Vertebral fracture prevalence in black and white South African women.

Abstract

Black women are generally regarded as being less prone to the development of osteoporosis. This study reports a similar prevalence of morphometric vertebral fractures in black (9.1 %) and white (5.0 %) South African women. Clinical risk factors and bone strength parameters contributed differently to fracture risk in the two ethnic cohorts. Vertebral fracture represents one of the most common osteoporotic fractures and is a significant cause of morbidity and mortality. Little is known regarding the prevalence of vertebral fractures on the African continent. We therefore prospectively examined the prevalence of vertebral fracture on radiographs of the thoraco-lumbar spine in otherwise healthy community-dwelling older black and white South African women. Radiographs of the spine (T4-L5) were obtained randomly in 189 women (47 % black), aged 40 years or older, for the analysis of vertebral fracture. Radiographs were evaluated by a single radiologist, blinded to clinical data, using Genant's semi-quantitative method. Clinical risk factors for osteoporosis, risk factors for falls (fall history, quadriceps strength, lateral sway and reaction time), areal and volumetric bone mineral density of the spine and hip, calcaneal ultrasonography (QUS) and vertebral macro-geometry were assessed in the two ethnic groups and the association with prevalent vertebral fractures examined. Vertebral fracture prevalence in older South African black and white women was similar (9.1 % in black and 5.0 % in white women). In black women, lower body weight and lower areal and volumetric bone mineral density (BMD) at all sites could serve as markers of increased fracture risk. Older age, physical inactivity, lower muscle strength and lower femoral BMD were associated with vertebral fracture risk in whites. Our findings are noteworthy and the first attempt to compare vertebral fracture risk in women of different ethnicities on the African continent. A similar vertebral fracture risk between black and white women in South Africa must be considered at present to ensure appropriate evaluation in all subjects who present with clinical risk factors for osteoporosis, regardless of ethnicity.