Department of Pediatrics, Child Growth and Development Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Community Medicine, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran.
Pediatrics Department, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Department of Epidemiology, Chronic Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
Department of Environmental Health, Environment Research Center, Research Institute for Primordial Prevention of Non-Communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran.
Background: Sunlight is the main source of vitamin D; therefore, environmental factors might have an important role in the high prevalence of hypovitaminosis D in children. This study aimed to assess the vitamin D status according to the climate of the living area in a nationally representative sample of Iranian adolescents.
Material and Methods: This nationwide cross-sectional survey was performed among a representative sample of 1,095adolescents aged 10-18 years, selected by multistage cluster sampling method from 27 provinces of Iran. Serum 25-hydroxyvitamin D [25(OH) D] concentrations was compared in inhabitants of humid-rainy, cold-mountainous, and sunny regions.
Results: Vitamin D deficiency was documented in 40% of participants including 40.70% of boys and 39.30% of girls. We found significant difference in 25(OH) D concentrations among participants living in the three different climates of the living area (P<0.05). The median inter-quartile range (IQR) level for 25(OH)D was lower in humid-rainy climate: 11.40 (18.64). Hypovitaminosis D was more frequent in humid-rainy climate (42.30%), compared to other climates; this difference was more prominent in urban areas (P<0.05). Boys living in various climates had significantly different levels of 25(OH) D(P<0.05), however this figure was not significantly different for girls (P>0.05). The highest frequency of hypovitaminosis D (45.2%) was documented among boys living in humid-rainy regions.
Conclusion: The high prevalence of hypovitaminosis D, notably among inhabitants of humid-rainy region underscores the necessity of implementing national preventive strategies. This is of great importance especially in regions with lower exposure to sunlight.