Differences in the reporting of conflicts of interest and sponsorships in systematic reviews with meta-analyses in dentistry: an examination of factors associated with their reporting.

Background: Reporting conflicts of interest (COI) and sources of sponsorship are of paramount importance in adequately interpreting the results of systematic reviews. Some evidence suggests that there is an influence of COI and sponsorship on the study results. The objectives of this meta-research study were twofold: (a) to assess the reporting of COI and sponsorship statements in systematic reviews published in dentistry in three sources (abstract, journal's website and article's full text) and (b) to assess the associations between the characteristics of the systematic reviews and reporting of COI.

Methods: We searched the PubMed database for dental systematic reviews published from database inception to June 2023. We assessed how COI and sponsorship statements were reported in the three sources. We performed a logistic regression analysis to assess the associations between the characteristics of the systematic reviews and the reporting of COI.

Results: We assessed 924 abstracts published in PubMed and on the corresponding journals´ websites. Similarly, full texts associated with the 924 abstracts were also assessed. A total of 639 (69%) and 795 (88%) studies had no statement of COI in the abstracts on PubMed and the journal's website, respectively. In contrast, a COI statement was reported in 801 (87%) full texts. Sponsorship statements were not reported in 911 (99%) and 847 (93%) abstracts published in PubMed and a journal´s website, respectively. Nearly two-thirds of the full-text articles (N = 607) included sponsorship statements. Journal access was significantly associated with COI statement reporting in all three sources. Open-access journals have significantly higher odds to report COI in PubMed and full-texts, while have significantly lower odds to report COI in the websites, compared with subscription or hybrid journals. Abstract type was significantly associated with COI statement reporting on the journal's website and in the full text. Review registration based on the full text and the number of authors were significantly associated with COI statement reporting in PubMed and in the full texts. Several other variables were found to be significantly associated with COI statement reporting in one of the three sources.

Conclusions: COI and sponsorship statements seem to be underreported in the abstracts and homepage of the journals, compared to the full-texts. These results were particularly more pronounced in abstracts published in both the PubMed database and the journals' websites. Several characteristics of systematic reviews were associated with COI statement reporting.