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 chisquare 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.