Lifetime body mass index and grip strength at age 46 years: the 1970 British Cohort Study

Background: Ongoing rises in obesity prevalence have prompted growing concerns about potential increases in the burden of age-related musculoskeletal conditions including sarcopenia and sarcopenic obesity. This is of particular concern for future generations of older adults who have lived more of their lives in an obesogenic environment than current generations of older adults. We aimed to study longitudinal associations between body mass index (BMI) and grip strength in midlife using data from a large population-based sample, the 1970 British Cohort Study (BCS70). Methods: BCS70 participants with valid measures of maximum grip strength at age 46y were included in analyses (3,671 males (49%) and 3,876 females (51%)). Using sex-specific linear regression models we examined associations of: i) BMI at ages 10, 16, 30 and 46y; ii) body fat percentage (BF%) and waist-hip ratio at age 46y; iii) BMI gains between 10-16, 16-30 and 30-46; and iv) age at onset of obesity, with grip strength. Results: At age 46y, mean (SD) grip strength was 48.10kg (8.98) in males and 29.61kg (5.81) in females. Higher BMI at all ages was associated with stronger grip and the scale of associations were greater in males than females from age 16 onwards (psex interactions<0.01). For example, in fully-adjusted models a 1 standard deviation increase in BMI at age 16 was associated with mean differences in grip strength at age 46y of 1.41kg (95% CI:1.07,1.75) in males and 0.72kg (0.53,0.91) in females. Higher BF% at age 46 was also associated with stronger grip in both sexes. Greater gains in BMI between ages 10 and 16 were associated with stronger grip in both sexes but subsequent gains in BMI were only associated with stronger grip in males. Associations of greater length of exposure to obesity and stronger grip were also more consistent among males than females. For example, in fully-adjusted models, mean grip strength at age 46y of males and females who had been obese since age 10 or 16y was 4.39kg (1.85, 6.93) and 1.25kg (-0.18, 2.69) ...