Background: Fried's frailty phenotype is defined by five criteria: exhaustion, unexplained weight loss, weakness, slowness and low physical activity. Prefrailty (PF) meets one or two criteria. PF is of interest as a target for preventative interventions, but it is not known if it is a homogenous syndrome.
Objective: to compare the longitudinal trajectories of two PF groups: one defined by exhaustion and/or unexplained weight loss (PF1) and one defined by one or two of the following: weakness, slowness, low physical activity (PF2).
Design and setting: population-based longitudinal study of ageing.
Subjects: One-thousand four-hundred seventy-six PF participants aged ≥50 years from wave 1 of the study (2010), followed 2-yearly over four longitudinal waves (2012, 2014, 2016, 2018).
Methods: generalised estimating equations (GEEs) were used to assess the effect of PF type across waves to predict cumulative mortality and disability in basic activities of daily living (ADL) and independent ADL (IADL), adjusting for baseline characteristics (age, sex, education, living alone, self-rated health, comorbidity, body mass index).
Results: in wave 1, there were 503 PF1 and 973 PF2 participants. By wave 5, 38 (7.6%) PF1 and 145 (14.9%) PF2 participants had died. In PF1 participants, mean numbers of ADL and IADL disabilities both increased from 0.1 to 0.2 from wave 1 to wave 5, whilst in PF2 increases were from 0.2 to 0.5. Adjusted GEE models suggested significantly divergent trajectories of IADL disability by wave 2, ADL disability by wave 3 and mortality by wave 3.
Conclusion: PF may not be a homogenous biological syndrome.
Keywords: disability; frailty; longitudinal studies; mortality; older people; phenotype.
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