Repository logo

Bone health in Gambian women: impact and implications of rural-to-urban migration and the nutrition transition



Change log



Urbanisation and the associated nutrition transition have been linked with the recent rise in osteoporotic fragility fracture incidence in many countries. Predictions indicate that hip fracture incidence will increase 6-fold in Africa and Asia by 2050, partially attributed to demographic transition and population ageing. Differences in areal bone mineral density (aBMD) between rural and urban locations indicate that urban regions of high-income countries (HIC) have lower aBMD and a higher incidence of hip fracture. The few studies conducted in low and middle-income countries (LMIC) provide inconsistent results; in contrast to HIC, most have found higher aBMD in urban populations.
To investigate the impact of migrating to an urban environment, detailed studies of bone phenotype and factors affecting bone health have been conducted in two groups of pre-menopausal Gambian women: urban migrant (n=58) and rural (n=81). Both groups spent their formative years in the same rural setting of Kiang West, urban women were known to have migrated to coastal districts, concentrated in Brikama and Kanifing, when aged ≥16 years. Bone phenotype (bone mineral content (BMC); bone area (BA); aBMD, and size-adjusted BMC (adjusted for height, weight and BA) of the whole-body, lumbar spine and hip) was measured by dual energy x-ray absorptiometry (DXA), with further characterisation by peripheral quantitative computed tomography (pQCT). Data were also collected on anthropometry, body composition, food and nutrient intakes, physical activity, socio-demographic characteristics, vitamin D status, and 24hr urinary mineral outputs (Na, K, P, and Ca).
Mean age and height of rural and urban migrant groups were not significantly different (p>0.05). Urban migrant women were significantly heavier (p<0.01). Significant differences in BMC and aBMD were found between groups at all skeletal sites, with urban women having higher BMC and aBMD; BA was not significantly different. The greatest difference in BMC was found at the lumbar spine (8.5% ± SE 3.0, p<0.01), a meaningful difference, equivalent to 0.76 of rural SD. T- Scores were also calculated using a young adult (white, female) reference population, mean T- scores were -1.03 and -0.22, for rural and urban groups respectively. After adjusting for size, differences in whole-body and hip BMC were mostly attenuated (p>0.05), but difference in spine BMC remained significant (6.2% ± SE 2.1, p<0.01). These results indicate that rural-to-urban migration is associated with higher BMC; BA and height were similar, and difference in body weight could not fully account for higher BMC at the lumbar spine. Calcium intakes were low in both groups, urban migrant 294mg/d (IQR: 235 to 385) and rural 305mg/d (IQR: 222 to 420). Urban women had significantly lower intakes of potassium, magnesium and dietary fibre (p<0.01), related to lower consumption of fruit, green leafy vegetables and groundnuts. 25-hydroxy vitamin D status was good in both groups, urban migrant 64.0 ± 14.2nmol/L and rural 68.3 ± 15.7nmol/L (M ± SD, p>0.05). Implications for bone health of the nutrition and demographic transition, principally future fracture risk and other non-communicable diseases require further research in LMICs.

ORIGINAL CONTRIBUTION TO KNOWLEDGE To my knowledge, this is the first study investigating the impact of rural-to-urban migration on bone health to be conducted in sub Saharan Africa. It is the first study of bone health and determinants of bone health in an urban population in The Gambia.





Goldberg, Dr Gail


Bone health, nutrition, transition, rural-to-urban migration, sub Saharan Africa, The Gambia, women, vitamin D, urbanisation, global health


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Medical Research Council