Studies with statistically significant effect estimates are more frequently published compared to non-significant estimates in oral health journals

BACKGROUND: Studies reporting statistically significant effect estimates tend to be more frequently published compared to studies reporting non-significant or equivalent estimates. Consequently, this may lead to distortion of the literature. The aim of this study is to assess the prevalence of reporting statistically significant effect estimates in leading oral health journals and to explore associations between the effect estimates and record characteristics. METHODS: An electronic database search was undertaken of a selection of leading oral health journals including general oral health journals to identify primary oral health records published in 2019. Descriptive statistics and population average GEE logistic regression model was used to assess associations between articles reporting a statistically significant effect estimate and the record characteristics. RESULTS: In 1335 records, 82.4% records reported a statistically significant effect estimate. All speciality journals compared to general oral health journals were less likely to publish a record with significant effect estimates. Authors based in Asia or other (OR 1.49; 95% CI :1.02,2.19; p = 0.037) were more likely to report significant effect estimates compared to those based in Europe. Interventional (OR 0.35; 0.22,0.58; p < 0.001) and observational (OR 0.56; 0.36, 0.89; p = 0.013) records were less likely to report significant effect estimates compared to in-vitro studies. Registered records were less likely to report significant effect estimates when compared to non-registered studies (OR 0.22; 95% CI :0.14,0.32; p < 0.001). CONCLUSION: The publishing of records with significant effect estimates is prevalent within the oral health literature. To reduce dissemination bias and overestimation of effect sizes in systematic reviews, the publishing of studies with non-significant or equivalent effect estimates should be encouraged.