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.
Keywords: cognitive impairment; mortality; oldest-old; subdomain; subgroup; time-dependent Cox regression.
© 2021 The Authors. Brain and Behavior published by Wiley Periodicals LLC.