Bone mass in Saudi women aged 20-40 years: the association with obesity and vitamin D deficiency

Abstract

This study describes that low bone density is prevalent in premenopausal Saudi women, especially women of normal weight and vitamin D deficiency. Although BMD is higher in obese young women, this may not be beneficial later in life in conjunction with persistent vitamin D deficiency.

Introduction: Not attaining peak bone mass is one crucial factor contributing to the risk of developing osteoporosis and suffering fractures in later life. The objectives of this study were to describe the normal range of bone mineral density (BMD) and bone mineral content (BMC) in premenopausal Saudi women in relation to obesity and vitamin D insufficiency.

Methods: A cross-sectional study involving 312 healthy Saudi women aged 20-40. All women were clinically examined. BMD (g/cm²) and BMC (g) assessed at total body (TB), femoral neck (FN) and lumbar spine (LS) were performed using dual-energy X-ray absorptiometry (DXA). Obesity was defined as BMI ≥ 30 kg/m² and vitamin D deficiency defined as 25(OH)D < 50 nmol/L.

Results: Almost half of the studied women were obese, and the majority (86.2%) were deficient in vitamin D. Mean BMD in TB 1.060 ± 0.091, FN 0.918 ± 0.153 and LS 1.118 ± 0.123 g/cm², while TB-BMC 2077 ± 272 g. When classified by BMI, the proportion with low bone density was 2-3 times higher among the normal weight compared to the obese women, p < 0.001. In the cohort overall, ~ 19% of these young premenopausal women had osteopenia or osteoporosis at the femoral neck, but 26% in normal weight, vitamin D deficient women.

Conclusion: This study shows low bone density in premenopausal Saudi women, particularly those with normal weight. While obesity appears to confer some protection against vitamin D deficiency at this age, this is assumed to change in later life.

Keywords: Bone mass; Bone mineral content; Bone mineral density; Obesity; Premenopausal women; Saudi women.