Background: several studies have found that lung function correlates with survival in older people. We examined secular trends in lung function and its relation to survival in Swedish 75 year olds.
Method: representative samples from the general population in Gothenburg, Sweden, were examined at the age of 75 in 1976-77 (n = 743) and 2005-06 (n = 765) with comprehensive somatic and psychiatric examinations. Lung function was measured as peak expiratory flow (PEF).
Results: the mean PEF was higher in 75 year olds examined 2005-06 compared with those examined 1976-77 both among women (339 versus 307 l/min; P < 0.001) and men (490 versus 400 l/min, P < 0.001). The birth cohort effect was still significant after adjusting for a number of confounders. PEF correlated with survival between age 75 and 78 years among those examined in 1976-77 both in women (OR per 10 l/min increase in PEF = 1.112, 95% CI: 1.047-1.182) and in men (OR = 1.040, 95% CI: 1.015-1.066), but not in those examined 2005-06 (women: OR = 1.071, 95% CI: 0.965-1.188; men: OR = 1.000, 95% CI: 0.957-1.046).
Conclusion: we found better lung function in the later-born cohort of 75 year olds, which was only partially explained by changes in smoking, height and weight, physical activity, socio-economic/educational factors and pulmonary/cardiovascular morbidity. The association between better lung function and short-term survival was strong in 1976-77, but had disappeared in 2005-06. More studies are needed to elucidate the role of lung function for long-term survival and identify other factors that explain the secular trends in lung function.