Protein Intake and Disability Trajectories in Very Old Adults: The Newcastle 85+ Study

OBJECTIVES: To determine whether protein intake is associated with better disability trajectories in the oldest adults (≥85) and whether muscle mass and muscle strength would partially mediate this. DESIGN: Prospective cohort study. SETTING: Newcastle‐upon‐Tyne and North Tyneside, United Kingdom. PARTICIPANTS: Community‐dwelling older adults aged 85 at baseline (N=722). METHODS: Protein intake was estimated using two 24‐hour multiple‐pass recalls at baseline. Disability was measured as difficulty performing 17 activities of daily living at baseline and 18, 36, and 60 months. Trajectories were derived using mortality‐adjusted group‐based trajectory modelling. The effect of protein intake (g/kg of adjusted body weight (aBW)/d) on disability trajectories was examined using multinomial logistic regression. RESULTS: Participants had 4 distinct disability trajectories (between the ages of 85 and 90: constant very low (AT1), mild (AT2), moderate (AT3), and severe (AT4). Each unit increase in protein (g) per kg of aBW/d was associated with greater odds of AT1 (odds ratio (OR=7.97, 95% confidence interval (CI)=1.96–32.43, p = .004) and AT2 (OR=3.28, 95% CI=1.09–9.87, p = .03) than of AT4 over 5 years in models adjusted for selected covariates. Participants with protein intake of 1.0 g/kg aBW/d or more were more likely to belong to AT1 (OR=3.65, 95% CI=1.59–8.38, p = .009) and AT2 (OR=2.12, 95% CI=1.16–3.90, p = .01) than to AT4. CONCLUSION: Higher protein intake, especially 1.0 g/kg aBW/d or more, was associated with better disability trajectories in the oldest adults. These findings will inform new dietary strategies to support active, healthy ageing. J Am Geriatr Soc 67:50–56, 2019.