, 1996, through December 31, 2002; 32 weeks' or later gestational age (GA) at birth; infant survival of birth hospitalization; and use or membership in Kaiser Foundation Health Plan Inc during the first year of life.

OUTCOMES

Our primary study outcome was the occurrence of RW in the third year of life (second birthday through the day before the third birthday). Before extracting electronic data, RW was defined as 3 or more outpatient encounters, at least 14 days apart, with a diagnosis of asthma (International Classification of Diseases18[ICD] code 493.xx) or wheezing (ICD code 786.07); and/or 1 or more asthma or wheezing encounter with a prescription for oral corticosteroids within 2 days before or 7 days after the encounter; and/or 1 or more hospitalizations with a diagnosis of asthma or wheezing with a total hospital length of stay of 24 hours or longer or until death occurred; and/or 4 or more dispensing events (prescriptions that were picked up), at least 14 days apart, on which selected asthma medications were prescribed in addition to 1 or more encounters with a diagnosis of asthma or wheezing; and/or death outside the hospital setting with the cause of death listed as asthma or wheezing. Selected asthma medications included rescue medications (including albuterol and theophylline), inhaled corticosteroids (including beclomethasone dipropionate, budesonide, and flunisolide), leukotriene inhibitors (montelukast), or oral corticosteroids (including dexamethasone and prednisone). The full list of 640 medications is available on request.

PREDICTORS

The primary study predictor was the occurrence of RSV infection in the first year of life. We also examined whether infants were infected with adenovirus, parainfluenza virus, influenza A or B virus, or Bordetella pertussis. We considered outpatient visits, emergency department visits, and inpatient hospitalization with diagnostic codes for each type of pathogen to be medically attended events. A medically attended event was considered to be laboratory confirmed if there was a positive result on a test for the pathogen within14 days before or after the encounter. During the period covered by this study, laboratory confirmation for these pathogens in the KPMCP was by direct fluorescent antibody testing or culture. We categorized medically attended encounters of RSV and other pathogens as outpatient (including scheduled clinic visits, unscheduled urgent care visits, and emergency department visits), uncomplicated hospitalizations (hospitalizations with a total length of stay of <96 hours without assisted ventilation), or prolonged hospitalizations (hospitalizations with a total length of stay of 96 hours or more, or in which assisted ventilation was required).

We also examined, for each infant, sex, race, maternal age, birth weight, GA, a discharge diagnosis of bronchopulmonary dysplasia (BPD) or congenital anomaly (ICD codes 425.3x, 425.4x, 425.8x, 745.xx, 746.xx, and 747.xx), discharge from birth hospitalization during the California RSV season (November through March), the number of siblings present in the home (≥1 sibling <5 years of age), and hospitalization for an unspecified respiratory illness (ICD codes 480.8, 480.9, 481.xx, 482.xx, 483.xx, 484.xx, 485.xx, and 486.xx) categorized as none, uncomplicated hospitalization, and prolonged hospitalization. For hospitalization records, we also determined the total length of stay, which included concatenating records in cases in which interhospital transport occurred, and whether the infant experienced assisted ventilation (ICD codes 93.90, 93.91, and 96.7x).

We combined electronic data elements to create 4 composite variables: small for gestational age (SGA), neonatal oxygen exposure, family history of asthma, and membership status. We classified infants as being SGA (<5th percentile) using birth weight and GA according to the algorithm developed by Brenner et al.19 We fitted a smooth cubic spline to predict the probability of RW as a function of total oxygen exposure separately for births occurring at 32 to 37 and 37 weeks' or greater GA. Both curves showed a flat effect for total oxygen exposure at less than 200 hours and a clear increase at more than 200 hours, suggesting a step function and no interaction between GA and total length of oxygen therapy. For infants treated in the neonatal intensive care unit, we created an oxygen exposure variable: no supplemental oxygen exposure during the neonatal period, no BPD; supplemental oxygen exposure of 1 to less than 200 hours during the neonatal period, no BPD; supplemental exposure 200 or more hours during the neonatal period, no BPD; and BPD. Infants who did not require intensive care as newborns were classified as having no supplemental oxygen exposure. Parental asthma history was established by scanning the parent's records for the period 18 months before to 6 months after the infant's birth and determining whether the parent had 2 or more clinical visits 14 days apart with an ICD code 493.xx for asthma and/or the parent's electronic record listed asthma on their significant problem list. The parents' significant problem list was scanned to determine whether either parent listed smoking as a problem during the infants' first year of life. We linked the children's use and membership data and created a monthly membership variable that was set equal to 1 (patient was a member during that month and/or had outpatient or inpatient use during that month) or 0 (patient was not a member during that month and did not have outpatient or inpatient use during that month) to determine eligibility for inclusion in the study cohort.

DATA COLLECTION

The KPMCP's information systems use a common medical record number for all inpatient, outpatient, and administrative encounters in all facilities, permitting extraction and linkage of patient data using methods that have been previously described.2023 Care received outside of the program was also tracked. We identified infants using the KPMCP hospitalization database and the Neonatal Minimum Data Set,24 a research database that captures supplemental oxygen use and assisted ventilation among infants receiving neonatal intensive care. These records were linked to patient demographic, membership, laboratory, pharmacy, outpatient encounter, and hospitalization databases to obtain the previously described variables. To ensure data quality, we audited any questionable laboratory test results, clinical encounters, or prescription patterns and manually corrected records when necessary. For comparison with the general US population, we randomly sampled patient records to estimate daycare use and passive smoke exposure in the first year of life. We chose 165 infants of 37 weeks' or less GA who did not have RSV infection in the first 6 months of life and 165 who did, as well as 55 infants of 38 or more weeks' GA with RSV infection and 55 without in the first 6 months of life, for a total of 440 infants. After manual medical record abstraction, sufficient data for analysis were available in 417 of the 440 records. Randomly selecting 1 infant per mother left 406 records (152/165 infants ≤37 weeks' GA with RSV; 152/165 infants ≤37 weeks' GA without RSV; 49/55 infants ≥38 weeks' GA with RSV; and 53/55 infants ≥38 weeks' GA without RSV). We estimated prevalence rates factoring the differential sampling fractions used.

STATISTICAL ANALYSIS

Statistical analyses were conducted using SAS (SAS Institute, Cary, North Carolina). Recurrent wheezing odds ratios (OR) for all predictors were calculated using logistic regression25 with RW in the third year of life as the outcome and each of the predictors as the only explanatory variable. Values of categorical variables were compared using χ2 or Fisher exact test. Normally distributed continuous variables were compared using the t test. Comparisons of nonnormally distributed continuous variables used the Wilcoxon rank sum test.

We conducted 4 multivariate analyses to estimate the effect of RSV infection and other predictors on RW. Our model predictors were selected before the study began and were based on biologic plausibility and previous reports on RSV infection. These analyses used logistic regression and Cox proportional hazards modeling25 (to account for censoring of infants who were Kaiser Foundation Health Plan Inc members for ≥9 months during their first year of life but who were members for <9 months during their third year) and 2 RSV exposure variables (RSV infection in the first 6 and 12 months of age).

The relative contribution of each predictor was calculated using the differences between the log likelihood of the full model and the log likelihood of a model without each of the predictors and was defined as the ratio of its log likelihood difference to the sum of the likelihood differences from all predictors times 100.26

To account for the clustering of multiple deliveries and multiple births by the same mother, we calculated robust standard errors for a mother effect using the robust sandwich variance estimates from Lin and Wei27 in the Cox regression. The results from this model were compared with those from a Cox regression model in which a single infant was selected from mothers with multiple deliveries during the study period and from mothers with multiple gestations. Because clustering had little effect on the final results, we present only the results from our logistic regression model involving our cohort with only 1 observation per mother and only 1 infant per mother.

To address underdiagnosis of RSV, we conducted an analysis in which we simulated what might have occurred had all infants been tested. In this analysis, we simulated the effects that universal testing might have had on our findings, assuming the same proportion of positive results among those not tested and also by varying the positivity rate by +10% and −10%. The results of this simulation can be found in eAppendix 2(http://www.archpediatrics.com).

Scanning of KPMCP databases identified 126 837 infants who survived birth hospitalization to discharge from 1996 through 2002 (Figure 1). We excluded 277 infants whose records had missing data and 1803 infants younger than 32 weeks' GA, leaving a total of 124 777 infants. To avoid statistical nonindependence owing to multiple deliveries per mother and multiple births per delivery, we identified all maternal records in which a woman gave birth to more than 1 infant during the study period and randomly selected a single delivery to be retained in our study cohort, excluding 19 472 infants. From all remaining deliveries with a multiple gestation, 1 infant was randomly selected to be retained in our study cohort, thereby excluding 1731 infants, leaving a cohort of 103 574 infants of 32 weeks' or greater GA. An additional 32 472 infants were excluded for not meeting membership criteria, leaving the final study cohort that consisted of 71 102 infants of 32 weeks' or greater GA.

Place holder to copy figure label and caption
Figure 1.

Flowchart of study cohorts identified from Kaiser Permanente Medical Care Program databases from 1996 to 2002. For multiple births, 1 infant was randomly selected and retained for inclusion in the cohort. GA indicates gestational age; RSV, respiratory syncytial virus; and RW, recurrent wheezing.

Graphic Jump Location

Table 1 summarizes the characteristics of the study cohort and shows that it is ethnically diverse, with a slight preponderance of boys (51%). Most mothers (73.8%) were aged 18 to 34 years. From the mothers' records, 3.7% of infants had a family history of asthma.

Table Graphic Jump LocationTable 1. Characteristics of Infants Born 1996 Through 2002 by Gestational Age Categories

Table 2 provides key bivariate comparisons between infants with and without RW and unadjusted odds of RW. Laboratory-confirmed, medically attended infection with RSV, prematurity, and oxygen exposure during the neonatal period were associated with increased risk of RW. Other predictors significantly associated with increased risk were male sex, SGA, African American or Asian race, family history of asthma, congenital anomaly, infection with other pathogens described previously, or hospitalization with an unspecified respiratory illness. Only 1 predictor (≥41 weeks' GA) was associated with significantly decreased risk (unadjusted OR, 0.88; 95% confidence interval [CI], 0.80-0.98). In other analyses (not shown), the season of hospital discharge was not associated with RW; therefore, it was not included in our final multivariate models. The rate of RW among premature infants in our cohort (32-36 weeks' GA) with an RSV infection was 16.23%; the rate among those who did not have RSV infection was 6.22% (unadjusted OR, 2.92; 95% CI, 1.88-4.55); and the proportions among infants of 37 weeks' or greater GA with and without RSV infection were 12.56% and 4.36%, respectively (unadjusted OR, 3.15; 95% CI, 2.61-3.80). The rate of RW among all infants with unspecified respiration-related hospitalization was 16.31%.

Table Graphic Jump LocationTable 2. Bivariate Comparisons of Infants With and Without Recurrent Wheezing and Unadjusted Odds of Recurrent Wheezing

We performed 4 multivariate analyses based on the period for the exposure of interest (medically attended RSV infection in the first 6 or 12 months of life) and the methodology used (logistic or Cox proportional hazards regression). Because of the similarity of the results of these analyses, only the results of our logistic regression analyses that used the 12-month exposure period are presented here; the other 3 analyses are presented in eAppendix 1.

In our multivariate analyses, after controlling for the other predictors in the model, SGA status, maternal age, presence of siblings younger than 5 years in the household, and having a congenital anomaly were not significantly associated with RW (Table 3 and Table 4; Figure 2 and Figure 3). A GA of 41 weeks or greater was protective (adjusted OR [AOR], 0.90; 95% CI, 0.81-0.99). Other predictors with a statistically significant association with RW included RSV infection, decreasing gestation, any neonatal oxygen exposure, male sex, African American or Asian race, family history of asthma, and hospitalization for an unspecified respiratory illness. Infection with the other listed pathogens was not a consistent predictor for RW after controlling for covariates.

Place holder to copy figure label and caption
Figure 2.

Adjusted odds ratios (OR) and 95% confidence intervals for respiratory syncytial virus (RSV) exposure during the first year of life . Adjusted ORs and 95% confidence intervals were calculated for each individual week of gestational age (using 40 weeks as the reference), controlling for all other factors. Note that RSV infection that only involved an outpatient visit has a significantly elevated adjusted OR compared with no infection but that this is lower than the adjusted ORs for RSV infection in which hospitalization occurred. * P < .001. The number (percent) of patients with recurrent wheezing that involved no visit was 3144 (4.5); outpatient visit, 69 (9.6); uncomplicated hospitalization, 68 (19.3); and prolonged hospitalization, 17 (15.9).

Graphic Jump Location
Place holder to copy figure label and caption
Figure 3.

Effects of gestational age (GA) on the risk of developing recurrent wheezing in the third year of life. Adjusted odds ratios (OR) and 95% confidence intervals were calculated for each individual week of GA (using 40 weeks' GA as the reference), controlling for all other factors. To generate these figures, 40 weeks' GA was set as the reference, and the adjusted ORs are for each gestational week, controlling for all other predictors described in the text. The number (percent) of infants with recurrent wheezing at weeks 32 through 41+ were 37 (9.7), 33 (6.8), 54 (6.6), 80 (6.3), 132 (6.0), 244 (5.6), 494 (4.9), 872 (4.7), 893 (4.2), and 459 (4.0), respectively.

Graphic Jump Location
Table Graphic Jump LocationTable 3. Risk Factors for Recurrent Wheezing in Third Year Using Logistic Regression Model Adjusting for Infant and Mother Demographic and Clinical Characteristicsa
Table Graphic Jump LocationTable 4. Relative Contributiona of Predictors to Multivariate Model's Explanatory Power

Infants with RSV infection involving uncomplicated (AOR, 4.66; 95% CI, 1.61-2.67) and prolonged hospitalization (AOR, 3.42; 95% CI, 2.01-5.82) were at greater risk for RW than those with RSV infection involving an outpatient encounter (AOR, 2.07; 95% CI, 1.61-2.67) compared with infants without any visit for RSV (Figure 2). The proportion of infants with RW increased with decreasing GA at birth, beginning at 37 weeks' GA (Figure 3).

Although many predictors reached statistical significance, the overall discrimination and explanatory power of our model were low. The area under the receiver operator characteristic curve for the model was 0.62, with a Hosmer-Lemeshow P value of .88. In terms of explanatory power, the 3 predictors that contributed the most to the total model χ2 were infant sex (33%), family history of asthma (23%), and RSV infection (20%) (Table 4).

Based on our medical record review of randomly selected charts, daycare use during the first year of life was 6.4% (95% CI, 1.1-11.8%), while the prevalence of smokers in the home during the first year of life was 5.0% (95% CI, 0.0-10.3%). Review of parents' electronic records showed that 1 or more parents smoked in 3.2% of the study families during the 6 months preceding the birth of the study infant, and in 3.1% of families during the first and second 6 months of life.

In this retrospective cohort study, we found that 3 important risk factors—RSV infection, moderate prematurity, and exposure to supplemental oxygen in the neonatal period—have a statistically significant association with the development of RW in the third year of life. The effect of decreasing GA becomes apparent at 37 weeks' GA, while 41 weeks' or more GA was protective. This study supports the growing body of literature indicating that increased morbidity is associated with moderate prematurity. In addition, male sex, family history of asthma, African American or Asian race, and unspecified respiratory hospitalization were associated with an increased risk of RW. Several variables that were considered to be associated with increased risk of RW (siblings aged <5 years of age in the home, SGA status, and congenital anomalies) were not statistically significant after controlling for the other variables in our model.

Henderson et al13 found that approximately 28.1% of infants with RSV lower respiratory tract infection during the first few months of life developed RW by 30 to 42 months of age. Similarly, 30% and 43% of young infants with RSV had asthma by 7 and 13 years of age, respectively, in studies by Sigur et al.8,12 A more recent study by Wu et al28 demonstrated a causal association of infant age at the peak of winter virus season and the development of early childhood asthma, providing theoretical insight on RSV as an important, modifiable, environmental risk factor and highlighting the importance of preventing RSV disease.

The effect of RSV severity on asthma during early childhood has been an area of special interest. From this perspective, our study findings should be considered in light of a recent population-based retrospective study of healthy full-term infants from the Tennessee Medicaid program by Carroll et al,29 which identified an association between bronchiolitis in early infancy and asthma by 5.5 years of age. Compared with infants with no bronchiolitis visit, infants with outpatient, emergency department, and hospital bronchiolitis visits had AORs of 1.86, 2.41, and 2.82, respectively, for the development of early childhood asthma. The study, however, was limited by its focus on healthy, full-term infants, excluding preterm infants. It also did not include laboratory-confirmed cases of RSV infection, nor did it address the possible effects of other viruses (eg, adenovirus). Our findings clearly complement and expand on these results by examining the contribution of medically attended, unspecified respiratory hospitalizations to the risk of RW. Many of these hospitalizations may be because of RSV infection, and the results were consistent with our observations for laboratory-confirmed, medically-attended RSV infection. Because our databases included GA in weeks, they also permitted expanding on the findings of Boyce et al,17 one of the few large studies on RSV that included late preterm infants.

To our knowledge, this is the first study to document an association between oxygen exposure in infants of 32 weeks' or greater GA and development of RW in early childhood. While the dangers of oxygen exposure among very premature infants have been known for years, the importance of oxygen toxicity in more mature newborns is only starting to be appreciated. For example, Spector et al30 documented an association between neonatal oxygen exposure and cancer, and Vento et al31,32 found that room air resuscitation may be safer for asphyxiated newborns than that using 100% oxygen. Concern about such toxicity has led the American Academy of Pediatrics to endorse new guidelines that permit using room air for resuscitation of newborns instead of 100% oxygen,33 part of a more widespread reappraisal of the potential toxicity of oxygen.34 Given the observational nature of our study, we cannot exclude that the association with oxygen exposure is the result of confounding by severity of illness (ie, RW could be due to another mediating factor that manifests with some form of respiratory difficulty requiring oxygen in the neonatal period).

Although intriguing, the other associations we found do not constitute causality, and some are difficult to distinguish from possible confounding factors, as we note with respect to oxygen exposure. Importantly, almost two-thirds of our model's explanatory power came from 3 factors that may have a strong genetic and/or epigenetic component: sex, family history of asthma, and race. This suggests that another factor—which this study could not address—may be playing an important role: infants whose response to RSV infection is severe enough to come to medical attention may represent a population genetically predetermined to be hypersensitive to developing bronchoconstriction when confronted with a trigger.

The major limitation of our study is that not all infants were tested for RSV (for example, among hospitalized infants with respiratory illnesses, 43% were not tested). Given the absence of systematic testing for respiratory pathogens, we cannot exclude the possibility of underdiagnosis in this retrospective study. While we suspect that lack of such testing leads to underestimation of the effect of RSV, we cannot exclude the presence of other causal factors including genetic ones and ones mediated by other respiratory illnesses such as Rhinovirus infection. More research will be needed to understand the role of RSV, a potentially modifiable risk factor, in the causal pathway for RW.

Although our model's discrimination was relatively low, it considers many factors that are known predictors of asthma or that may confound the RSV effect. All of these predictors had statistically significant AORs, and because the model parameters are not routinely reported by other investigators, it is difficult to compare our results with previous studies.

Our study was conducted in a unique health care setting, which may limit generalizing our study's findings to other populations. For example, in our population, only 6.4% of the infants younger than 1 year were in some form of organized daycare, less than the 15% rate reported by the most recent US Census Bureau report.35(pp70-86) Moreover, Northern California KPMCP is unusual in having a special program (Early Start) that targets perinatal substance abuse, including smoking.3638 Our estimate of the prevalence of tobacco exposure during the first year of life (3.1%) is much lower than reported elsewhere in the country, where rates of smoking soon after pregnancy range between 7.3% and 39.3%39,40 but is consistent with recent internal surveys conducted by the Early Start program that reported a smoking rate of 4.2% among pregnant women in the KPMCP in 2008 (M. A. Armstrong, written communication, August 2009).

This retrospective study suggests that GA is an important risk factor for developing RW. Premature infants have a greater risk of developing RW than full-term infants after RSV infection. Furthermore, infants with more severe RSV infections, particularly those who require hospitalization, had a higher risk of developing RW in early childhood compared with infants with less severe infection. Similarly, neonatal use of supplemental oxygen was associated with increased risk of RW. Several genetic and environmental factors in our study (including race, smoking in the home, and daycare attendance) were associated with an increased risk of RW and may provide promising areas for more detailed research that should include follow-up extending beyond the third year of life.

Correspondence: Gabriel J. Escobar, MD, Division of Research, Systems Research Initiative and Perinatal Research Unit, Kaiser Permanente Medical Care Program, 2000 Broadway, 2nd Floor, Oakland, CA 94612 (gabriel.escobar@kp.org).

Accepted for Publication: March 10, 2010.

Author Contributions: Dr Escobar was the principal investigator and had full access to all of the data in the study and supervised data collection, data cleaning, and, in conjunction with Dr Kipnis, the project statistician, supervised all project analyses. Study concept and design: Escobar. Acquisition of data: Escobar, Ragins, and Li. Analysis and interpretation of data: Escobar, Li, Prager, Masaquel, and Kipnis. Drafting of the manuscript: Escobar, Ragins, Masaquel, and Kipnis. Critical revision of the manuscript for important intellectual content: Li, Prager, and Kipnis. Statistical analysis: Escobar, Masaquel, and Kipnis. Obtained funding: Escobar. Administrative, technical, and material support: Escobar, Ragins, Li, and Prager. Study supervision: Escobar, Ragins, and Kipnis.

Financial Disclosure: Dr Masaquel is an employee of MedImmune LLC and receives an incentive plan.

Funding/Support: This study was supported by a contract with MedImmune LLC.

Role of the Sponsor: MedImmune LLC was involved in the design of the study, interpretation of the data, and review of the manuscript. All authors agreed on the final text and conclusions of the manuscript, which was also reviewed by Joseph V. Selby, MD, MPH, Director of the Kaiser Permanente Division of Research, and Parthiv J. Mahadevia, MD, MPH, Senior Director, Health Outcomes and Pharmacoeconomics, MedImmune LLC.

Previous Presentations: Portions of this study were presented at the Hot Topics in Neonatology Conference; December 9, 2008; Washington, DC; the Society for Pediatric Research meetings; May 5, 2009; Baltimore, Maryland; the Kaiser Permanente Pediatrics Conference; July 15, 2009; Kauai, Hawaii; and the Pediatric Academic Society Annual Meeting; May 1-4, 2010; Vancouver, Canada.

Additional Contributions: We also wish to thank Jennifer Graff, PharmD, for assistance during the initial phases of the study, and Dennis Andaya, RHIT, for performing medical record review. We acknowledge Gerard P. Johnson, PhD, John E. Fincke, PhD, and Susan E. DeRocco, PhD, from Complete Healthcare Communications Inc for editorial support of the manuscript.

Glezen  WPTaber  LHFrank  ALKasel  JA Risk of primary infection and reinfection with respiratory syncytial virus. Am J Dis Child 1986;140 (6) 543- 546
PubMed
Shay  DKHolman  RCNewman  RDLiu  LLStout  JWAnderson  LJ Bronchiolitis-associated hospitalizations among US children, 1980-1996. JAMA 1999;282 (15) 1440- 1446
PubMed
Sampalis  JS Morbidity and mortality after RSV-associated hospitalizations among premature Canadian infants. J Pediatr 2003;143 (5) ((suppl)) S150- S156
PubMed
Broughton  SRoberts  AFox  G  et al.  Prospective study of healthcare utilisation and respiratory morbidity due to RSV infection in prematurely born infants. Thorax 2005;60 (12) 1039- 1044
PubMed
Hall  CB Respiratory syncytial virus and parainfluenza virus. N Engl J Med 2001;344 (25) 1917- 1928
PubMed
Leader  SKohlhase  K Respiratory syncytial virus-coded pediatric hospitalizations, 1997 to 1999. Pediatr Infect Dis J 2002;21 (7) 629- 632
PubMed
Hall  CBWeinberg  GAIwane  MK  et al.  The burden of respiratory syncytial virus infection in young children. N Engl J Med 2009;360 (6) 588- 598
PubMed
Sigurs  NBjarnason  RSigurbergsson  FKjellman  BBjörkstén  B Asthma and immunoglobulin E antibodies after respiratory syncytial virus bronchiolitis: a prospective cohort study with matched controls. Pediatrics 1995;95 (4) 500- 505
PubMed
Stein  RTSherrill  DMorgan  WJ  et al.  Respiratory syncytial virus in early life and risk of wheeze and allergy by age 13 years. Lancet 1999;354 (9178) 541- 545
PubMed
Bont  LAalderen  WMKimpen  JL Long-term consequences of respiratory syncytial virus (RSV) bronchiolitis. Paediatr Respir Rev 2000;1 (3) 221- 227
PubMed
Martinez  FD Respiratory syncytial virus bronchiolitis and the pathogenesis of childhood asthma. Pediatr Infect Dis J 2003;22 (2) ((suppl)) S76- S82
PubMed
Sigurs  NGustafsson  PMBjarnason  R  et al.  Severe respiratory syncytial virus bronchiolitis in infancy and asthma and allergy at age 13. Am J Respir Crit Care Med 2005;171 (2) 137- 141
PubMed
Henderson  JHilliard  TNSherriff  AStalker  DAl Shammari  NThomas  HM Hospitalization for RSV bronchiolitis before 12 months of age and subsequent asthma, atopy and wheeze: a longitudinal birth cohort study. Pediatr Allergy Immunol 2005;16 (5) 386- 392
PubMed
Carroll  KNHartert  TV The impact of respiratory viral infection on wheezing illnesses and asthma exacerbations. Immunol Allergy Clin North Am 2008;28 (3) 539- 561, viii
PubMed
Mohapatra  SSBoyapalle  S Epidemiologic, experimental, and clinical links between respiratory syncytial virus infection and asthma. Clin Microbiol Rev 2008;21 (3) 495- 504
PubMed
Friedrich  LPitrez  PMStein  RTGoldani  MTepper  RJones  MH Growth rate of lung function in healthy preterm infants. Am J Respir Crit Care Med 2007;176 (12) 1269- 1273
PubMed
Boyce  TGMellen  BGMitchel  EF  JrWright  PFGriffin  MR Rates of hospitalization for respiratory syncytial virus infection among children in medicaid. J Pediatr 2000;137 (6) 865- 870
PubMed
Practice Management Information Corporation, International Classification of Diseases, Ninth Revision (ICD-9) Vol 1, 2, and 3: Clinical Modification.  Los Angeles, CA PMIC2006;
Brenner  WEEdelman  DAHendricks  CH A standard of fetal growth for the United States of America. Am J Obstet Gynecol 1976;126 (5) 555- 564
PubMed
Selby  JV Linking automated databases for research in managed care settings. Ann Intern Med 1997;127 (8 pt 2) 719- 724
PubMed
Joffe  SEscobar  GJBlack  SBArmstrong  MALieu  TA Rehospitalization for respiratory syncytial virus among premature infants. Pediatrics 1999;104 (4 pt 1) 894- 899
PubMed
Go  ASHylek  EMChang  Y  et al.  Anticoagulation therapy for stroke prevention in atrial fibrillation: how well do randomized trials translate into clinical practice? JAMA 2003;290 (20) 2685- 2692
PubMed
Escobar  GJClark  RHGreene  JD Short-term outcomes of infants born at 35 and 36 weeks gestation: we need to ask more questions. Semin Perinatol 2006;30 (1) 28- 33
PubMed
Escobar  GJFischer  AKremers  RUsatin  MSMacedo  AMGardner  MN Rapid retrieval of neonatal outcomes data: the Kaiser Permanente Neonatal Minimum Data Set. Qual Manag Health Care 1997;5 (4) 19- 33
PubMed
Harrell  F Regression Modeling Strategies with Applications to Linear Models, Logistic Regression, and Survival Analysis.  New York, NY Springer Verlag2001;
Render  MLKim  HMWelsh  DE  et al. VA ICU Project (VIP) Investigators, Automated intensive care unit risk adjustment: results from a National Veterans Affairs study. Crit Care Med 2003;31 (6) 1638- 1646
PubMed
Lin  DWei  LJ The robust inference for the Cox proportional hazards model. J Am Stat Assoc 1989;84 (408) 1074- 107810.2307/2290085
Wu  PDupont  WDGriffin  MR  et al.  Evidence of a causal role of winter virus infection during infancy in early childhood asthma. Am J Respir Crit Care Med 2008;178 (11) 1123- 1129
PubMed
Carroll  KNWu  PGebretsadik  T  et al.  The severity-dependent relationship of infant bronchiolitis on the risk and morbidity of early childhood asthma. J Allergy Clin Immunol 2009;123 (5) 1055- 1061, 1061, e1
PubMed
Spector  LGKlebanoff  MAFeusner  JHGeorgieff  MKRoss  JA Childhood cancer following neonatal oxygen supplementation. J Pediatr 2005;147 (1) 27- 31
PubMed
Martin  RJWalsh  MCCarlo  WA Reevaluating neonatal resuscitation with 100% oxygen. Am J Respir Crit Care Med 2005;172 (11) 1360- 1361
PubMed
Vento  MSastre  JAsensi  MAViña  J Room-air resuscitation causes less damage to heart and kidney than 100% oxygen. Am J Respir Crit Care Med 2005;172 (11) 1393- 1398
PubMed
American Academy of Pediatrics, Update on oxygen versus room air: Neonatal Resuscitation Program Instructor update. Am Acad Pediatr 2007;16 (2) 2
Tin  WHey  E The medical use of oxygen: a century of research in animals and humans. NeoReviews 2003;12e349- e35510.1542/neo.4-12-e349
Smith  K Who's Minding the Kids? Child Care Arrangements: Spring 1997.  Washington, DC US Census Bureau2002;
Armstrong  MALieberman  LCarpenter  DM  et al.  Early Start: an obstetric clinic-based, perinatal substance abuse intervention program. Qual Manag Health Care 2001;9 (2) 6- 15
PubMed
Armstrong  MAGonzales Osejo  VLieberman  LCarpenter  DMPantoja  PMEscobar  GJ Perinatal substance abuse intervention in obstetric clinics decreases adverse neonatal outcomes. J Perinatol 2003;23 (1) 3- 9
PubMed
Goler  NCArmstrong  MATaillac  CJOsejo  VM Substance abuse treatment linked with prenatal visits improves perinatal outcomes: a new standard. J Perinatol 2008;28 (9) 597- 603
PubMed
Tong  VTJones  JRDietz  PMD’Angelo  DBombard  JMCenters for Disease Control and Prevention (CDC), Trends in smoking before, during, and after pregnancy: Pregnancy Risk Assessment Monitoring System (PRAMS), United States, 31 sites, 2000-2005. MMWR Surveill Summ 2009;58 (4) 1- 29
PubMed
Martin  JAHamilton  BESutton  PDVentura  SJMenacker  FKirmeyer  S Births: final data for 2004. Natl Vital Stat Rep 2006;55 (1) 1- 101
PubMed

Figures

Place holder to copy figure label and caption
Figure 1.

Flowchart of study cohorts identified from Kaiser Permanente Medical Care Program databases from 1996 to 2002. For multiple births, 1 infant was randomly selected and retained for inclusion in the cohort. GA indicates gestational age; RSV, respiratory syncytial virus; and RW, recurrent wheezing.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.

Adjusted odds ratios (OR) and 95% confidence intervals for respiratory syncytial virus (RSV) exposure during the first year of life . Adjusted ORs and 95% confidence intervals were calculated for each individual week of gestational age (using 40 weeks as the reference), controlling for all other factors. Note that RSV infection that only involved an outpatient visit has a significantly elevated adjusted OR compared with no infection but that this is lower than the adjusted ORs for RSV infection in which hospitalization occurred. * P < .001. The number (percent) of patients with recurrent wheezing that involved no visit was 3144 (4.5); outpatient visit, 69 (9.6); uncomplicated hospitalization, 68 (19.3); and prolonged hospitalization, 17 (15.9).

Graphic Jump Location
Place holder to copy figure label and caption
Figure 3.

Effects of gestational age (GA) on the risk of developing recurrent wheezing in the third year of life. Adjusted odds ratios (OR) and 95% confidence intervals were calculated for each individual week of GA (using 40 weeks' GA as the reference), controlling for all other factors. To generate these figures, 40 weeks' GA was set as the reference, and the adjusted ORs are for each gestational week, controlling for all other predictors described in the text. The number (percent) of infants with recurrent wheezing at weeks 32 through 41+ were 37 (9.7), 33 (6.8), 54 (6.6), 80 (6.3), 132 (6.0), 244 (5.6), 494 (4.9), 872 (4.7), 893 (4.2), and 459 (4.0), respectively.

Graphic Jump Location

Tables

Table Graphic Jump LocationTable 1. Characteristics of Infants Born 1996 Through 2002 by Gestational Age Categories
Table Graphic Jump LocationTable 2. Bivariate Comparisons of Infants With and Without Recurrent Wheezing and Unadjusted Odds of Recurrent Wheezing
Table Graphic Jump LocationTable 3. Risk Factors for Recurrent Wheezing in Third Year Using Logistic Regression Model Adjusting for Infant and Mother Demographic and Clinical Characteristicsa
Table Graphic Jump LocationTable 4. Relative Contributiona of Predictors to Multivariate Model's Explanatory Power

References

Glezen  WPTaber  LHFrank  ALKasel  JA Risk of primary infection and reinfection with respiratory syncytial virus. Am J Dis Child 1986;140 (6) 543- 546
PubMed
Shay  DKHolman  RCNewman  RDLiu  LLStout  JWAnderson  LJ Bronchiolitis-associated hospitalizations among US children, 1980-1996. JAMA 1999;282 (15) 1440- 1446
PubMed
Sampalis  JS Morbidity and mortality after RSV-associated hospitalizations among premature Canadian infants. J Pediatr 2003;143 (5) ((suppl)) S150- S156
PubMed
Broughton  SRoberts  AFox  G  et al.  Prospective study of healthcare utilisation and respiratory morbidity due to RSV infection in prematurely born infants. Thorax 2005;60 (12) 1039- 1044
PubMed
Hall  CB Respiratory syncytial virus and parainfluenza virus. N Engl J Med 2001;344 (25) 1917- 1928
PubMed
Leader  SKohlhase  K Respiratory syncytial virus-coded pediatric hospitalizations, 1997 to 1999. Pediatr Infect Dis J 2002;21 (7) 629- 632
PubMed
Hall  CBWeinberg  GAIwane  MK  et al.  The burden of respiratory syncytial virus infection in young children. N Engl J Med 2009;360 (6) 588- 598
PubMed
Sigurs  NBjarnason  RSigurbergsson  FKjellman  BBjörkstén  B Asthma and immunoglobulin E antibodies after respiratory syncytial virus bronchiolitis: a prospective cohort study with matched controls. Pediatrics 1995;95 (4) 500- 505
PubMed
Stein  RTSherrill  DMorgan  WJ  et al.  Respiratory syncytial virus in early life and risk of wheeze and allergy by age 13 years. Lancet 1999;354 (9178) 541- 545
PubMed
Bont  LAalderen  WMKimpen  JL Long-term consequences of respiratory syncytial virus (RSV) bronchiolitis. Paediatr Respir Rev 2000;1 (3) 221- 227
PubMed
Martinez  FD Respiratory syncytial virus bronchiolitis and the pathogenesis of childhood asthma. Pediatr Infect Dis J 2003;22 (2) ((suppl)) S76- S82
PubMed
Sigurs  NGustafsson  PMBjarnason  R  et al.  Severe respiratory syncytial virus bronchiolitis in infancy and asthma and allergy at age 13. Am J Respir Crit Care Med 2005;171 (2) 137- 141
PubMed
Henderson  JHilliard  TNSherriff  AStalker  DAl Shammari  NThomas  HM Hospitalization for RSV bronchiolitis before 12 months of age and subsequent asthma, atopy and wheeze: a longitudinal birth cohort study. Pediatr Allergy Immunol 2005;16 (5) 386- 392
PubMed
Carroll  KNHartert  TV The impact of respiratory viral infection on wheezing illnesses and asthma exacerbations. Immunol Allergy Clin North Am 2008;28 (3) 539- 561, viii
PubMed
Mohapatra  SSBoyapalle  S Epidemiologic, experimental, and clinical links between respiratory syncytial virus infection and asthma. Clin Microbiol Rev 2008;21 (3) 495- 504
PubMed
Friedrich  LPitrez  PMStein  RTGoldani  MTepper  RJones  MH Growth rate of lung function in healthy preterm infants. Am J Respir Crit Care Med 2007;176 (12) 1269- 1273
PubMed
Boyce  TGMellen  BGMitchel  EF  JrWright  PFGriffin  MR Rates of hospitalization for respiratory syncytial virus infection among children in medicaid. J Pediatr 2000;137 (6) 865- 870
PubMed
Practice Management Information Corporation, International Classification of Diseases, Ninth Revision (ICD-9) Vol 1, 2, and 3: Clinical Modification.  Los Angeles, CA PMIC2006;
Brenner  WEEdelman  DAHendricks  CH A standard of fetal growth for the United States of America. Am J Obstet Gynecol 1976;126 (5) 555- 564
PubMed
Selby  JV Linking automated databases for research in managed care settings. Ann Intern Med 1997;127 (8 pt 2) 719- 724
PubMed
Joffe  SEscobar  GJBlack  SBArmstrong  MALieu  TA Rehospitalization for respiratory syncytial virus among premature infants. Pediatrics 1999;104 (4 pt 1) 894- 899
PubMed
Go  ASHylek  EMChang  Y  et al.  Anticoagulation therapy for stroke prevention in atrial fibrillation: how well do randomized trials translate into clinical practice? JAMA 2003;290 (20) 2685- 2692
PubMed
Escobar  GJClark  RHGreene  JD Short-term outcomes of infants born at 35 and 36 weeks gestation: we need to ask more questions. Semin Perinatol 2006;30 (1) 28- 33
PubMed
Escobar  GJFischer  AKremers  RUsatin  MSMacedo  AMGardner  MN Rapid retrieval of neonatal outcomes data: the Kaiser Permanente Neonatal Minimum Data Set. Qual Manag Health Care 1997;5 (4) 19- 33
PubMed
Harrell  F Regression Modeling Strategies with Applications to Linear Models, Logistic Regression, and Survival Analysis.  New York, NY Springer Verlag2001;
Render  MLKim  HMWelsh  DE  et al. VA ICU Project (VIP) Investigators, Automated intensive care unit risk adjustment: results from a National Veterans Affairs study. Crit Care Med 2003;31 (6) 1638- 1646
PubMed
Lin  DWei  LJ The robust inference for the Cox proportional hazards model. J Am Stat Assoc 1989;84 (408) 1074- 107810.2307/2290085
Wu  PDupont  WDGriffin  MR  et al.  Evidence of a causal role of winter virus infection during infancy in early childhood asthma. Am J Respir Crit Care Med 2008;178 (11) 1123- 1129
PubMed
Carroll  KNWu  PGebretsadik  T  et al.  The severity-dependent relationship of infant bronchiolitis on the risk and morbidity of early childhood asthma. J Allergy Clin Immunol 2009;123 (5) 1055- 1061, 1061, e1
PubMed
Spector  LGKlebanoff  MAFeusner  JHGeorgieff  MKRoss  JA Childhood cancer following neonatal oxygen supplementation. J Pediatr 2005;147 (1) 27- 31
PubMed
Martin  RJWalsh  MCCarlo  WA Reevaluating neonatal resuscitation with 100% oxygen. Am J Respir Crit Care Med 2005;172 (11) 1360- 1361
PubMed
Vento  MSastre  JAsensi  MAViña  J Room-air resuscitation causes less damage to heart and kidney than 100% oxygen. Am J Respir Crit Care Med 2005;172 (11) 1393- 1398
PubMed
American Academy of Pediatrics, Update on oxygen versus room air: Neonatal Resuscitation Program Instructor update. Am Acad Pediatr 2007;16 (2) 2
Tin  WHey  E The medical use of oxygen: a century of research in animals and humans. NeoReviews 2003;12e349- e35510.1542/neo.4-12-e349
Smith  K Who's Minding the Kids? Child Care Arrangements: Spring 1997.  Washington, DC US Census Bureau2002;
Armstrong  MALieberman  LCarpenter  DM  et al.  Early Start: an obstetric clinic-based, perinatal substance abuse intervention program. Qual Manag Health Care 2001;9 (2) 6- 15
PubMed
Armstrong  MAGonzales Osejo  VLieberman  LCarpenter  DMPantoja  PMEscobar  GJ Perinatal substance abuse intervention in obstetric clinics decreases adverse neonatal outcomes. J Perinatol 2003;23 (1) 3- 9
PubMed
Goler  NCArmstrong  MATaillac  CJOsejo  VM Substance abuse treatment linked with prenatal visits improves perinatal outcomes: a new standard. J Perinatol 2008;28 (9) 597- 603
PubMed
Tong  VTJones  JRDietz  PMD’Angelo  DBombard  JMCenters for Disease Control and Prevention (CDC), Trends in smoking before, during, and after pregnancy: Pregnancy Risk Assessment Monitoring System (PRAMS), United States, 31 sites, 2000-2005. MMWR Surveill Summ 2009;58 (4) 1- 29
PubMed
Martin  JAHamilton  BESutton  PDVentura  SJMenacker  FKirmeyer  S Births: final data for 2004. Natl Vital Stat Rep 2006;55 (1) 1- 101
PubMed

Correspondence

CME
Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.
Submit a Comment

Multimedia

Recurrent Wheezing in the Third Year of Life Among Children Born at 32 Weeks' Gestation or Later: Relationship to Laboratory-Confirmed, Medically Attended Infection With Respiratory Syncytial Virus During the First Year of Life
Arch Pediatr Adolesc Med.2010;164(10):915-922.eAppendix

eAppendix -Download PDF (97 KB). This file requires Adobe Reader®.

eAppendix 1.

eAppendix 2.
Supplemental Content

Some tools below are only available to our subscribers or users with an online account.

Web of Science® Times Cited: 21

Related Content

Customize your page view by dragging & repositioning the boxes below.

Articles Related By Topic
Related Collections
PubMed Articles
JAMAevidence.com

The Rational Clinical Examination
Make the Diagnosis: Early Pregnancy

The Rational Clinical Examination
Original Article: Is This Patient Pregnant?