How far can we explain the social class differential in respiratory function? A cross-sectional population study of 21,991 men and women from EPIC-Norfolk
McFadden E., Luben R., Wareham N., Bingham S., Khaw KT.
The objective of this study is to investigate the association between occupational social class and respiratory function, as measured by forced expiratory volume in one-second (FEV 1 ). We examined the cross sectional relationship between lung function and social class in a population study of 21,991 men and women aged 39-79 years living in the general community in Norfolk, United Kingdom, recruited using general practice age-sex registers in 1993-1997. There was a significant socioeconomic gradient in age adjusted lung function with a difference of 0.37 in mean FEV 1 in men and 0.20 in women, respectively between social class I and V. The age adjusted OR for having poor lung function was 4.13 (95% CI 2.66-6.42) in men and 2.64 (95% CI 1.74-3.99) in women for social class V compared to I. This difference was substantially attenuated after adjustment for height, weight, smoking status, respiratory illness, educational level, living in a deprived area, physical activity and plasma vitamin C levels. There was a strong socioeconomic gradient in respiratory function. In men the gradient appeared to be largely explained by smoking status and height; in women a large part of the gradient was explained by potentially modifiable factors. This suggests that socioeconomic inequalities in respiratory function may be preventable or modifiable and highlights factors for further exploration. © 2009 Springer Science+Business Media B.V.