Background:
Tobacco companies are investing massive amounts of money to support research on heated tobacco products (HTP) and tobacco harm reduction (THR).

Objective:
To quantify the proportion of research on HTP funded by the tobacco industry and to assess any association between the funding by the tobacco industry -and the corresponding presence of conflicts of interest (COI)- and how the authors interpreted findings of their studies.

Methods:
We conducted a systematic review of the literature through 23rd February 2022 in Pubmed/Medline, Embase and the Cochrane Library to identify all publications focusing on HTPs (PROSPERO 2020: CRD42020137394). For each study, reported tobacco industry related COI was identified based on authors’ affiliations, acknowledgements, funding, and COI disclosure. Two trained reviewers, blinded to information on authors, independently evaluated the conclusions of the abstracts to categorize them as anti-HTPs/THR (providing conclusions against or strongly against HTPs or THR); neutral; or pro-HTPs/THR (providing conclusions in favour or strongly in favour to HTPs or THR).

Results:
Out of 498 included eligible studies, 192 (38.6%) had tobacco-related COIs. Five studies with a declared COI were among the 194 studies assessed as anti-HTPs/THR (2.6%), 20 studies with COI were among 94 neutral studies (21.3%), and 167 were among the 210 studies evaluated as pro-HTPs/THR (79.5%). The adjusted odds ratio of being pro-HTPs/THR was 23.3 (95% confidence interval: 11.6 to 46.7) for studies with a COI.

Conclusions:
The existing body of published research on HTPs is dominated by studies conducted or supported by the tobacco industry, with evidence of bias in their conclusions. The large majority of COI-free studies oppose HTPs. There is an urgent need to fund and sustain independent research on novel tobacco products.