Winter 25-hydroxyvitamin D levels in young urban adults are affected by smoking, body mass index and educational level.

Background/objectives: To study the relationship of winter 25-hydroxycholecalciferol (25-OHD) levels with age, education, place of residency, marital status and body mass index (BMI) as they may affect sun exposure, vitamin D synthesis and metabolism.

Subjects/methods: Subjects (1952) answered a structured questionnaire concerning education, marital status and smoking; and body weight/height, and parathyroid hormone and 25-OHD were measured.

Results: 25-OHD levels were higher in the males with elementary and secondary education compared with higher education (46.8±18.5 and 43.7±16 vs 39.9±15.3 nmol/l, P<0.01). Vitamin D deficiency was more prevalent (16.7%, (13.1-20.2) vs 10.8%, (8.4-13.2), P=0.08) and sufficiency was less prevalent (24.6% (20-29.2) vs 33.7%, (29.5-37.8), P=0.005) in those with higher than secondary education. No differences were found among the females. Male smokers had lower 25-OHD than nonsmokers (40.2±16.6 vs 43.6±15.7 nmol/l, P=0.004). Deficiency was more prevalent in the male smokers than nonsmokers with secondary and higher education (secondary 16.6%, (10.1-22.4) vs 8.2%, (5.1-11.3), P=0.006; higher 27.4%, (17.7-37.1) vs 13.2%, (9.0-17.5), P=0.003). 25-OHD was lower in the obese than in the normal-weight females (34.6±16.2 vs 38.2±17.8 nmol/l, analysis of variance, P=0.014), but not males. Marital status was not related to 25-OHD. Only in the urban residents, increasing BMI in the young females increased the risk for vitamin D deficiency by 1%, and smoking had an odds ratio of 1.99 (1.05-3.78) in the young and 2.5 (1.07-5.75) in the middle-aged males.

Conclusions: Smoking and higher education in the males and obesity in the females were factors for vitamin D deficiency among Bulgarian urban population.