Serum 25-hydroxyvitamin D concentration among users of a referral outpatient unit for vascular diseases and associated factors.

Objective: Assess serum 25-hydroxyvitamin D (25OHD) concentration and associated factors among users of a referral outpatient unit for vascular diseases in Southern Brazil.

Design: Cross-sectional study conducted for almost one year, from March 2016 to January 2017. The serum vitamin D level was determined biochemically and classified as: sufficient (>50 nmol/L), insufficient (30-50 nmol/L) and deficient (<30 nmol/L). Associations were tested through multiple linear regression.

Setting: At a reference outpatient clinic specialized in vascular diseases located in a southern Brazilian medium-sized city (latitude 29°S).

Subjects: Consecutive sample of 133 individuals of both sexes, aged at least 40 years.

Results: The mean serum 25OHD concentration was 54.9 ± 25.9 nmol/L (57.7 ± 27.9 nmol/L for men; 52.2 ± 24.2 nmol/L for women, p = 0.267). A total of 12.8% of the participants had vitamin D deficiency and 32.3% had insufficiency. Regarding the total sample, variables associated to the serum 25OHD concentration were: age (β = -0.55; CI95% -0.95; -0.17), sun exposure (β = 1.22; CI95% 0.32; 2.10) and vitamin D intake (β = 7.29; CI95% 2.10; 12.48). Among men, a significant association was observed for age (β = -0.82; CI95% -1.47; -0.17, p = 0.015) and borderline for sun exposure (β = 1.22; CI95% 0.32; 2.10, p = 0.053). Among women, only vitamin D intake was significantly associated with serum concentration of this vitamin (β = 8.74; CI95% 1.32; 16.17, p = 0.022).

Conclusion: Although the mean 25OHD concentration was greater than 50 nmol/L, about 45% of this consecutive sample presented poor vitamin D nutritional status. Unadjusted for seasonality, factors associated with serum 25OHD concentration were age and sun exposure among men and vitamin D intake among women.