維他命D值低與黃斑部病變風險有關


  【24drs.com】根據線上發表於4月2日Maturitas期刊的一篇系統回顧與一篇統合分析,體內的25-hydroxyvitamin D (25OHD)濃度最低的成年人,發生老年性黃斑部病變(age-related macular degeneration,AMD)的風險最高。
  
  法國Angers大學醫院Cedric Annweiler博士等人寫道,這篇統合分析的結果,強化了維他命D缺乏和AMD之間有關聯的觀念,尤其是在該疾病的後期(P=0.002);因此,針對維他命D缺乏進行處置可能可以改善AMD的預後。
  
  研究者使用Medline搜尋2015年11月前的資料,在發現的243篇研究中,有11篇研究符合他們的篩選準則。準則是,有關於AMD診斷(至少一眼)與維他命D濃度等結果資料的觀察型或介入型研究。
  
  這些研究中,7篇是橫斷面研究、1篇是案例報告、1篇是案例控制研究、1篇是回溯縱向世代研究、1篇是不一致性的兄弟姐妹世代研究,樣本數介於65-17,045名研究對象;患有AMD的人數介於31 -1440人。研究者將AMD分類為整體、早期或後期,這些研究都是在2007年後發表。
  
  包含3篇研究的一項統合分析中,共納入1,126名黃斑部病變患者、8,206名對照組,分析發現黃斑部病變者體內的維他命D值平均比沒有黃斑部病變者低15% (95%信賴區間[CI],-41%至11%),不過,這個差異未達顯著程度(P = .272)。
  
  另一篇分析中,體內的維他命D值居於最高的五分之一者,發生AMD的機率遠低於最少的五分之一者。相較於維他命D值最低者,維他命D值最高者發生AMD的機率減少83%(勝算比[OR]為0.83;95% CI, 0.71 - 0.97),後期AMD的機率降低47%(OR, 0.47;95% CI, 0.28 - 0.79)。
  
  此外,體內的維他命D值低於50 nmol/L的研究對象,發生後期AMD的風險是濃度較高者的2倍以上(OR, 2.18;95% CI, 1.34 - 3.56),不過,當考量所有AMD案例、不論病程階段時,這項關聯並不顯著(OR, 1.26;95% CI, 0.90 - 1.76)。
  
  雖然作者主張維他命D值低可能會造成AMD,但是維他命D缺乏可能無法完全解釋此情況之發生與惡化,另外,也還不清楚維他命D補充品是否可以預防發生AMD。
  
  他們也承認,目前沒有有效的理論可以完全解釋體內維他命D值和後期AMD的關聯,而較低的維他命D值也可能是因為黃斑部退化導致。
  
  作者們解釋,在這種情況下,原發性異常可能是因為AMD造成的視力偏低,其次是功能自主的相關損失、飲食攝取和日曬減少,最終引起維他命D缺乏。由單一篇縱向研究提出的這個假設儘管不是無效的,但是未獲以下事實支持,此處所用的大多數[ORs]值,都有校正身體質量指數和/或季節/陽光曝曬時間/休閒體育活動。
  
  資料來源:http://www.24drs.com/
  
  Native link:Low Vitamin D Levels Linked to Macular Degeneration Risk

Low Vitamin D Levels Linked to Macular Degeneration Risk

By Tara Haelle
Medscape Medical News

Adults with the lowest concentrations of circulating 25-hydroxyvitamin D (25OHD) had the highest risk for age-related macular degeneration (AMD), according to a new systematic review and meta-analysis published online April 2 in Maturitas.

"The findings of the present meta-analysis strengthen the idea that there might be a link between vitamin D deficiency and AMD, notably at the late stages of the disease (P=0.002)," write Cedric Annweiler, MD, PhD, from Angers University Hospital in France, and colleagues. "It may therefore be possible that correction of vitamin D deficiency could improve the prognosis of AMD."

The researchers used a Medline search through November 2015 to identify 11 studies that met their selection criteria, out of an initial 243 found. The criteria included observational or interventional studies and outcomes based on data about AMD diagnoses (in at least one eye) and circulating vitamin D concentration.

Among the studies, seven were cross-sectional, one was a case series, one was a case–control study, one was a retrospective longitudinal cohort study, and one was a discordant sibling cohort. They ranged in size from 65 to 17,045 participants; from 31 to 1440 participants had AMD. The researchers categorized AMD as whole, early, or late. All the studies had been published since 2007.

A meta-analysis of three studies, including 1126 participants with macular degeneration and 8206 without, found that those with macular degeneration had circulating vitamin D levels an average 15% (95% confidence interval [CI], ?41% to 11%) lower than those without macular degeneration, but the difference was not significant (P = .272).

In a second analysis, those in the highest quintile of circulating vitamin D levels had the lowest odds of AMD compared with those in the lowest quintile. Those with the highest vitamin D levels had 83% lower odds of AMD (odds ratio [OR], 0.83; 95% CI, 0.71 - 0.97) and 47% lower odds of late AMD (OR, 0.47; 95% CI, 0.28 - 0.79) compared with those with the lowest levels.

In addition, participants with less than 50 nmol/L circulating vitamin D had more than twice the odds of late AMD (OR, 2.18; 95% CI, 1.34 - 3.56) than those with higher concentrations. However, this association dropped out of significance when all AMD cases, regardless of stage, were considered (OR, 1.26; 95% CI, 0.90 - 1.76).

Although the authors argue for the possibility that low vitamin D levels may contribute to AMD, they state that vitamin D deficiency may not fully explain development and worsening of the condition. Further, it is unclear whether vitamin D supplementation would be protective against developing AMD.

They also acknowledge that no validated theory currently exists that can fully explain an association between circulating vitamin D levels and late-stage AMD, and that lower vitamin D levels may result from macular degeneration.

"In this scenario, the primary abnormality would be low vision due to AMD, followed by related loss of functional autonomy, reduction in dietary intakes and sunlight exposure, which can ultimately cause vitamin D deficiency," the authors explain. "This hypothesis, although not invalidated by the single longitudinal study reported here, was yet not supported by the fact that most [ORs] used here were adjusted for body mass index and/or for season/sunlight exposure time/recreational physical activity."

No external funding was used for the study. The authors have disclosed no relevant financial relationships.

Maturitas. Published online April 2, 2016.

    
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