Background: frailty fluctuations, that is, within-person up and down deviations from individual long-term frailty index trajectories represent a hitherto both conceptually and empirically untapped facet of frailty among older adults.
Objective: to assess the size of frailty fluctuations in old age and their association with frailty levels, frailty growth as well as sex and socio-economic position.
Methods: a total of 18,704 biannual observations from 4,514 community-dwelling older adults (65+) in 10 European countries over 12 years from the Survey of Health, Ageing and Retirement in Europe (SHARE) were analysed. A frailty index was constructed based on 50 items. Long-term frailty trajectories and fluctuations were modelled simultaneously using Bayesian mixed-effects location-scale regression models.
Results: frailty index fluctuations were non-negligible among older adults, amounting to 0.04/0.05 FI or 2.0/2.5 health deficits on average. 30% of fluctuations were between 0.04 and 0.1 FI (2 and 5 health deficits) and 8% were larger than 0.1 FI (5 health deficits). Fluctuations increased with age and frailty levels, and were higher among women, those with low socio-economic position (education) and individuals who died during follow-up.
Conclusions: frailty index fluctuations refer to instabilities in an older person's health status and represent a hitherto untapped but relevant aspect of vulnerability in old age. Future analysis of frailty fluctuations should be based on a larger number of repeated observations with shorter time intervals.
Keywords: fluctuations; frailty; intra-individual variability; mixed-effects location-scale regression model; older adults; socio-economic position.
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