This study used the inverse variance heterogeneity (IVhet) model to conduct a reanalysis of a recent meta-analysis that reported a positive association, based on the random-effects (RE) model, between obesity and the incidence of type 2 diabetes and coronary heart disease, but not all-cause stroke, in adults. Data emanated from a recent meta-analysis of five Mendelian randomization studies representing 881,692 adults. Results were pooled using the IVhet model and reported as OR’s and 95% CI. Small-study effects were examined using the Doi plot and Luis Furuya-Kanamori (LFK) index. Influence analysis was also conducted. The association between obesity and type 2 diabetes, coronary heart disease, and all-cause stroke was, respectively, 1.38 (95% CI 1.00 to 1.90, p=0.05, I2 =93%), 1.10 (95% CI 0.90 to 1.35, p=0.35, I2 =87%), and 1.02 (95% CI 0.95 to 1.09, p=0.64, I2 =0%). Compared with the original RE model, results were similar for all-cause stroke, but point estimates for type 2 diabetes and coronary heart disease were smaller (29.3% and 9.8%) with wider (7.0% and 14.7%), overlapping CI. Major asymmetry suggestive of small-study effects was observed (LFK=3.59). With the exception of one study for type 2 diabetes, results remained uncertain (overlapping 95% CI) when each study was deleted from the model once. A lack of certainty exists regarding the association between obesity and the incidence of type 2 diabetes, coronary heart disease, and all-cause stroke in adults.
- type 2 diabetes
- coronary heart disease
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Contributors GAK was responsible for the conception and design, acquisition of data, analysis and interpretation of data, drafting the initial manuscript and revising it critically for important intellectual content. KSK was responsible for the conception and design, acquisition of data, drafting the initial manuscript and revising all drafts critically for important intellectual content. BLS was responsible for the conception and design, drafting the initial manuscript and revising all drafts critically for important intellectual content. All authors read and approved the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Ethics approval Given that this study was based on a meta-analysis of existing, publicly available aggregate data, this study was exempt from institutional review board approval.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data are available upon reasonable request.
Patient consent for publication Not required.