Title:
Chronic obstructive pulmonary disease, cognitive impairment, and development of disability: the health and retirement study.

Abstract:
The relationship between chronic obstructive pulmonary disease (COPD) and cognitive impairment in leading to disability has not been characterized.
We aimed to investigate the prevalence and cumulative incidence of disability among adults with and without COPD and the association of COPD and cognitive impairment with disability.
We analyzed 2006-2008 waves of the Health and Retirement Study, a nationally representative longitudinal health survey. COPD was self-reported. Prevalent disability was defined as baseline dependency in one or more activities of daily living (ADLs) and incident disability as one or more additional ADL dependencies. We used a validated performance-based measure of cognition to identify dementia and mild cognitive impairment. Covariates included seven chronic diseases, four geriatric syndromes, and sociodemographics. We used logistic regression to test associations between COPD, cognitive status, and prevalent/incident disability.
Of 17,535 participants at least 53 years of age in wave 2006 (representing 77.7 million Americans), 9.5% reported COPD and 13.5% mild cognitive impairment; 17.5% of those with COPD had mild cognitive impairment. Prevalent disability for COPD was 12.8% (5.2% for no-COPD, P < 0.001). An additional 9.2% with COPD developed incident disability at 2 years (4.0% for no-COPD, P < 0.001). In adjusted models, COPD was associated with baseline (odds ratio, 2.0) and incident disability (odds ratio, 2.1; adjusted for baseline disability). Cognitive impairment had an additive effect to COPD. The COPD-disability association, prevalent/incident, was of similar or greater magnitude than that of other chronic diseases (e.g., stroke, diabetes). The associations were maintained in sensitivity analyses using alternative definitions of disability (dependency in two or more ADLs, dependency in instrumental ADLs), and in analysis excluding respondents with dementia.
Both COPD and mild cognitive impairment increase the risk of disability. The risk conferred by COPD is significant and similar or higher than other chronic diseases.