The association between the planetary health diet index (PHDI) and muscular dystrophies: A mediating role of phenotypic age.

To address the challenges posed by global aging and changing dietary habits, understanding the potential impact of healthy dietary patterns on diseases such as muscular dystrophies (MDs) and aging is crucial. The planetary health diet index (PHDI) is a dietary scoring system designed to balance human health and environmental sustainability by promoting the consumption of plant-based foods while reducing the intake of red meat, sugar, and highly processed foods. Additionally, phenotypic age is a composite measure based on multiple clinical biomarkers used to assess an individual's biological age. This study examines the relationship between PHDI and MDs and evaluates whether phenotypic age moderates this association. This study conducted a cross-sectional analysis of 2951 participants from the 2011 to 2018 National Health and Nutrition Examination Survey database. Subgroup analysis, restricted cubic splines, and multivariable logistic regression were employed to investigate the association between PHDI and the prevalence of MDs. Additionally, mediation analysis was performed to explore potential associations between phenotypic age, PHDI, and MDs. A total of 2951 participants were included in this study, of whom 224 had MDs. After adjusting for all variables using multivariable logistic regression, each 10-point increase in PHDI was associated with a 15% reduction in MDs prevalence (odds ratio [OR] = 0.85, 95% confidence interval [CI]: 0.73-0.99), while each one-unit increase in phenotypic age was associated with a 7% increase in MDs prevalence (OR = 1.07, 95% CI: 1.01-1.14). Additionally, phenotypic age decreased as PHDI increased (β = -0.31, 95% CI: -0.53 to -0.10). Mediation analysis indicated that phenotypic age statistically accounted for a proportion of the observed association between PHDI and MDs in this cross-sectional population. Adherence to the planetary health diet guidelines may reduce the prevalence of MDs and slow biological aging. Furthermore, phenotypic age may partially account for the observed cross-sectional association between dietary quality and MDs, highlighting a potential link between diet, biological aging, and muscle health.