AIM The aims of this study were to investigate changes in vitamin D status during two years in adolescence, and whether lifestyle changes were associated with serum 25-hydroxyvitamin D (s-25(OH)D) at follow-up. METHODS Fit Futures is a longitudinal study at 69°N in Norway. Participants had their s-25(OH)D levels analysed in their first and third year of upper secondary school (median age 16 and 18 years), in Fit Futures 1 (FF1) and Fit Futures 2 (FF2), respectively. Self-reported lifestyle habits were registered through questionnaires. The association between lifestyle changes and s-25(OH)D levels at follow-up were calculated by regression analyses, controlling for baseline s-25(OH)D levels. RESULTS Longitudinal data were available for 309 girls and 280 boys. The proportion of adolescents with s-25(OH)D < 50 nmol/L were 73.7% in FF1 and 77.1% in FF2, while the proportion <30 nmol/L constituted 35.7% in FF1 and 40.9% in FF2. Of those with s-25(OH)D < 30 nmol/L (severe vitamin D deficiency) in FF1, 73.3% remained severely deficient in FF2. Among boys, an increase in ultraviolet (UV)-exposure was significantly associated with higher s-25(OH)D levels in FF2 [beta; CI (nmol/L)] [12.9; 9.1, 16.7]. In girls, decreased vitamin/mineral supplement intake was significantly associated with lower s-25(OH)D at FF2 [-6.7; -10.2, -3.1], while increased UV [10.8; 7.0, 14.7] and combined hormonal contraceptive (CHC) exposure [12.1; 6.0, 18.1] in FF2 was significantly associated with higher s-25(OH)D levels in FF2. CONCLUSION Severe vitamin D deficiency was prevalent throughout adolescence. Lifestyle changes may alter s-25(OH)D levels in this age group.

中文翻译：

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青春期维生素 D 状况以及生活方式改变的影响 - Fit Futures 研究的两年随访。

目的 本研究的目的是调查青春期两年期间维生素 D 状态的变化，以及随访时生活方式的变化是否与血清 25-羟基维生素 D (s-25(OH)D) 相关。方法 Fit Futures 是一项在挪威北纬 69°进行的纵向研究。参与者在高中一年级和三年级（中位年龄 16 岁和 18 岁）分别在 Fit Futures 1 (FF1) 和 Fit Futures 2 (FF2) 中分析了他们的 s-25(OH)D 水平。通过问卷调查记录自我报告的生活习惯。通过回归分析计算生活方式改变与随访时 s-25(OH)D 水平之间的关联，并控制基线 s-25(OH)D 水平。结果 可获得 309 名女孩和 280 名男孩的纵向数据。s-25(OH)D<50nmol/L的青少年比例在FF1中为73.7%，在FF2中为77.1%，而<30nmol/L的比例在FF1中为35.7%，在FF2中为40.9%。在 FF1 中 s-25(OH)D < 30 nmol/L（严重维生素 D 缺乏）的患者中，73.3% 的 FF2 仍严重缺乏。在男孩中，紫外线 (UV) 暴露的增加与 FF2 β 中较高的 s-25(OH)D 水平显着相关；CI（纳摩尔/升）][12.9；9.1、16.7]。在女孩中，维生素/矿物质补充剂摄入量减少与 FF2 时 s-25(OH)D 较低显着相关[-6.7；-10.2，-3.1]，同时增加紫外线[10.8；7.0, 14.7] 和联合激素避孕药 (CHC) 暴露 [12.1; 6.0, 18.1] FF2 与 FF2 中较高的 s-25(OH)D 水平显着相关。结论 严重的维生素 D 缺乏症在整个青春期都很普遍。生活方式的改变可能会改变该年龄段的 s-25(OH)D 水平。