Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada.
Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA.
Am J Clin Nutr. 2021 Jun 1;113(6):1578-1592. doi: 10.1093/ajcn/nqab002.
Dietary recommendations and policies should be guided by rigorous systematic reviews. Reviews that are of poor methodological quality may be ineffective or misleading. Most of the evidence in nutrition comes from nonrandomized studies of nutritional exposures (usually referred to as nutritional epidemiology studies), but to date methodological evaluations of the quality of systematic reviews of such studies have been sparse and inconsistent.
We aimed to investigate the quality of recently published systematic reviews and meta-analyses of nutritional epidemiology studies and to propose guidance addressing major limitations.
We searched MEDLINE (January 2018-August 2019), EMBASE (January 2018-August 2019), and the Cochrane Database of Systematic Reviews (January 2018-February 2019) for systematic reviews of nutritional epidemiology studies. We included a random sample of 150 reviews.
Most reviews were published by authors from Asia (n = 49; 32.7%) or Europe (n = 43; 28.7%) and investigated foods or beverages (n = 60; 40.0%) and cancer morbidity and mortality (n = 54; 36%). Reviews often had important limitations: less than one-quarter (n = 30; 20.0%) reported preregistration of a protocol and almost one-third (n = 42; 28.0%) did not report a replicable search strategy. Suboptimal practices and errors in the synthesis of results were common: one-quarter of meta-analyses (n = 30; 26.1%) selected the meta-analytic model based on statistical indicators of heterogeneity and almost half of meta-analyses (n = 50; 43.5%) did not consider dose-response associations even when it was appropriate to do so. Only 16 (10.7%) reviews used an established system to evaluate the certainty of evidence.
Systematic reviews of nutritional epidemiology studies often have serious limitations. Authors can improve future reviews by involving statisticians, methodologists, and researchers with substantive knowledge in the specific area of nutrition being studied and using a rigorous and transparent system to evaluate the certainty of evidence.
饮食建议和政策应遵循严格的系统评价。方法学质量差的评价可能无效或具有误导性。营养方面的大多数证据来自营养暴露的非随机研究（通常称为营养流行病学研究），但迄今为止，对这些研究系统评价质量的方法学评估还很少且不一致。
我们旨在调查最近发表的营养流行病学研究系统评价和荟萃分析的质量，并提出解决主要局限性的指导意见。
我们在 MEDLINE（2018 年 1 月至 2019 年 8 月）、EMBASE（2018 年 1 月至 2019 年 8 月）和 Cochrane 系统评价数据库（2018 年 1 月至 2019 年 2 月）中搜索营养流行病学研究的系统评价。我们纳入了 150 篇随机选择的综述。
大多数综述的作者来自亚洲（n=49；32.7%）或欧洲（n=43；28.7%），研究的是食物或饮料（n=60；40.0%）和癌症发病率和死亡率（n=54；36.0%）。综述通常存在重要的局限性：不到四分之一（n=30；20.0%）报告了方案的预先注册，近三分之一（n=42；28.0%）没有报告可重复的搜索策略。结果综合中的不当做法和错误很常见：四分之一的荟萃分析（n=30；26.1%）根据异质性的统计指标选择荟萃分析模型，几乎一半的荟萃分析（n=50；43.5%）即使在适当的情况下也没有考虑剂量-反应关系。只有 16 篇（10.7%）综述使用了既定的系统来评估证据的确定性。
营养流行病学研究的系统评价通常存在严重的局限性。作者可以通过让统计学家、方法学家和在研究特定营养领域具有实质性知识的研究人员参与，并使用严格透明的系统来评估证据的确定性，从而改进未来的综述。
