Vitamin D deficiency and secondary hyperparathyroidism: clinical and biochemical associations in older non-institutionalised Southern Tasmanians

Aim : To determine the prevalence and associations of vitamin D (25-OHD) deficiency in a sample of older Tasmanian subjects.
Methods : A cross-sectional survey of: 109 patients with a mean age of 79 years (range 60–101 years) consecutively admitted to a short stay geriatric rehabilitation ward; 52 community dwelling subjects with a mean age of 75 years (range 64–88 years). Subjects answered a questionnaire, had anthropometric measurements and underwent venepuncture.
Results : The main outcome measure was 25 hydroxy vitamin D (25-OHD) level with deficiency defined as < 28 nmol/L. Vitamin D deficiency was found in 67% and secondary hyperparathyroidism in 49% of the hospitalised group. Vitamin D deficiency was also found in 17% of the community group, in particular one in three residents of Independent Living Units was deficient. Subjects who were deficient were older (80 years vs 76 years [ p <0.001]), had lower body mass index (23.7 kg/m² vs 25.9 kg/m² [ p <0.001]) and had a lower serum albumin (35 gm/L vs 39 gm/L [ p <0.001]). Deficient subjects had poorer physical functional status ( p =0.02) and lower activity levels ( p <0.001) and reported less habitual sun exposure ( p <0.001). Biochemical measures such as parathyroid hormone, alkaline phosphatase and calcium were weakly predictive of vitamin D levels. By stepwise multiple regression analysis, the only significant predictors of vitamin D levels were the Frenchay Activity Index, albumin and calcium.
Conclusion : Vitamin D deficiency and secondary hyperparathyroidism is common in community living older people who are hospitalised in Southern Tasmania and is associated with increasing age, poor physical function and activity and low reported sun exposure.