The association between serum vitamin D and body composition in black South African postmenopausal HIV positive women on antiretroviral therapy

Abstract

Background: HIV/AIDS and highly active antiretroviral therapy (HAART) alter bodily processes, including vitamin D metabolism. Altered vitamin D metabolism is associated with adiposity and bone loss. Objective: To determine the association between serum 25-hydroxyvitamin D (25(OH)D) and body composition in black South African postmenopausal HIV-positive women on HAART. Methods: This two-year longitudinal study is part of a larger prospective study (n=120) in the North West Province of South Africa. Measures included serum 25(OH)D concentration, bone mineral density (BMD) at three sites, lean mass and percent body fat (%BF). Multivariable linear mixed models were used to assess the association between serum 25(OH)D and body composition over the two-year period measured at 1 year interval. Linear mixed models (LMM) were used to determine the longitudinal association between lean mass and %BF (exposures) and BMD (outcome). Results: The 120 study participants average age was 40 years. Vitamin D deficiency and insufficiency increased from baseline (10.2% and 19.5%) to 11.5% and 37.5%, respectively, after two years. Serum 25(OH)D had no association with any BMD outcomes. Lean mass and %BF had comparable positive associations with total spine and left hip femoral neck (FN) BMD, however, lean mass proved as a stronger predictor. Serum 25(OH)D decreased significantly, however with a small effect size of 0.39 (P = 0.001), while total BMD, left hip FN BMD had significant small increases (effect size 0.03, P = 0.02 and 0.06, P = 0.0001 respectively), whereas total spine BMD did not change over the two years. Conclusion: Serum 25(OH)D was not associated with any BMD outcomes. Though lean mass and %BF had a comparable positive association with BMD, the former exhibited a stronger association with BMD.