Aim: To determine the prevalence of vitamin D deficiency and associated factors among students of age 13-18 years.
Design: Community-based cross sectional survey.
Setting: Two schools were selected using multistage sampling techniques.
Sampling: Cluster sampling of all enrolled students (550 students).
Outcome measures: Serum levels of 25-hydroxyvitamin D (25 OHD), parathyroid hormone and calcium. Data was collected about nutritional intake, physical activity and lifestyle variables that are potential risk factors for hypovitaminosis D.
Results: Hypovitaminosis D prevalence was 23.8%, of which 5.3% was deficiency and 18.5% insufficiency. Serum 25 OHD levels inversely correlated with parathyroid hormone levels (r=-0.206, P= 0.00). Low calcium and ionized calcium levels were 40.6% and 45.9%, respectively, and significantly correlated with vitamin D levels. Female students have significantly higher levels of hypovitaminosis D compared to males (29.3% to 15.0%, respectively) and the level of vitamin D significantly improved with increased age. Exposure to sun had a significant effect on vitamin D levels, and physical activity, soft drink consumption and smoking did not. Multinomial regression analysis revealed that age, sun exposure and Ca level were the only significant independent predictors of hypovitaminosis D among the studied group.
Conclusion: Our findings revealed that hypovitaminosis D is a prevalent health problem in adolescents, especially girls, who were at higher risk, and increased age and sun exposure improved vitamin D status among the studied group. There is therefore a need to consider vitamin D supplementation for school children together with increased awareness through a health education program.
Keywords: adolescents; calcium; ionized calcium; parathormone; vitamin D deficiency.