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

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.