Low Serum 25-Hydroxyvitamin D Is Associated with Increased Risk of the Development of the Metabolic Syndrome at Five Years: Results from a National, Population-Based Prospective Study (The Australian Diabetes, Obesity and Lifestyle Study: AusDiab)

Context: Serum 25-hydroxyvitamin D [25(OH) D] concentration has been inversely associated with the prevalence of metabolic syndrome (MetS), but the relationship between 25(OH) D and incident MetS remains unclear. Objective: We evaluated the prospective association between 25(OH) D, MetS, and its components in a large population-based cohort of adults aged 25 yr or older. Design: We used baseline (1999-2000) and 5-yr follow-up data of the Australian Diabetes, Obesity, and Lifestyle Study (AusDiab). Participants: Of the 11,247 adults evaluated at baseline, 6,537 returned for follow-up. We studied those without MetSat baseline and with complete data (n = 4164; mean age 50 yr; 58% women; 92% Europids). Outcome Measures: We report the associations between baseline 25(OH) D and 5-yr Met S incidence and its components, adjusted for age, sex, ethnicity, season, latitude, smoking, family history of type 2 diabetes, physical activity, education, kidney function, waist circumference (WC), and baseline MetS components. Results: A total of 528 incident cases (12.7%) of MetS developed over 5 yr. Compared with those in the highest quintile of 25(OH)D (= 34 ng/ml), MetS risk was significantly higher in people with 25(OH)D in the first (= 18 ng/ml) and second (18-23 ng/ ml) quintiles;odds ratio (95% confidence interval) = 1.41 (1.02-1.95) and 1.74 (1.28-2.37), respectively. Serum 25(OH) D was inversely associated with 5-yr WC(P = 0.001), triglycerides (P = 0.01), fasting glucose (P = 0.01), and homeostasis model assessment for insulin resistance (P = 0.001) but not with 2-h plasma glucose (P = 0.29), high-density lipoprotein cholesterol (P = 0.70), or blood pressure (P = 0.46). Conclusions: In Australian adults, lower 25(OH) D concentrations were associated with increased MetS risk and higher WC, serum triglyceride, fasting glucose, and insulin resistance at 5 yr. Vitamin D supplementation studies are required to establish whether the link between vitamin D deficiency and MetS is causal. (J Clin Endocrinol Metab 97: 1953-1961, 2012)