Co-presence of multimorbidity and disability with frailty: an examination of heterogeneity in the frail older population

Background: Frailty is often associated with multimorbidity and disability. Objectives: We investigated heterogeneity in the frail older population by characterizing five subpopulations according to quantitative biological markers, multimorbidity and disability, and examined their association with mortality and nursing home admission. Design: Observational study. Participants: Participants (n= 4,414) were from the population-based Age Gene/Environment Susceptibility Reykjavik Study. Measurements: Frailty was defined by >= 3 of five characteristics: weight loss, weakness, reduced energy levels, slowness and physical inactivity. Multimorbidity was assessed using a simple disease count, based on 13 prevalent conditions. Disability was assessed by five activities of daily living; participants who had difficulty with one or more tasks were considered disabled. Differences among frail subpopulations were based on the co-presence of multimorbidity and disability. Differences among the following subpopulations were examined: 1) Non-frail (reference group); 2) Frail only; 3) Frail with disability; 4) Frailty with multimorbidity; 5) Frail with disability and multimorbidity. Results: Frailty was present in 10.7% (n= 473). Frailty was associated with increased risk for mortality (OR 1.40; 95% CI 1.15-1.69) and nursing home admission (OR 1.50; 95% CI 1.16-1.93); risks differed by subpopulations. Compared to the non-frail, the frail only group had poorer cognition and increased inflammation levels but did not have increased risk for mortality (OR 1.40; 95% CI 0.84-2.33) or nursing home admission (OR 1.01; 95% CI 0.46-2.21). Compared to the non-frail, the other frail subpopulations had significantly poorer cognition, increased inflammation levels, more white matter lesions, higher levels of calcium, glucose and red cell distribution width and increased risk for mortality and nursing home admission. Conclusions: The adverse health risks associated with frailty in the general older adult population may primarily be driven by increased disease burden and disability