Developmental factors associated with decline in grip strength from midlife to old age: a British birth cohort study
Maintenance of muscle strength is important for healthy ageing, protecting against chronic disease and enabling independent living. We tested whether developmental factors were associated with grip strength trajectories between 53 and 69 years, and operated independently or on the same pathway/s as adult factors, in 3058 participants from a British birth cohort. Grip strength (kg) at ages 53, 60-64 and 69, was analysed using multilevel models, testing for age and sex interactions, to estimate associations with developmental factors (birthweight, growth parameters, motor and cognitive development) and childhood socioeconomic position (SEP) and investigate potential adult mediators. Heavier birthweight, beginning to walk on time, later puberty and greater weight 0-26 years in men, and earlier age at first standing in women, were associated with stronger grip but not with its decline; these associations were independent of adult factors. The slower decline in grip strength (by 0.068kg/year, 95% confidence interval (CI) 0.024,0.11 per 1SD, p=.003) in men with higher childhood cognition was attenuated by adult verbal memory which became increasingly positively associated with grip strength at older ages. Thus grip strength may increasingly reflect neural ageing processes. Targeting developmental factors to promote muscle development should increase the chance of independence in old age.