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

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.

Prospective cohort study.

Newcastle-upon-Tyne and North Tyneside, United Kingdom.

Community-dwelling older adults aged 85 at baseline (N=722).

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.

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.

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.