Serum Vitamin D and Age-Related Muscle Loss in Afro-Caribbean Men: The Importance of Age and Diabetic Status

Background Prospective studies examining the potential association of vitamin D with age-related muscle loss have shown inconsistent results. Objective To examine the association between baseline serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH) 2 D), and prospective change in lean mass with aging in African ancestry population. We also determined if associations were modulated by age and diabetes mellitus (DM). Design: Prospective observational cohort study. Setting Data were collected from a random sub-sample of 574 men, participants of the Tobago Bone Health Study (TBHS). Participants 574 Afro-Caribbean men, aged 43+ years (mean age: 59.1 ± 10.5), who were randomly selected as the participants in both the baseline and the follow-up visits. Measurements Baseline fasting serum 25(OH)D was measured using liquid chromatography mass spectrometry (LC-MS/MS), and and 1,25(OH) 2 D was measured using radioimmunosassay (RIA). Changes in dual-energy X-ray absorptiometry (DXA)-measured appendicular lean mass (ALM), and total body lean mass (TBLM) were measured over an average of 6.0 ± 0.5 years. The associations of 25(OH) D and 1,25(OH) 2 D with ALM and TBLM were assessed by multiple linear regression model after adjusting for potential confounders. Results When stratifying all men into two groups by age, greater baseline 25(OH) D and 1,25(OH) 2 D levels were associated with smaller losses of ALM and TBLM in older (age 60+ years) but not in younger (age 43–59 years) men. When stratifying by DM status, the associations of 25(OH)D and 1,25(OH) 2 D with declines in ALM and TBLM were statistically significant only in prediabetic, but not among normal glycemic or diabetic men. Conclusion Higher endogenous vitamin D concentrations are associated with less lean mass loss with aging among older and prediabetic Afro-Caribbean men independent of potential confounders. Our findings raise a possibility that maintaining high serum vitamin D level might be important for musculoskeletal health in elderly and prediabetic African ancestry men.