Longitudinal associations of socioeconomic position in childhood and adulthood with decline in lung function over 20 years: results from a population-based cohort of British men.

BACKGROUND: Associations of socioeconomic position with lung function are reported mostly from cross-sectional studies. The aim of this study was to investigate the associations between socioeconomic position both in adulthood and childhood with changes in lung function over a 20-year period.
METHODS: A socioeconomically representative cohort of 7735 British men aged 40-59 years was followed-up from 1978-1980 to 1998-2000. Lung function (height-standardised forced expiratory volume in 1 s (FEV(1)) and forced vital capacity (FVC)) was assessed at both time points in 4252 survivors. Adult socioeconomic position was derived from longest-held occupation in middle age and childhood socioeconomic position from father's longest-held occupation.
RESULTS: Both FEV(1) and FVC declined over time; the decline increased progressively from social class I (highest) to V (lowest); p for trend ≤ 0.0001. The mean difference in decline comparing manual versus non-manual groups was -0.13 litres (95% CI -0.16 to -0.10) for FEV(1) and -0.09 litres (95% CI -0.13 to -0.05) for FVC. These differences remained after adjustment for age, cigarette smoking, body mass index, physical activity and history of bronchitis. Similar differences in lung function decline were observed comparing manual with non-manual childhood social classes, although the differences were reduced by adjustment for adult social class and risk factors. Men in manual social classes in both childhood and adulthood had the greatest decline in lung function compared to those in non-manual groups in childhood and adulthood.
CONCLUSIONS: Socioeconomic position across the life course could have a significant impact on decline in lung function in later life. The role of environmental factors associated with socioeconomic position merits further exploration.