• Asthma epidemiology
• paediatric asthma

In the April 2009 issue of Thorax, Sherriff and co-authors report on data taken from the ALSPAC study, addressing the association between television viewing in early childhood and the development of asthma.1 They found that, after adjustment for body mass index, there was a relationship between the two, showing a significant trend.

I was surprised to see that television viewing was viewed solely as a proxy for a sedentary lifestyle, but not as being associated with other risk factors for developing asthma. For example, although the authors corrected for smoking during pregnancy, they did not include parental smoking at home in their model. It is not unlikely that among parents of children that were reported to have been watching television for longer, many of them were smoking in the presence of their child.

Adjustment for such additional factors is warranted before discussing the consequences of the study findings.