Age-related changes in anthropometric measurements, body composition, and physical function among middle-aged and...

To quantify annual changes and develop population-normalized aging curves for height, body weight, and grip strength according to specific birth cohorts.

This longitudinal study analyzed data from the National Institute for Longevity Sciences - Longitudinal Study of Aging, following 1901 community-dwelling adults aged 40-79 years for up to 12 years. Annual changes in height, body weight, body mass index (BMI), body fat percentage, skeletal muscle mass, and grip strength were assessed by sex using linear mixed-effects models. Birth cohort-specific reference values according to sex were developed using participants who participated in at least one wave between 1997 and 2022 (n = 1990) with generalized additive mixed models.

Significant negative follow-up years × age interactions were observed for height, body weight, BMI, skeletal muscle mass, and grip strength in men (all p-values < 0.001) and for height, body weight, BMI, body fat percentage, and skeletal muscle mass in women (all p-values < 0.01). Grip strength began declining preceding any significant change in other indicators. For height and grip strength, birth cohort-specific reference values for age-related changes showed a gradual decline with age in both sexes, with more recent birth cohorts being consistently taller but having weaker grip strength than earlier cohorts. Men experienced slight weight increases until ages 60-70 years, followed by a decline. Women maintained a stable weight until age 60 years before declining.

These reference values provide evidence-based tools for detecting age-related changes in body composition and function among relatively healthy participants and guiding preventive interventions in clinical and community settings.