Prevalence of vitamin D deficiency in older South Africans with and without hip fractures and the effects of age, body weight, ethnicity and functional status

Abstract

Background: Vitamin D plays an important role in many physiological and pathological processes, including bone metabolism. Vitamin D deficiency is common worldwide, but there are few data in older South Africans. Objectives: This study aimed to determine vitamin D status in older adults with and without hip fractures and the effect of demography, body mass index (BMI) and functional status on vitamin D levels. Methodology: In a secondary analysis, the association between 25(OH) vitamin D levels, obtained from 327 subjects (151 with fractures and 176 controls), and age, gender, ethnicity, BMI and functional status, was explored using Student's t-test, a chi-square test, regression analysis and ANOVA. Results: In the total cohort, vitamin D deficiency and insufficiency was present in 27% and 38%, respectively. While vitamin D levels decreased with age, this was not significant (p=0.082). There was a significant association between vitamin D and BMI (p=0.023), the physical maintenance scale (p=0.002) and independent activities of daily living (p=0.001). Mean vitamin D levels in fracture subjects was significantly lower than controls (39.4 +/- 23.1 nmol/l vs. 50.1 +/- 23.3 nmol/l, p=0.00) and vitamin D deficiency and/or insufficiency was significantly more common in the fracture group compared with controls (75.5% vs. 56.8%, p=0.00). There was no association with gender or ethnicity. Conclusions: Vitamin D deficiency is common in this population, especially in those with hip fractures. Contrary to other studies, increasing BMI was associated with higher vitamin D levels. This suggests that poor health status as indicated by a low BMI and poorer functional status is associated with lower vitamin D levels. The high prevalence of vitamin D deficiency and/or insufficiency in the cohort strongly argues for universal vitamin D supplementation in older adults, especially those at risk for osteoporotic fractures.