Abstract
BackgroundLow levels of serum 25–hydroxy vitamin D (25(OH)D), have been associated with development of type 2 diabetes and cardiovascular disease (CVD); however there are limited data on serum 25(OH)D in Indigenous Australians, a population at high risk for both diabetes and CVD. We aimed to assess levels of serum 25(OH)D in Aboriginal and Torres Strait Islander Australians and to explore relationships between 25(OH)D and cardio-metabolic risk factors and diabetes.Methods592 Aboriginal and/or Torres Strait Islander Australian participants of The eGFR (estimated glomerular filtration rate) Study, a cross-sectional analysis of a cohort study performed in 2007–2011, from urban and remote centres within communities, primary care and tertiary hospitals across Northern Territory, Far North Queensland and Western Australia. Assessment of serum 25(OH)D, cardio-metabolic risk factors (central obesity, diabetes, hypertension, history of cardiovascular disease, current smoker, low HDL-cholesterol), and diabetes (by history or HbA1c ≥6.5%) was performed. Associations were explored between 25(OH)D and outcome measures of diabetes and number of cardio-metabolic risk factors.ResultsThe median (IQR) serum 25(OH)D was 60 (45–77) nmol/L, 31% had 25(OH)D <50 nmol/L. For participants with 25(OH)D < 50 vs ≥50 nmol/L, cardio-metabolic risk profile differed for: diabetes (54%, 36% p < 0.001), past history of cardiovascular disease (16%, 9%, p = 0.014), waist-hip ratio (0.98, 0.92, p < 0.001), urine albumin-creatinine ratio (2.7, 1.5 mg/mmol, p < 0.001). The OR (95% CI) for diabetes was 2.02 (1.03 – 3.95) for people in the lowest vs highest tertiles of 25(OH)D (<53 vs >72 nmol/L, respectively) after adjusting for known cardio-metabolic risk factors.ConclusionThe percentage of 25(OH)D levels <50 nmol/L was high among Aboriginal and Torres Strait Islander Australians from Northern and Central Australia. Low 25(OH)D level was associated with adverse cardio-metabolic risk profile and was independently associated with diabetes. These findings require exploration in longitudinal studies.
Highlights
Low levels of serum 25–hydroxy vitamin D (25(OH)D), have been associated with development of type 2 diabetes and cardiovascular disease (CVD); there are limited data on serum 25(OH)D in Indigenous Australians, a population at high risk for both diabetes and CVD
The major contributor to the significantly reduced life expectancy of Indigenous Australians, compared to the general Australian population is the overwhelming burden of chronic diseases, such as ischaemic heart disease, diabetes and chronic kidney disease [1]
The Australian Diabetes, Obesity and Lifestyle (AusDiab) study reported that 31% of adults in Australia had serum 25 (OH)D levels less than 50 nmol/L, with a higher prevalence during winter–spring and in people residing in southern states [6]
Summary
Low levels of serum 25–hydroxy vitamin D (25(OH)D), have been associated with development of type 2 diabetes and cardiovascular disease (CVD); there are limited data on serum 25(OH)D in Indigenous Australians, a population at high risk for both diabetes and CVD. Low levels of serum 25–hydroxy vitamin D (25(OH)D), the best marker for vitamin D status, have been associated with development of the metabolic syndrome [2], diabetes [3,4] and cardiovascular disease [5] in many parts of the world, but there are limited data on serum 25(OH)D levels in the high risk Indigenous Australian population. Small studies from the tropical region of Far North Queensland have reported a low prevalence of vitamin D deficiency in a healthy obstetric population (0%) [9] and in free-living adults (6.2%) [10]. Large population-based studies on vitamin D status are lacking in tropical Australia
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