Conclusiveness of the Cochrane Reviews in Nutrition: a systematic analysis

BACKGROUND/OBJECTIVE: To assess the conclusiveness of the Cochrane Reviews (CRs) in the field of Nutrition, we tested the hypotheses that: (1) the majority of CRs is inconclusive; (2) the majority of CRs recognizes the need for further and better studies and (3) the ability to reach a conclusion is dependent on the number of studies performed and number of patients enrolled. SUBJECTS/METHODS: We selected all 87 CRs in the field of Nutrition available in Cochrane library. Each CR was analyzed for the number of randomized clinical trials (RCTs) found, number of RCTs included for analysis, number of patients enrolled, the stated need for further studies and the reason(s) for it and the conclusiveness of the CR. RESULTS: Fifty-six out of eighty-seven CRs (64.4%) were conclusive. The average number of available articles, the percentage of articles included, the average number of RCT's retained in the analyses and the total cumulative number of patients enrolled in the studies retained for analysis were significantly higher in conclusive CRs than in non-conclusive ones. The majority of inconclusive CRs (70.9%) recognized the need for further studies, a percentage not significantly different from that found in conclusive ones (58.9%, P = 0.26). The percentage of conclusive CRs was not affected by year of publication. CONCLUSIONS: The majority of CRs in Nutrition is conclusive, but most of them emphasize the need for further studies. The ability for a CR to reach a conclusion is affected by the cumulative patient sample size and number of RCT's included in the analysis.