Prevalence and cut-off point of vitamin D deficiency among secondary students of Arak, Iran in 2010

INTRODUCTION: Vitamin D has a basic role in bone growth and metabolism and has been noticed for its important role in many diseases, such as diabetes, depression, hypertension, and cardiovascular disease. Regarding some studies, detection of vitamin D deficiency in different places has important implication for health. This study determined prevalence of vitamin D deficiency in Arak, a centrally located city in Iran. MATERIALS AND METHODS: Based upon a cross-sectional study in 2010, 420 students 10--16 years old including 220 girls and 200 boys, studied at Arak secondary schools, were selected by a multistage sampling. The level of 25 (OH) D and PTH (parathormone) was measured and also the prevalence of vitamin D deficiency in different intensities was evaluated and compared between girls and boys by the Student t-test. Vitamin D deficiency for the students was categorized into three intensities based on three levels of 25 (OH) D: mild deficiency - 15 ≤ 25 (OH) D < 20 ng/ml, moderate deficiency -- 8 ≤ 25 (OH) < 15 ng/ml, severe deficiency - 25 (OH) <8 ng/ml. The relationship between the 25 (OH) D and PTH was assessed by Scatter chart to define cut-off points for vitamin D deficiency. RESULTS: Based on 25 (OH) D < 20 ng/ml, 84% of the students had vitamin D deficiency including 60.7% mild, 22.4% moderate, and 0.7% severe. Three local cut-off points including 13, 21, and 33 ng/ml were defined in the Scatter chart. The results showed that the deficiency of vitamin D in girls is much more than that in boys (P = 0.05). CONCLUSION: The high prevalence of vitamin D deficiency could be probably a result of different etiologies. We recommended that people should be encouraged to take vitamin D and calcium supplements and also they should have more exposure to the sunlight.