Association of Cognitive Impairment and Elderly Mortality: Differences of two cohorts ascertained 6-years apart in China
Cognitive impairment is a major contributor to mortality among the elderly. However, the trend between cognitive impairment and mortality with time is understudied. We aim to evaluate the differences in associations of cognitive impairment with all-cause mortality and explore the relationship of cognitive impairment with mortality in different age and sex groups in two cohorts ascertained 6 years apart in China. Methods : A total of 13906 and 13873 Chinese elderly aged 65 years and older were
... rs and older were included in the 2002-2008 and 2008-2014 cohorts from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Mortality data was ascertained from interviews with family members or relatives of participants. Cognitive function, evaluated by the Mini-Mental State Examination (MMSE), were defined by different cut-offs taking educational background into account. Cox models were used to explore the relationship of cognitive impairment with mortality. Results: For the 2002-2008 and 2008-2014 cohorts, the total follow-up times were 55,277 and 53,267 person-years, and the mean (SD) age were 86.5 (11.6) and 87.2 (11.3) years, respectively. Compared to normal cognition, severe cognitive impairment was independently associated with higher mortality risk after controlling for potential confounders, with hazard ratios (HRs) of 1.48 (95% confidence interval [CI], 1.39-1.57) in 2002-2008 cohort and 1.32 (95% CI, 1.25-1.41) in 2008-2014 cohort. The trend of cognitive impairment with risk of all-cause mortality decreased from 2002-2008 to 2008-2014 cohort. The association of cognitive impairment and mortality was decreased with age in the two cohorts. Conclusions : Cognitive impairment evaluated by MMSE was associated with increased risk of mortality and the association decreased with the passage of time during the two 6-year cohorts; this advocates that periodic screening for cognitive impairment among the 3 elderly is warranted.