Influence of seasonal variation in 25-hydroxyvitamin D3 levels of adults with metabolic syndrome of the Brazil's region with high UV index.
Metabolic syndrome; vitamin D; exposure to sunlight; UV index.
This study aimed to evaluate the influence of the seasons on the status of 25 -hydroxyvitamin D3 (25OHD) in patients with metabolic syndrome (MS) attended at the Endocrinology Clinic of the University Hospital Onofre Lopes – HUOL of Federal University of Rio Grande do Norte-UFRN, Natal- Brazil. A cross-sectional study was conducted with 180 subjects adult and elderly aged 18-80 years, diagnosed with MS according to the NCEP-ATP III. The dependent variable was the status of 25OHD and as independent variables were age, sex, skin color, sunscreen use, phototype skin, sun exposure score, ultraviolet index (UVI), geographic location, seasonality, body mass index (BMI), waist-to-hip ratio (WHR), waist circumference (WC), serum total calcium, calcium and vitamin D from diet and parathormone (PTH). Association measures and correlation were established. Statiscal significance was assumed 5% (P < 0.05). These participants, 141 (78%) were women and 39 (22 %) were men, with a mean age of 50.11+12.26 years. The level of 25OHD was statiscal difference between winter and summer (P=0.017), with the status of 25OHD insufficient (25.89ng/mL+7.61) in winter and sufficient (31.81ng/mL+10.22) in summer. In the simple linear regression model, the status of 25OHD, showed significant association in summer (P=0.003), so that the variable season explained 4.24% of the variability 25OHD level. In the multiple regression model, the variables, sex, WHR, sun exposure score and the seasons, explained 10.4% of the variation of 25OHD status. The men showed status of 25OHD statistically higher when compared to women (difference= + 3.71ng/mL, 95% IC=0.43 to 7.00ng/mL, P=0.027). The increase in 1.0 unity of sun exposure score was statistically associated with increase 0.16 ng/mL in the status 25OHD. The season proved to be an independent predictor of 25OHD status. Comparisons between seasons, the 25OHD level was on average 5.59ng/mL higher in summer than in winter (95% CI=1.81 to 9.38 ng/mL, P=0.024).