Clusters of functional domains to identify older persons at risk of disability

Aim: To date, there is no consensus on which set of variables should be used to identify older persons at risk of disability in activities of daily living. The present study aimed to: (i) evaluate how different deficits cluster in a population of community-dwelling older persons; and (ii) investigate whether the discriminative capacity of physical performance measures towards the development of disability might be improved by adding psychological, social and environmental indicators. Methods: Data are from 709 non-disabled older persons participating in the "Invecchiare in Chianti" study. We carried out a cluster analysis of 12 deficits in multiple functional domains, selected from the available frailty assessment instruments. Then, participants were assigned to a group, based on the obtained clusters of variables. For each group, we measured the prognostic capacity and the predictive ability for 6-year disability. Results: The analysis showed a "physical" cluster (including weight loss, reduced grip strength/gait speed/physical activity, impaired balance, environmental barriers) and a "psychosocial" cluster (e.g. living alone, depression, low income). Thus, participants were classified into four groups according to the presence of a physical and/or psychosocial cluster. Compared with the "fit" group, the relative risks of becoming disabled in the "physical," "psychosocial" and "mixed" deficit groups were 2.23 (95% CI 0.71-7.00), 1.52 (95% CI 0.62-3.75) and 6.37 (95% CI 2.83-14.33), respectively. The positive and negative predictive values for the "physical," "psychosocial" and "mixed" deficit groups were, respectively, 9% and 87%, 6% and 83%, and 27% and 94%. Conclusions: As expected, physical and psychosocial deficits cluster predominantly into different groups. Even when both are considered simultaneously, the ability to predict incident disability is still insufficient.