RT Journal A1 Coleman-Phox K, Li D T1 SHould we really encourage fan use?—reply JF Archives of Pediatrics & Adolescent Medicine JO Archives of Pediatrics & Adolescent Medicine YR 2009 FD May 4 VO 163 IS 5 SP 490 OP 491 DO 10.1001/archpediatrics.2009.80 UL http://dx.doi.org/10.1001/archpediatrics.2009.80 AB We appreciate Dr Vanderford and Dr Olsson's interest in our recent article on fan use and the risk of SIDS.1 We agree that bias is a threat to validity in any epidemiological study and must be rigorously assessed when interpreting findings. Our article addressed both selection bias and recall bias specifically, the same concerns Vanderford and Olsson raise in their letter. We addressed extensively, both in the current article and a previous one,2 possible self-selection bias due to a low participation rate. With the available data from birth certificates, the comparison between participating cases and controls and all eligible cases and controls did not provide support for the argument of strong selection bias, though the birth certificate did not include information on fan use.2