Protein intake, physical activity and grip strength in European and North American community-dwelling older adults: a pooled analysis of individual participant data from four longitudinal ageing cohorts

Higher dietary protein, alone or in combination with physical activity (PA), may slow the loss of age-related muscle strength in older adults. We investigated the longitudinal relationship between protein intake and grip strength, and the interaction between protein intake and PA, using four longitudinal ageing cohorts. Individual participant data from 5584 older adults (52 % women; median: 75 years, IQR: 71 center dot 6, 79 center dot 0) followed for up to 8 center dot 5 years (mean: 4 center dot 9 years, SD: 2 center dot 3) from the Health ABC, NuAge, LASA and Newcastle 85+ cohorts were pooled. Baseline protein intake was assessed with food frequency questionnaires and 24-h recalls and categorized into < 0 center dot 8, 0 center dot 8-<1 center dot 0, 1 center dot 0-<1 center dot 2 and >= 1 center dot 2 g/kg adjusted body weight (aBW)/d. The prospective association between protein intake, its interaction with PA, and grip strength (sex- and cohort-specific) was determined using joint models (hierarchical linear mixed effects and a link function for Cox proportional hazards models). Grip strength declined on average by 0 center dot 018 SD (95 % CI: -0 center dot 026, -0 center dot 006) every year. No associations were found between protein intake, measured at baseline, and grip strength, measured prospectively, or rate of decline of grip strength in models adjusted for sociodemographic, anthropometric, lifestyle and health variables (e.g., protein intake >= 1 center dot 2 v center dot < 0 center dot 8 g/kg aBW/d: beta = -0 center dot 003, 95 % CI: -0 center dot 014, 0 center dot 005 SD per year). There also was no evidence of an interaction between protein intake and PA. We failed to find evidence in this study to support the hypothesis that higher protein intake, alone or in combination with higher PA, slowed the rate of grip strength decline in older adults.

Automated summary

This study aimed to investigate the relationship between protein intake and grip strength, as well as the interaction between protein intake and physical activity, in relation to the rate of grip strength decline in older adults. The findings showed no evidence to support the hypothesis that higher protein intake, alone or in combination with higher physical activity, slowed the rate of grip strength decline in older adults.