Impaired lung function, lung disease, and risk of incident dementia

Rationale: Growing evidence suggests that compromised lung health may be linked to dementia and worsening cognitive ability. Objectives: To test the hypothesis that impaired lung function or lung disease in midlife is associated with greater risk of incident dementia and mild cognitive impairment (MCI) later in life. Methods: A total of 14,184 Atherosclerosis Risk in Communities study participants who underwent spirometry and were asked about lung health (1987-1989) were followed. Dementia and MCI were defined by hospitalization diagnosis codes (1987-2013) in the whole cohort and with adjudication among 42% who attended a comprehensive neurocognitive examination (2011-2013). Measurements and Main Results: In analysis using adjudicated outcomes, odds of dementia or MCI were higher among participants with restrictive (multivariable-adjusted odds ratio, 1.58; 95% confidence interval, 1.14-2.19) and obstructive lung disease (multivariable-adjusted odds ratio, 1.33; 95% confidence interval, 1.07-1.64), compared with those without disease or respiratory symptoms. Associations were similar in analyses restricted to nonsmokers, and present for both Alzheimer's disease-related dementia and cerebrovascular etiologies. Low FEV1% predicted and FVC% predicted were also associated with increased dementia risk. Conclusions: Midlife lung disease and reduced lung function were associated with modestly increased odds of dementia and MCI later in life. Magnitudes of association were more pronounced for restrictive impairment than for obstructive lung disease. These associations were present in smokers and nonsmokers. If the observed associations are causal, policy and public health efforts to reduce smoking and improve air quality may have the added benefit of preventing the development of dementia and MCI.