Saliba Walid, Barnett-Griness Ofra, Rennert Gad
Department of Community Medicine and Epidemiology, Carmel Medical Center, Clalit Health Services, and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel,
Calcif Tissue Int. 2014 Sep;95(3):222-8. doi: 10.1007/s00223-014-9885-0. Epub 2014 Jun 24.
Sequestration of vitamin D in adipose tissue is the main cause of the lower serum 25(OH)D levels in obese subjects. However, it remains unknown whether the adipose tissue stores of vitamin D are readily mobilized for meeting body needs. We aimed to examine whether the association between serum 25(OH)D and all-cause mortality differs by body weight. Using the computerized database of the largest health care provider in Israel, we identified a cohort of subjects ≥20-years old with serum 25(OH)D levels measured between January 2008 and December 2009. Mortality was ascertained through April-2013. Cox regression with restricted cubic-spline function was used to assess the association between serum 25(OH)D and mortality. Median follow-up was 48 months (IQR 43-53 months); 12,337 of 175,781 participants (7.0 %) died. The association between 25(OH)D and mortality was not linear (P < 0.001), and differed between BMI categories (P = 0.019). The lowest adjusted risk for mortality was observed at serum 25(OH)D levels of 73.0, 68.0, and 66.5 nmol/L among subjects with BMI <25, 25-29.9, and ≥30 kg/m(2), respectively. Compared to reference level of 75 nmol/L, increased adjusted HR as evident by 95 % confidence interval lower bound >1.0 was observed at serum 25(OH)D levels less than; 61.0, 48.0, and 40.0 nmol/L among subjects with BMI <25, 25-29.9, and ≥30 kg/m(2), respectively. Serum 25(OH)D levels associated with increased all-cause mortality were inversely related to BMI. However, this observational cohort study may still suffer from residual confounding; therefore, cause and effect relationship cannot be established from this study.
维生素D在脂肪组织中的隔离是肥胖受试者血清25(OH)D水平较低的主要原因。然而，维生素D在脂肪组织中的储存是否能轻易被调动以满足身体需求仍不清楚。我们旨在研究血清25(OH)D与全因死亡率之间的关联是否因体重而异。利用以色列最大医疗服务提供商的计算机化数据库，我们确定了一组年龄≥20岁、在2008年1月至2009年12月期间测量过血清25(OH)D水平的受试者。死亡率随访至2013年4月。使用带有受限立方样条函数的Cox回归来评估血清25(OH)D与死亡率之间的关联。中位随访时间为48个月（四分位间距43 - 53个月）；175,781名参与者中有12,337人（7.0%）死亡。25(OH)D与死亡率之间的关联不是线性的（P < 0.001），且在不同BMI类别之间存在差异（P = 0.019）。在BMI<25、25 - 29.9和≥30 kg/m²的受试者中，血清25(OH)D水平分别为73.0、68.0和66.5 nmol/L时，观察到的调整后死亡率风险最低。与75 nmol/L的参考水平相比，在BMI<25、25 - 29.9和≥30 kg/m²的受试者中，血清25(OH)D水平分别低于61.0、48.0和40.0 nmol/L时，观察到调整后HR增加，95%置信区间下限>1.0。与全因死亡率增加相关的血清25(OH)D水平与BMI呈负相关。然而，这项观察性队列研究可能仍存在残余混杂因素；因此，本研究无法确立因果关系。
