Low cognitive ability in early adulthood is associated with reduced lung function in middle age: the Vietnam experience study.

OBJECTIVE Reduced lung function has been linked to poorer cognitive ability later in life. In the present study, the authors examined the converse: whether there was a prospective association between cognitive ability in early adulthood and lung function in middle age. METHODS Participants were 4256 male Vietnam-era US veterans. Cognitive ability was assessed by the Army General Technical Test on enlistment when participants were, on average, 20 years old (range: 17-34). Data on ethnicity and place of service were extracted from army files. Smoking behaviour, alcohol consumption, basic socio-demographics and whether participants had a physician-diagnosed chronic disease were determined by telephonic interview in middle age in 1985. Forced expiratory volume in one second (FEV(1)) was measured by spirometry at a 3-day medical examination in 1986. Height and weight were also measured. RESULTS In linear regression models, poor cognitive ability in early adulthood was associated with reduced lung function in middle age, first adjusting for age and height, β=0.17, p<0.001, then additionally adjusting for circumstantial, socio-demographic, lifestyle and health factors, β=0.12, p=0.001. The same results were obtained when the analysis was confined to non-smokers. CONCLUSION Not only is lung function related to subsequent cognitive ability, but poor cognitive ability earlier in life is also associated with reduced lung function in middle age.