Rural–urban differences in osteoporosis and sarcopenia prevalence among Gambian older adults: a pilot study

Rural-urban bone mineral density (BMD) differences are well-described in high-income countries, typically with higher BMD in rural areas. However, despite rapid urbanization and longevity across Africa, such data remains scarce. This study compares bone and muscle health in older adults living in rural and urban Gambia. Participants aged ≥55 years from rural (n=209) and urban communities (n=101) were measured with dual-energy X-ray absorptiometry (DXA: total hip (TH), femoral neck [FN], and lumbar spine [LS]) and peripheral quantitative computed tomography (pQCT: diaphyseal and epiphyseal radius and tibia). Outcomes were: DXA areal BMD (aBMD), bone mineral content (BMC), bone area (BA); pQCT total volumetric BMD (vBMD), trabecular vBMD, bone strength indices (BSIc), cross-sectional area (CSA), BMC, and cortical vBMD. Osteoporosis (NHANES III, T-score <-2.5) and sarcopenia (EWGSOP2 ALM and HGS) prevalence were computed. Linear regression was used to describe rural-urban differences in DXA and pQCT outcomes (i) unadjusted and (ii) age and fat mass index (FMI) adjusted. Osteoporosis at either FN or TH was more prevalent in urban men (20% vs rural 10%) and rural women (45% vs urban 31%). LS T-scores <-2.5 were more common in rural participants (M: 27% vs 14%; F:61% vs 35%). Sarcopenia was also higher in rural participants (M:30% vs. 18%; F:18% vs. 15%). Adjusted for age and FMI urban Gambians had lower BMC but greater BA at the FN and TH, while aBMD differed little. Urban men had lower adjusted tibial cortical vBMD but greater tibial diaphyseal and radial epiphyseal CSA. After adjustment urban women had greater radial CSA and estimated strength. Our findings highlight that osteoporosis and sarcopenia are highly prevalent in older Gambian adults, with differences in rural-urban prevalence influenced by sex. Given ongoing nutrition transition and urbanization across Africa, larger population-based studies are urgently required to better inform targeted prevention strategies and interventions.