Functional status and mortality in community-dwelling older people.

Abstract

To the Editor: Functional status has been identified as an independent risk factor for poor results in rehabilitation programs, longer hospital stays, pneumonia severity, postsurgical morbidity, and mortality among institutionalized older people.1, 2 In this study we examined whether functional status is a reliable predictor of short-term overall mortality in community-dwelling older people. A prospective 4-year follow-up study was performed in older people living in a rural community of Tenerife (Canary Islands, Spain). All patients age 65 and older admitted to the Primary Care Center during the recruitment year were eligible for the study. All subjects underwent a comprehensive geriatric assessment, which included information about variables related to health status, cognitive functions and depression, family status, and support networks. The functional status was assessed according to the Katz activities of daily living (ADL) scale.3 It allows ranking the patient in one of seven categories, from A to G, where A indicates the most-independent score and G the most-dependent score. All statistical analysis was performed with respect to the baseline assessment. Every subject was followed up until either death or the end of the study. An initial bivariate Pearson's chi-square was performed to assess the association with death of the variables derived from the geriatric assessment. Then Kaplan-Meier survival curves were constructed and compared with the log-rank test. Lastly, Cox proportional hazard models were constructed to detect the effect on survival of different covariables, such as ADL impairment, age group, health status, specific illnesses, cognitive function, psychiatric disorders, social/family situation, and its interactions. Statistical significance was set at P < .05, and relative risk of death for each factor group was estimated at 95% confidence intervals. During the recruitment year, 189 patients age 65 and older (76 ± 7 years; mean ± standard deviation, with no differences per gender) were admitted to the study. Thirty-one subjects died during the study. In the bivariate analysis, the factors associated with mortality were age, heart disease, cognitive decline, and functional status (P < .001). The Kaplan-Meier survival curves showed that 4-year survival rate was inversely and significantly associated (P < .001) with the impairment in one or more ADLs (Figure 1). In the multivariate analysis, the association between survival and functional status proved to be independent of the presence of heart disease, cognitive deficits, absence of relative's support, and other social-structure variables. The relative death risk associated with an increasing impairment in ADLs (from independence to dependence on one or more ADLs), adjusted for the variables of illness, was 6.5 (95% CI = 5.3–7.2; P < .001). After adjusting the Cox model for age in 5-year intervals, the interaction age–ADL score was a predictive factor for short-term mortality. Moreover, death risk increased in each age group when the ADL score increased (Table 1). Lastly, the interaction between age, as a continuous variable, and an increasing ADL score (dependence on one or more than one daily activity) was a predictive factor for death, with relative risks of 1.02 (95% CI = 1.004–1.03; P = .037) and 1.03 (95% CI = 1.02–1.04; P < .001), respectively. Kaplan-Meier survival curves in non-institutionalized older people. A = independent subjects;> A = subjects dependent on one or more activities of daily living according to the Katz scale. A vs.> A (P < .001; log-rank test) The present study shows that, independent of age and health condition, functional status, assessed through the Katz ADL scale, is a predictive factor for short-term mortality in noninstitutionalized older people. This is especially noticeable for more functionally dependent subjects. Our results are in line with the findings by Ostbye et al.,4 who reported a significantly greater death rate in dependent older people than in independent ones. Using mortality predictors based on functional ability, we can develop methods that can help us improve health care and the process of decision making in clinical practice, as has been previously suggested1, 4 for hospitalized and nonhospitalized patients.