Serum vitamin D levels, diabetes and cardio-metabolic risk factors in Aboriginal and Torres Strait Islander Australians

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.

Seasonality of hip fracture and vitamin D deficiency persists in a sub‐tropical climate

“…6 Deficiency of 25-OHD is common in darker-skin populations living in western countries, 18 including indigenous Australians. 19 Our observation that the prevalence of vitamin D deficiency among hip fracture patients fell significantly between 2009 and 2015 is likely due to improved recognition and treatment in the community, since clinically significant changes in the 25-OHD assay performance have not been observed. Factors other than 25-OHD deficiency are clearly involved in the seasonal variation in hip fracture in our cohort.…”

“…For most individuals 25‐OHD increases during summer but for some individuals it decreases due to sun avoidance . Deficiency of 25‐OHD is common in darker‐skin populations living in western countries, including indigenous Australians …”

Associations of Serum 25-Hydroxyvitamin D with Adiposity and At-Risk Lipid Profile Differ for Indigenous (Orang Asli) Male and Female Adults of Peninsular Malaysia

“…In addition, the prevalence of vitamin D deficiency (25 (OH)D concentration <50 nmol/L) in Orang Asli adults (1.4%) was much lower than other Malaysian adults (ranged from 12.2% to as high as 80.9%). Although the Orang Asli adults seemed to have better vitamin D status as compared to indigenous peoples residing in other countries [56][57][58], it should be noted that the comparison is limited as key characteristics such as latitude of residence may differ between groups. Living near to the equator allows Orang Asli adults, who usually spend more time outdoor, to receive more sunlight throughout the year and it may enhance the cutaneous synthesis of vitamin D.…”

Vitamin D-binding protein as it is understood in 2016: is it a critical key with which to help to solve the calcitriol conundrum?

“…[50][51][52][53] Those results are tabulated below. Further, between 2014 and 2015, three other scientifically acceptable Australian studies have independently assayed Australian indigenous patients' calcifediol on an immunoassay platform [54][55][56] and a further two with an MS/MS instrument. 57,58 Details are tabulated in the Table S3.…”