Predictors of change in the peripheral skeletons of older adults in rural Gambia.

Growing aging populations across Sub-Saharan Africa (SSA) will lead to increases in osteoporosis and other chronic musculoskeletal conditions, data are required to understand musculoskeletal aging in the region. No longitudinal studies to date describe changes in bone in SSA. Repeat measures were acquired from rural Gambians (n=322, 52.5% female) aged 40-92 (mean(SD) 60(12)) years. pQCT outcomes were total area (TotA), total (TotBMD) and trabecular vBMD (TrBMD) from the 4% distal radius and tibia. Height (cm), weight (kg) and BMI (kg/m2) were recorded. Muscle function was assessed by handgrip dynamometry (max grip, N/kg) and jumping mechanography (relative force (kN/kg) and max relative power (kW/kg)). Bone turnover markers (BTM), serum collagen type 1 cross-linked beta-C-telopeptide (CTX) and type 1 procollagen N-terminal (P1NP), were measured. Percentage annual change for pQCT outcomes was calculated. Univariate analysis was performed to explore if baseline age, BMI, BTMs, or muscle function predicted bone change. Models were repeated with a sex adjustment. Results are presented as beta (95% CI) where beta is the percentage change per year per unit of the independent variable. Mean(SD) time to follow up was 1.8(0.3) years. At all sites Tot and TrBMD decreased and TotA increased except tibia TotA. Baseline age was predictor of change in radius TotBMD (-0.06(-0.10,-0.02)) and TotA (0.07(0.01,0.10)), and tibia TrBMD (-0.04(-0.07,-0.01)). Greater baseline grip strength was associated with less decrease in tibia TotBMD (0.003(0.001,0.006)) and TrBMD (0.006 (0.002,0.009)). Similarly greater force was associated with less decrease in radius TotBMD (0.16(0.03,0.29)) and power with less decrease in tibia TrBMD (0.04(0.01,0.08)), and radius TotBMD (0.07(0.02,0.12)). Greater force and power were associated with less change in radius TotA (-0.17(-0.31,-0.02);-0.06(-0.11,-0.01)); whereas at the tibia greater power was associated with greater change in TotA (0.02(0.01,0.05)). B