Vitamin D deficiency in Tasmania: a whole of life perspective

This study aims to describe the lifetime picture of vitamin D deficiency, as measured by serum 25(OH)D concentration, in Tasmania (latitude 43°S).

Five cross-sectional studies were used: a sample of primary schoolchildren (n = 201, aged 7-8 years), two samples of adolescents (sample 1: n = 374, aged 15-18 years; sample 2: n = 136, aged 16-19 years), a sample of young to middle-aged adults (n = 262, aged 19-59 years) and a sample of older adults (n = 1092, aged 50-80 years).

In winter/spring, approximately two-thirds of the adolescents and adults (young, middle-aged and older) had 25(OH)D levels ≤50 nmol/L, and around 10% had 25(OH)D levels ≤25 nmol/L. The prevalence of vitamin D deficiency was much lower for primary schoolchildren (11.5% < 50 nmol/L, 0.5% ≤ 25 nmol/L). In summer/autumn, approximately one-third of the adolescents and adults had 25(OH)D levels ≤50 nmol/L, and very few had 25(OH)D levels ≤25 nmol/L. For the adolescents and adults, even among those who reported the highest category of sun exposure, approximately 45% had 25(OH)D levels ≤50 nmol/L in winter/spring.

Vitamin D deficiency was uncommon among our sample of primary school children but increased substantially during the teenage years and seemed to remain high throughout the rest of life, suggesting that mild vitamin D deficiency is endemic in Tasmania apart from in the very young.