Western Australian Centre for Health and Ageing, Medical School (M577), University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia.
Drugs Aging. 2019 May;36(5):419-434. doi: 10.1007/s40266-019-00649-w.
Vitamin B deficiency and elevated total plasma homocysteine have been associated with cognitive impairment and dementia in later life, although it is unknown if treatment with these vitamins improves cognitive outcomes.
The objectives of this study were to examine the efficacy of treatment with vitamin B, vitamin B, or folic acid in slowing cognitive decline amongst older adults with and without cognitive impairment.
We summarized findings from previous systematic reviews of clinical trials and performed a new systematic review and meta-analysis of 31 English-language, randomized placebo-controlled trials of B-vitamin supplementation of individuals with and without existing cognitive impairment.
Previous reviews have generally reported no effect of B vitamins on cognitive function in older adults with or without cognitive impairment at study entry, although these vitamins effectively lowered total plasma homocysteine levels in participants. Ten randomized placebo-controlled trials of 1925 participants with pre-existing cognitive impairment and 21 trials of 15,104 participants without cognitive impairment have been completed to date but these generally confirmed findings from previous reviews with the exception of two trials that showed a modest but clinically uncertain benefit for vitamins in people with elevated plasma homocysteine. B-vitamin supplementation did not show an improvement in Mini-Mental State Examination scores for individuals with (mean difference 0.16, 95% confidence interval - 0.18 to 0.51) and without (mean difference 0.04, 95% confidence interval - 0.10 to 0.18) cognitive impairment compared to placebo.
Raised total plasma homocysteine is associated with an increased risk of cognitive impairment and dementia, although available evidence from randomized controlled trials shows no obvious cognitive benefit of lowering homocysteine using B vitamins. Existing trials vary greatly in the type of supplementation, population sampled, study quality, and duration of treatment, thereby making it difficult to draw firm conclusions from existing data. Findings should therefore be viewed in the context of the limitations of the available data and the lack of evidence of effect should not necessarily be interpreted as evidence of no effect.
维生素 B 缺乏和血浆同型半胱氨酸水平升高与晚年认知障碍和痴呆有关，尽管尚不清楚这些维生素的治疗是否能改善认知结果。
本研究旨在观察维生素 B 联合治疗、维生素 B 单一治疗或叶酸治疗是否能减缓认知障碍老年人和认知正常老年人的认知能力下降。
我们总结了之前对临床试验进行的系统评价的结果，并对 31 项英语随机安慰剂对照试验进行了新的系统评价和荟萃分析，这些试验评估了维生素 B 补充剂对有和无认知障碍的个体的疗效。
以前的综述通常报告称，在认知障碍和无认知障碍的老年人中，B 族维生素对认知功能没有影响，尽管这些维生素能有效降低参与者的血浆总同型半胱氨酸水平。目前已经完成了针对有认知障碍的 1925 名参与者的 10 项随机安慰剂对照试验和针对无认知障碍的 15104 名参与者的 21 项试验，但这些试验结果与以前的综述基本一致，只有两项试验显示补充维生素 B 对血浆同型半胱氨酸升高的人有适度但不确定的益处。B 族维生素补充剂对有认知障碍的人（平均差异 0.16，95%置信区间 -0.18 至 0.51）和无认知障碍的人（平均差异 0.04，95%置信区间 -0.10 至 0.18）的简易精神状态检查评分没有改善。
血浆总同型半胱氨酸升高与认知障碍和痴呆的风险增加有关，尽管随机对照试验的现有证据表明，使用 B 族维生素降低同型半胱氨酸并没有明显的认知益处。现有的试验在补充类型、抽样人群、研究质量和治疗持续时间等方面差异很大，因此很难从现有数据中得出明确的结论。因此，应根据现有数据的局限性来看待这些结果，缺乏效果的证据不应被解读为没有效果的证据。
