A prospective study of chronic obstructive pulmonary disease and the risk for mild cognitive impairment

Abstract

Importance: Previous studies suggest cross-sectional associations between a diagnosis of chronic obstructive pulmonary disease (COPD) and mild cognitive impairment (MCI). However, few studies have assessed whether COPD, a potentially modifiable factor, is associated with an increased risk for MCI and whether the relation is specific to the type of MCI.

Objective: To investigate whether a diagnosis of COPD and duration of COPD are associated with an increased risk for incident MCI and MCI subtypes (amnestic MCI [A-MCI] and nonamnestic MCI [NA-MCI]).

Design, setting, and participants: A prospective population-based cohort from the Mayo Clinic Study on Aging. We included 1425 cognitively normal individuals aged 70 to 89 years who were randomly selected from Olmsted County, Minnesota, on October 1, 2004, using the medical records linkage system. At baseline and every 15 months thereafter, participants underwent assessment with a nurse interview, neurologic examination, and neuropsychological testing. A diagnosis of COPD was confirmed via medical record review. A baseline diagnosis of COPD and duration of COPD were examined as risk factors for MCI and MCI subtypes using Cox proportional hazards models and adjusting for demographic variables and medical comorbidities, with age as the time scale.

Exposure: A baseline diagnosis of COPD and duration of COPD.

Main outcomes and measures: Incident MCI, A-MCI, and NA-MCI.

Results: Of the 1425 participants with normal cognition at baseline, 370 developed incident MCI. The median duration of follow-up was 5.1 years (interquartile range, 3.8-5.4 years). A diagnosis of COPD significantly increased the risk for NA-MCI by 83% (hazard ratio, 1.83 [95% CI, 1.04-3.23]), but not of any MCI or A-MCI in multivariate analyses. We found a dose-response relationship such that individuals with COPD duration of longer than 5 years at baseline had the greatest risk for any MCI (hazard ratio, 1.58 [95% CI, 1.04-2.40]) and NA-MCI (2.58 [1.32-5.06]).

Conclusions and relevance: A diagnosis of COPD is associated with an increased risk for MCI, particularly NA-MCI. We have found a dose-response relationship between COPD duration and risk for MCI. These findings highlight the importance of COPD as a risk factor for MCI and may provide a substrate for early intervention to prevent or delay the onset and progression of MCI, particularly NA-MCI.

Figure 1. Adjusted Kaplan-Meier plots of COPD and risk of MCI

Figure 1A shows the relationship between COPD (Yes/No) and percent-free survival of MCI. Figure 1B shows the relationship between COPD duration (>5 years vs. less) or no COPD and percent-free survival of MCI with age as the timescale.