据5月12日刊JAMA上的一则研究披露，与服用安慰剂的妇女相比，那些年龄70岁或以上的每年接受单一高剂量维生素D的妇女其发生跌倒和骨折的风险要更高。
有关研究维生素D3补充剂对跌倒和骨折的影响的研究结果一直相互矛盾，有些荟萃分析表明维生素D可降低骨折的风险，而另外一些研究则得出维生素D补充剂无效或是可能增加骨折风险的结论。根据文章的背景资料，对那些试图通过维生素D来改变跌倒或骨折风险的个人来说，坚持每日服用维生素D补充剂常常无法做到。
University of Melbourne, Geelong, Australia的Kerrie M. Sanders, Ph.D.及其同僚开展了一项研究，旨在检查每年口服一次的高剂量的维生素D3（500,000 IU）是否可减少老年妇女发生跌倒和骨折的危险。维生素D3作为单一高剂量来服用是为了解决人们不易坚持服药的问题以及它可作为一个能轻松转变为临床实践的实用性治疗。这项研究中包括了2256名居住在社区中的年龄在70岁或以上的妇女，她们被认为是发生骨折的高风险人群。这些人是在2003年6月至2005年6月间加入该项研究并被随机分配至接受500,000 IU维生素D3或安慰剂小组的，她们在每年的秋季至冬季之间服药，时间为3-5年。该研究在2008年结束。
在该研究期间，受试者中总共发生了5404起跌倒事件，在服用维生素D的小组中，有837名妇女中有74%至少发生过一次跌倒，而在安慰剂组中，769名妇女中有68%至少发生过一次跌倒。分析表明，在每年服用一次高剂量的维生素D的小组中的妇女发生跌倒的次数要多出15%。在服用维生素D小组的妇女中发生了171起骨折事件，而在安慰剂组中则发生了135起骨折事件：在维生素D组中者发生的骨折数要高出26%，而且她们在服药之后的头3个月中发生跌倒的事件也要高出31%。
推荐原文出处：
JAMA. 2010;303(18):1815-1822.
Annual High-Dose Oral Vitamin D and Falls and Fractures in Older Women
Kerrie M. Sanders, PhD; Amanda L. Stuart, BappSc; Elizabeth J. Williamson, MA, PhD; Julie A. Simpson, PhD; Mark A. Kotowicz, MBBS, FRACP; Doris Young, MD, MBBS, FRACGP; Geoffrey C. Nicholson, PhD, FRACP
Context Improving vitamin D status may be an important modifiable risk factor to reduce falls and fractures; however, adherence to daily supplementation is typically poor.
Objective To determine whether a single annual dose of 500 000 IU of cholecalciferol administered orally to older women in autumn or winter would improve adherence and reduce the risk of falls and fracture.
Design, Setting, and Participants A double-blind, placebo-controlled trial of 2256 community-dwelling women, aged 70 years or older, considered to be at high risk of fracture were recruited from June 2003 to June 2005 and were randomly assigned to receive cholecalciferol or placebo each autumn to winter for 3 to 5 years. The study concluded in 2008.
Intervention 500 000 IU of cholecalciferol or placebo.
Main Outcome Measures Falls and fractures were ascertained using monthly calendars; details were confirmed by telephone interview. Fractures were radiologically confirmed. In a substudy, 137 randomly selected participants underwent serial blood sampling for 25-hydroxycholecalciferol and parathyroid hormone levels.
Results Women in the cholecalciferol (vitamin D) group had 171 fractures vs 135 in the placebo group; 837 women in the vitamin D group fell 2892 times (rate, 83.4 per 100 person-years) while 769 women in the placebo group fell 2512 times (rate, 72.7 per 100 person-years; incidence rate ratio [RR], 1.15; 95% confidence interval [CI], 1.02-1.30; P = .03). The incidence RR for fracture in the vitamin D group was 1.26 (95% CI, 1.00-1.59; P = .047) vs the placebo group (rates per 100 person-years, 4.9 vitamin D vs 3.9 placebo). A temporal pattern was observed in a post hoc analysis of falls. The incidence RR of falling in the vitamin D group vs the placebo group was 1.31 in the first 3 months after dosing and 1.13 during the following 9 months (test for homogeneity; P = .02). In the substudy, the median baseline serum 25-hydroxycholecalciferol was 49 nmol/L. Less than 3% of the substudy participants had 25-hydroxycholecalciferol levels lower than 25 nmol/L. In the vitamin D group, 25-hydroxycholecalciferol levels increased at 1 month after dosing to approximately 120 nmol/L, were approximately 90 nmol/L at 3 months, and remained higher than the placebo group 12 months after dosing.
Conclusion Among older community-dwelling women, annual oral administration of high-dose cholecalciferol resulted in an increased risk of falls and fractures.
