Cognitive impairment, activities of daily living, and mortality among the elderly in rural South Korea : Kangwha cohort study

Abstract

Purpose

The purpose of this study is to examine the effects through the various combinations of cognitive impairment and ADL disability with mortality due to all-cause, vascular diseases, cancer, and senility, in a 14.5-year prospective cohort among community-dwelling elderly Koreans.

Methods

The cohort involved 2,501 participants ages 64 years and older starting from July 1994 to December 2008. Chi-squared tests and one-way analysis of variance (ANOVA) were performed to compare differences between the groups. Cox proportional hazards models were used to evaluate the associations among cognitive performance, ADL, and mortality.

Results

There were 1,481 deaths during the follow-up. Mortality risks due to all-cause, vascular diseases, and senile were significantly associated with cognitive impairment and ADL disability. No association was found between cancer mortality and cognitive impairment or ADL disability. Domain-specific cognitive impairment or task-specific ADL disability was diversely related with cause-specific mortality. When cognitive impairment and ADL disability were combined, the Synergy index increased due to interaction. The effects indicated all-cause (HR=2.72), vascular disease (HR=3.40), and senility (HR=1.58).

Conclusion

Cognitive impairment and ADL disability are important risk factors towards the increase of mortality due to all-cause, vascular disease, and senility, but cancer didn’t suggest concrete correlation. Domain-specific cognitive function and task-specific ADL predicted the mortality risk. Combining cognitive impairment and ADL disability showed a higher risk for coexisting variables than for cognitive impairment or ADL disability alone.