Background: Well conducted meta-analyses (MAs) are considered to be one of the best sources of evidence. However, MAs with methodological flaws may introduce bias and mislead evidence users. The aim of this study is to investigate the characteristics and methodological quality of MAs on diabetes mellitus (DM) treatments.
Objectives: To assess the characteristics and methodological quality of MAs on DM treatments by conducting a cross-sectional study.
Methods: The Cochrane Database of Systematic Review and Database of Abstract of Reviews of Effects were searched for relevant MAs. We used the AMSTAR (A MeaSurement Tool to Assess systematic Reviews) tool to assess the methodological quality of the included MAs. Logistic regression analysis was used to identify association between characteristics of MA and AMSTAR results.
Results: A total of 215 MAs including 4364 primary studies and 13,402,401 participants were included. Over half of the MAs (66.1%) only included type-2 DM patients and 129 MAs (60.0%) were focused on pharmacological treatments; 90.7% of MAs performed a comprehensive literature search and 87.4% provided characteristics of included studies. The included MAs generally had a poor performance on the remaining AMSTAR items, especially in assessing publication bias (35.3%), providing lists of studies (20.9%) and declaring sources of support comprehensively (6.1%). Only 59.5% of MAs mentioned harms of interventions. MAs in which the corresponding author came from Asia performed less well in providing MA protocols than those from Europe.
Conclusions: Methodological quality of MA on DM treatments was unsatisfactory. There is considerable room for improvement, especially in assessment of publication bias, provision of lists of studies and declaring sources of support comprehensively. It is also recommended that MA authors also report harms of treatment.