Cognitive impairment and all‐cause mortality among Chinese adults aged 80 years or older

Objectives The oldest‐old (aged ≥80 years) are the fastest growing population segment and age is related to cognitive impairment. We aimed to estimate the association between cognitive impairment and all‐cause mortality, in addition to the relationship with different cognitive subdomains among the oldest‐old in China. Methods We analyzed 25,285 participants recruited from 22 out of 30 provinces in the Chinese Longitudinal Healthy Longevity Survey (CLHLS) from 1998 to 2008, with mortality follow‐up until 2014. Cognitive function was measured by the Chinese‐version 30‐item Mini‐Mental State Examination (MMSE), classified as no (MMSE score: 25–30), mild (18–24), moderate (10–17), and severe (0–9) impairment. We used time‐dependent Cox model to evaluate the relationship between time‐varying cognition and mortality. Results The relationship between cognition and mortality showed a dose–response pattern among the overall population. Compared to those with no impairment, participants with moderate (HR = 1.41, 95% CI 1.28–1.56) and severe (HR = 1.77, 95% CI 1.59–1.96) cognitive impairment showed increased mortality risk. Impairment in the subdomain of orientation was independently associated with increased mortality risk (HR = 1.20, 95% CI 1.05–1.36) among participants without overall cognitive impairment. Urban and rural residents had similar mortality risk. Conclusions A consistent dose–response pattern existed between cognitive impairment and all‐cause mortality. Orientation was associated with mortality in the population without cognitive impairment. Similar mortality regardless of residence areas indicated scarce health care and treatment for cognitive impairment in China from 1998 to 2014.
Based on 25,285 Chinese participants 80 years or older, we found a clear negative dose–response relationship between the severity of time‐varying cognitive impairment and the probability of survival for both female and male and the total population. The relationship between cognition and mortality was similar for urban and rural residents, and the dose–response pattern disappeared in the highest educated group. The orientation subscale was associated with mortality risk independent of the overall MMSE score.