vicky3

作者：Laurie Barclay, MD  
出處：WebMD醫學新聞

　　October 1, 2009 — 根據10月2日線上第一版BMJ期刊中的統合分析報告，高劑量維他命D補充品可以減少年長者的跌倒風險。
　　
　　瑞士蘇黎士大學的H.A. Bischoff-Ferrari醫師等人寫道，在有維他命D缺乏風險之年長者的許多試驗中，維他命D補充品改善了強度、功能與平衡，且與劑量相關。更重要的是，這些幫助可以減少跌倒。不過，整體而言，以維他命D預防跌倒的結果互異；例如，許多維他命D試驗的結果不顯著。
　　
　　此一統合分析的目標是評估各種類型的維他命D、有無含鈣之補充品對於預防年長者跌倒的效果。回顧者在Medline、Cochrane控制試驗登記中心、BIOSIS、與Embase搜尋至2008年8月的相關文章，他們從書目與摘要尋找其他研究，並且由臨床專家提供諮商。回顧者聯絡適合的文章的作者，以獲得更多資料。
　　
　　納入規範是雙盲隨機控制試驗，納入的研究對象平均年紀為65歲，有充分的有關跌倒的評估。這些納入試驗的研究對象，被給予一定劑量的口服維他命D(維他命D3 [cholecalciferol]或維他命D2 [ergocalciferol])或一種維他命D活性物(1α-hydroxyvitamin D3 [1α-hydroxycalciferol]或1,25-dihydroxyvitamin D3 [1,25-dihydroxycholecalciferol])。
　　
　　有八個隨機控制試驗的維他命D補充品符合納入規範，總共有2,426名參與者。研究者觀察這些試驗之維他命D劑量的異質性(700 - 1000 IU/天vs 200 - 600 IU/天; P = .02)，以及達到的25-hydroxyvitamin D3濃度(25 [OH]D濃度：< 60 nmol/L vs ≧60 nmol/L；P = .005)。
　　
　　在七篇試驗、1,921名研究對象中，使用高劑量維他命D補充品與各種跌倒風險減少19%有關(彙整之相對風險(RR)為0.81；95%信心區間[CI]為0.71 - 0.92)。達到的血清25 (OH)D濃度至少有60 nmol/L，則與減少23%跌倒風險有關(彙整之RR為0.77；95% CI為0.65 - 0.90)。
　　
　　相對的，有兩篇試驗、505名研究對象顯示，使用低劑量維他命D補充品的跌倒風險降低並不值得一提(彙整之RR為1.10；95% CI為0.89 - 1.35)。而且，達到的血清25(OH)D濃度少於60 nmol/L對於跌倒風險有顯著影響(彙整之RR為1.35；95% CI為0.98 - 1.84)。在兩個符合納入規範的隨機控制試驗 (n = 624人)中，維他命D活性物與降低22%跌倒風險有關(彙整之RR為0.78；95% CI為0.64 - 0.94)。
　　
　　研究作者寫道，維他命D補充品每天劑量700-1000 IU可降低年長者的跌倒風險達19%，且維他命D活性物有類似的效果。維他命D補充品每天劑量低於700 IU或血清25-hydroxyvitamin D 濃度低於60 nmol/L，可能無法降低年長者的跌倒風險。
　　
　　研究限制包括可能有發表偏見，各試驗的差異大於預期。研究作者結論表示，每天劑量700-1000 IU的維他命D補充品，可以減少跌倒達19%，而維他命D3甚至可減少跌倒達26%。此效果與額外的鈣補充無關，在治療2-5個月內有顯著結果，且治療12個月後持續。對於年長者的跌倒預防，維他命D活性物並未優於700-1000 IU的維他命D補充品。
　　
　　瑞士國家基金會教授資金、Velux基金會、Baugarten基金會、Vontobel基金會、以及Robert Bosch基金會的研究獎金支持本研究。回顧作者之一接受國家老化研究中心資助。其他回顧作者宣告沒有相關財務關係。
　　
　　BMJ.線上發表於2009年10月2日。

High-Dose Vitamin D Supplement May Reduce Risk of Falling Among Older People

By Laurie Barclay, MD
Medscape Medical News

October 1, 2009 — High-dose vitamin D supplementation may reduce the risk of falling among older people, according to the results of a meta-analysis reported in the October 2 Online First issue of the BMJ.

"In several trials of older individuals at risk for vitamin D deficiency, vitamin D supplementation improved strength, function, and balance in a dose-related pattern," write H.A. Bischoff-Ferrari, MD, MPH, from the University of Zurich in Zurich, Switzerland, and colleagues. "Most importantly, these benefits translated into a reduction in falls. Overall, however, results have been mixed for fall prevention with vitamin D; for example, several trials of vitamin D have had non-significant results."

The goal of this meta-analysis was to evaluate the efficacy of supplemental and active forms of vitamin D with or without calcium in preventing falls among older individuals. The reviewers searched for relevant articles in Medline, the Cochrane central register of controlled trials, BIOSIS, and Embase up to August 2008, and they found additional studies from bibliographies and abstracts and by consulting clinical experts. When indicated, the reviewers contacted study authors for additional data.

Inclusion criteria were double-blind, randomized controlled trials enrolling groups of individuals of mean age 65 years or older, with sufficiently specified fall assessment. Participants in included trials were given a defined oral dose of supplemental vitamin D (vitamin D3 [cholecalciferol] or vitamin D2 [ergocalciferol]) or an active form of vitamin D (1α-hydroxyvitamin D3 [1α-hydroxycalciferol] or 1,25-dihydroxyvitamin D3 [1,25-dihydroxycholecalciferol]).

There were 8 randomized controlled trials of supplemental vitamin D that met inclusion criteria, enrolling a total of 2426 participants. The investigators observed heterogeneity among trials for dose of vitamin D (700 - 1000 IU/day vs 200 - 600 IU/day; P = .02) and for achieved 25-hydroxyvitamin D3 concentration (25 [OH)D concentration: < 60 nmol/L vs ? 60 nmol/L; P = .005).

In 7 trials enrolling a total of 1921 subjects, use of high-dose supplemental vitamin D was associated with a 19% reduction in fall risk (pooled relative risk (RR), 0.81; 95% confidence interval [CI], 0.71 - 0.92). Achieved serum 25 (OH)D concentrations of at least 60 nmol/L were associated with a 23% reduction in fall risk (pooled RR, 0.77; 95% CI, 0.65 - 0.90).

In contrast, 2 trials enrolling a total of 505 subjects showed that use of low-dose supplemental vitamin D was not associated with a notable reduction in fall risk (pooled RR, 1.10; 95% CI, 0.89 - 1.35). Also, achieved serum 25 [OH)D concentrations of less than 60 nmol/L appeared to affect fall risk significantly (pooled RR, 1.35; 95% CI, 0.98 - 1.84). In 2 randomized controlled trials (n = 624) meeting inclusion criteria, active forms of vitamin D were associated with a 22% reduction in fall risk (pooled RR, 0.78; 95% CI, 0.64 - 0.94).

"Supplemental vitamin D in a dose of 700-1000 IU a day reduced the risk of falling among older individuals by 19% and to a similar degree as active forms of vitamin D," the study authors write. "Doses of supplemental vitamin D of less than 700 IU or serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l may not reduce the risk of falling among older individuals."

Limitations of this study include potential publication bias and larger-than-expected variation between trials. "Doses of 700 IU to 1000 IU supplemental vitamin D a day could reduce falls by 19% or by up to 26% with vitamin D3," the study authors conclude. "This benefit may not depend on additional calcium supplementation, was significant within 2-5 months of treatment, and extended beyond 12 months of treatment....Active forms of vitamin D do not appear to be more effective than 700-1000 IU of supplemental vitamin D for fall prevention in older persons."

A Swiss National Foundations Professorship grant, the Velux Foundation, the Baugarten Foundation, the Vontobel Foundation, and a fellowship from the Robert Bosch Foundation supported this study. One of the review authors was funded by the National Institute on Aging. The other review authors have disclosed no relevant financial relationships.

BMJ. Published online October 2, 2009.