Frailty Prevalence, Incidence, and Association with Incident Disability in the Italian Longitudinal Study on Aging

Abstract

Introduction: Data on frailty frequency are heterogeneous and mostly based on cross-sectional studies. Little is known about frailty development and progression over time. Our aim was to conduct a systematic analysis of frailty prevalence and incidence in a large cohort of older adults and to evaluate the association with incident disability, in order to tackle the current paucity and fragmentation of longitudinal data on frailty.

Methods: As secondary analysis of the Italian Longitudinal Study on Aging (ILSA) population-based cohort (n = 5,632, 65-84), frailty status was operationalized according to Fried criteria (n = 2,457). Weighted prevalence and incidence rates were calculated at each ILSA wave (T0 1992-1993, T1 1995-1996, T2 2000-2001). The association with incident disability in Activities of Daily Living (ADL) or Instrumental Activities of Daily Living (IADL) was investigated through Cox proportional hazard models, controlling for possible confounders.

Results: Prevalence of frailty and pre-frailty at baseline (mean age 71.6 years; women 58.9%) were 4.0% (95% confidence interval [CI]: 3.4-4.6) and 44.6% (95% CI: 43.1-46.1), respectively. Incidence rates per 1,000 person-years for the T0-T1 interval were 7.3 (95% CI: 5.2-9.3) for frailty and 83.7 (95% CI: 73.6-93.8) for pre-frailty. Prevalence and incidence of frailty, and to a lesser degree of pre-frailty, were overall higher for women and increased with age, yet no increasing trend with advancing age was detected for pre-frailty incidence. Frailty incidence rates were significantly higher among pre-frail than non-frail individuals at follow-up entry. After full adjustment, being frail markedly increased the risk of incident disability in ADL (hazard ratio [HR] 3.58, 95% CI: 1.97-6.52) and IADL (HR 2.56, 95% CI: 1.58-4.16) over a 4-year period.

Discussion/conclusion: According to our findings, frailty is common among older people and is a strong and independent predictor of disability. Further research on factors and characteristics related to frailty progression, and especially remission, over time is crucial to calibrate effective public health preventive measures.

Keywords: Aging; Cohort study; Disability; Epidemiology; Frailty.