Effects of cognitive impairment and loss of physical capacities on survival of the elderly

This study investigates the effects of cognitive impairment and loss of physical capacity on the survival rates of the elderly in Taiwan. Data used for this research were obtained from a longitudinal study in northern Taiwan, where 1,434 elderly respondents were randomly selected and were interviewed in 1993 and 1996. Respondents were categorized into four groups: those with physical disability, those with cognitive impairment, those with neither condition and those with both conditions. The survival rates of these four groups were analyzed and compared. The effects of cognitive impairment and physical disability were assessed separately and jointly. Within the study period, we found that elderly persons with both conditions had the lowest survival rate (0.54, 95% confidence interval (CI) 0.35-0.73), while those with neither condition had the most favorable survival rate (0.92, 95% CI 0.90-0.93). Results from the Cox proportional hazard model showed that physical disability had a significantly adverse effect on the risk of mortality (relative risk 2.5, 95% CI 1.5-4.2), while cognitive impairment did not. Our results are consistent with previous findings which have shown that the decline in physical function affects mortality more than the decline in cognitive function.