Abstract

Background Dietary protein may prevent or modulate the progression of frailty, by slowing down the decline of muscle mass, strength, and physical function with ageing. We aimed to examine the association between higher protein intake and transitions between frailty states. Methods The analytic sample included 27,128 participants aged 50 + from the UK Biobank cohort study. Physical frailty at baseline and follow-up was based on slow walking speed, unintentional weight loss, exhaustion, low physical activity, and weakness. Protein intake was assessed with web-based 24 h recalls on up to 5 occasions. The effect of protein intake on forward and backward transitions (and maintenance) between frailty states (non-frailty, pre-frailty, and frailty) and to death over a mean of 5 (max 16) years was examined with multi-state models. Results There were 5646 transitions from non-frail to pre-frail, 4187 from pre-frail to non-frail, 552 from pre-frail to frail, and 311 from frail to pre-frail. Middle-aged and older participants with higher protein intake (increments of 0.1 g/kg bodyweight/day and protein categories of < 0.8 (ref), 0.8 to < 1.0, 1.0 to < 1.2, >= 1.2 g/kg bodyweight/day) were less likely to progress from pre-frailty to frailty, and appeared to be more likely to recover from pre-frailty to non-frailty, with evidence of a dose-dependent relationship. E.g. For participants with protein intake of 0.8 to < 1.0, 1.0 to < 1.2 and >= 1.2, hazard ratios (95%CI) for incident frailty were 0.80 (0.71-0.91), 0.72 (0.63-0.81) and 0.68 (0.60-0.78), respectively, compared to < 0.8 g/kg bodyweight/day. Higher protein intake had no effect on recovery from frailty to pre-frailty. Conclusions Higher protein intake moderately reduced the risk for frailty incidence and may have increased the likelihood of recovery from pre-frailty in a dose-dependent manner in middle-aged and older adults. These findings may optimize strategies to prevent frailty in middle-aged and older adults and inform dietary protein guidelines in this population.