Chronic obstructive pulmonary disease and cognitive impairment in the Chinese elderly population: a large national survey

BACKGROUND Previous studies suggested an association between chronic obstructive pulmonary disease (COPD) and cognitive impairment, mostly in developed countries. There is no evidence available on the association between these two common chronic disorders in the elderly people in People's Republic of China where the population is aging rapidly. METHODS The study population was randomly selected from a nationally representative Disease Surveillance Point System in People's Republic of China. A standardized questionnaire was administered by trained interviewers during a face-to-face interview in the field survey conducted in 2010-2011. Cognitive function was assessed using the Mini-Mental State Examination. COPD was measured by self-report and the Medical Research Council respiratory questionnaire was used to assess respiratory symptoms. A multivariate logistic regression model was applied to examine the association between COPD and cognitive impairment with adjustment for potential confounding factors. RESULTS A total of 16,629 subjects aged over 60 years were included in the study. The prevalence of cognitive impairment was 9.4% (95% confidence interval [CI] 7.7, 11.1). Chronic phlegm was associated with significantly higher prevalence of cognitive impairment in models adjusted for age, sex, marital status, geographic region, urban/rural, education, smoking status, alcohol drinking, and indoor air pollution (odds ratio [OR] 1.46, 95% CI 1.11, 1.93). Chronic respiratory symptoms and self-reported COPD were strongly related to cognitive impairment in urban areas. There were no significant effect modifications for sex, regions, educational level, smoking status, and alcohol drinking. CONCLUSION There was strong association between COPD and cognitive impairment in urban Chinese elderly population.