Protein density, carbohydrate quality, and frailty-state transitions among adults aged 50 years or older: a continuous-time multistate analysis of the health and retirement study

Background Frailty is a dynamic condition in which individuals may deteriorate, recover, remain stable, or die. Although healthier dietary patterns have been associated with a lower risk of frailty, less is known about their associations with specific frailty-state transitions. We examined whether a study-specific score emphasizing protein density and carbohydrate quality was associated with transitions between frailty states. Methods We linked the 2013 Health and Retirement Study nutrition assessment to repeated frailty assessments from 2014 to 2021 among participants aged 50 years or older. The study-specific score combined higher densities of protein, fiber, and whole-grain densities with lower densities of added-sugar and glycemic-load densities. Frailty was assessed using a published 28-item deficit-accumulation index. The primary continuous-time multistate model allowed baseline transition intensities to change at 2 and 4 years and adjusted for age, sex, education, body mass index (BMI), ethnicity, Hispanic ethnicity, smoking, alcohol consumption, and moderate and light physical activity. Dietary components were also examined individually and jointly. Results The primary analysis included 6,982 participants aged 50–102 years (mean, 69.0 years; 60.3% aged 65 years or older), with 25,108 person-state records and 1,487 deaths. Including the score improved model fit (likelihood-ratio [LR], 24.08; degrees of freedom [df], 7; p = 0.001). Each 1-standard deviation (SD) higher score was associated with lower robust-to-pre-frail intensity (hazard ratio [HR], 0.933; nominal 95% confidence interval [CI], 0.875–0.995) and pre-frail-to-death intensity (HR, 0.809; 95% CI, 0.662–0.989). Confidence intervals included 1 for the remaining worsening, recovery, and death transitions. No individual component association remained statistically significant after mutual adjustment and false-discovery-rate correction. Conclusion After comprehensive adjustment, a higher study-specific score was associated with lower robust-to-pre-frail and pre-frail-to-death intensities, but evidence for other transitions was inconclusive. The score remains unvalidated, and these findings do not establish a causal effect of diet on frailty transitions.