Seasonal Variation of Vitamin D via Several Parameters in Adolescents

INTRODUCTION: Vitamin D in adolescents revealed that subclinical vitamin D deficiency is continuously increasing worldwide. The aim of the study was to investigate the prevalence of vitamin D and subclinical vitamin D deficiency and risk factors among adolescents in summer and winter seasons in Izmir.
METHODS: The medical records of 90 adolescents were reviewed regarding D vitamin status in summer and winter seasons. Blood samples were obtained from 90 adolescents at the end of the summer and end of the winter. Samples assessed for calcium (Ca++), phosphorus (P), magnesium (Mg), parathyriod hormone (PTH), alkaline phosphatase (ALP) and 25 hydroxyvitamin D (25 (OH) D) concentration. The subjects were divided into two groups; first group was the patients who were assessed vitamin D levels and the other laboratory measurements at the end of the winter (n=46), second group was the patients who were assessed same laboratory features at the end of the summer (n=44). The two groups were compared in terms of demographic, clinical and laboratory characteristics.
RESULTS: Among the 90 patients enrolled in the study, 41 (45.5%) were males and 49 (54.5%) were females. The median age was 11±4 years. Vitamin D deficiency percentages of the study group for the end of the winter period were 60.8% and for the end of the summer period was 6.8% but not statistically different. Vitamin D insufficiency percentages of the winter group was higher than the summer group (93.2% vs 39.2%, p>0.05). There were no differences between the groups in terms of laboratory findings including calsium, magnesium and the other bone parameters.
DISCUSSION AND CONCLUSION: Contrary to the expected, we did not detect a seasonal difference in vitamin D levels in adolescents. Although laboratory findings was not found to be statistically significant in vitamin D levels, we can state that the level of vitamin D in winter seaseon might be lower than summer season. Therefore, it should be keep in mind that vitamin D insufficiency is frequent at the enf of winter season and should be considered seasonal differences in adolescent population during the measurement.