Background: Previous studies reported a higher risk of cognitive decline and dementia amongst individuals with impaired lung function. However, many did not adjust for important confounders or did not include women and non-whites.
Methods: We studied 10 975 men and women aged 47–70 years (23% African-Americans) enrolled in the Atherosclerosis Risk in Communities Study. Pulmonary function tests and a cognitive assessment, including the Delayed Word Recall, the Digit Symbol Substitution, and the World Fluency Tests, were carried out in 1990–1992. Repeated cognitive assessments were performed in 1996–1998 for the entire cohort, and in 1993–1995, and 2004–2006 in 904 eligible individuals. Dementia hospitalization was ascertained through 2005.
Results: In analysis adjusted for lifestyles, APOE genotype, and cardiovascular risk factors, impaired lung function was associated with worse cognitive function at baseline. No association was found between lung function and cognitive decline over time. Impaired lung function at baseline was associated with higher risk of dementia hospitalization during follow-up, particularly amongst younger individuals. The hazard ratios (95% confidence intervals) of dementia hospitalization were 1.6 (0.9, 2.8) and 2.1 (1.2, 3.7) comparing the lowest with the highest quartile of forced expiratory volume in 1 s and forced vital capacity, respectively. Presence of a restrictive ventilatory pattern, but not of an obstructive pattern, was associated with reduced cognitive scores and higher dementia risk.
Conclusion: Reduced lung function was associated with worse performance in cognitive assessments and with an increased risk of dementia hospitalization. Future research should determine whether maintaining optimal pulmonary health might prevent cognitive impairment and dementia.