Developing and evaluating a frailty index for older South Africans - findings from the HAALSI study

Background: despite rapid population ageing, few studies have investigated frailty in older people in sub-Saharan Africa. We tested a cumulative deficit frailty index in a population of older people from rural South Africa. Methods: analysis of cross-sectional data from the Health and Ageing in Africa: Longitudinal Studies of an INDEPTH Community (HAALSI) study. We used self-reported diagnoses, symptoms, activities of daily living, objective physiological indices and blood tests to calculate a 32-variable cumulative deficit frailty index. We fitted Cox proportional hazards models to test associations between frailty category and all-cause mortality. We tested the discriminant ability of the frailty index to predict one-year mortality alone and in addition to age and sex. Results: in total 3,989 participants were included in the analysis, mean age 61 years (standard deviation 13); 2,175 (54.5%) were women. The median frailty index was 0.13 (interquartile range 0.09–0.19); Using population-specific cutoffs, 557 (14.0%) had moderate frailty and 263 (6.6%) had severe frailty. All-cause mortality risk was related to frailty severity independent of age and sex (hazard ratio per 0.01 increase in frailty index: 1.06 [95% confidence interval 1.04–1.07]). The frailty index alone showed moderate discrimination for one-year mortality: c-statistic 0.68–0.76; combining the frailty index with age and sex improved performance (c-statistic 0.77–0.81). Conclusion: frailty measured by cumulative deficits is common and predicts mortality in a rural population of older South Africans. The number of measures needed may limit utility in resource-poor settings.Dr Barker and Professor Witham acknowledge support from the NIHR Newcastle Biomedical Research Centre. ANW is supported by the Fogarty International Centre of the National Institutes of Health under Award Number K43TW010698. National Institutes of Ageing (NIH) grant 1P01AG041710-01A1 National Dept of Science and Innovation (via South African Medical Research Council); Wellcome Trust (058893/Z/99/A; 069683/Z/02/Z; 085477/Z/08/Z; 085477/B/08/Z)