Prevalence of vitamin D deficiency and insufficiency among schoolchildren in Greece: the role of sex, degree of urbanisation and seasonality

The current study was aiming to report the prevalence of suboptimal vitamin D status among schoolchildren in Greece and investigate the role of sex, urbanisation and seasonality on vitamin D status. A sample of 2386 schoolchildren (9-13 years old) from four distinct prefectures was examined. The prevalence of 25-hydroxyvitamin D (25(OH)D) concentration <30 and <50 nmol/l (vitamin D deficiency and insufficiency respectively) was 5.2 and 52.5 %, respectively. Girls had a higher prevalence of 25(OH)D <30 (7.2 v. 3.2 %) and 50 nmol/l (57.0 v. 48.0 %) than boys (P < 0.001). The highest prevalence rates of 25(OH)D < 30 and 50 nmol/l (9.1 and 73.1 %, respectively) were observed during spring (April to June), whereas the lowest (1.5 and 31.9 %, respectively) during autumn (October to December). The prevalence of 25(OH)D < 50 nmol/l was higher in urban/semi-urban than rural regions, particularly during spring months (74.6 v. 47.2 %; P < 0.001). Female sex, urban/semi-urban region of residence and spring months were found to increase the likelihood of vitamin D deficiency and insufficiency, with the highest OR observed for spring months (7.47; 95 % CI 3.23, 17.3 and 5.14; 95 % CI 3.84, 6.89 for 25(OH)D < 30 and 50 nmol/l respectively). In conclusion, despite the southerly latitude, the prevalence of low vitamin D status among primary schoolchildren in Greece is comparable to or exceeds the prevalence reported among children and adolescents on a European level. Sub-populations at highest risk are girls in urban/semi-urban areas during spring months, thus indicating the need for effective initiatives to support adequate vitamin D status in these population groups.