Switching from cigarette use to dual use with heated tobacco products and severe periodontitis risk

Introduction: Severe periodontitis is a major global health concern, yet the impact of switching from combustible cigarettes to dual use of combustible cigarettes and heated tobacco products on periodontal status remains unclear. This study aimed to examine whether changes in smoking status influence the risk of severe periodontitis among Japanese adults. Methods: We conducted a longitudinal analysis using panel data from the Japan COVID-19 and Society Internet Survey. Participants were daily combustible cigarette smokers with periodontitis in 2021 and were followed through 2023. Smoking trajectories between 2021 and 2022 were categorized as: (1) continuous combustible cigarette smokers, (2) dual users (heated tobacco product-dominant), (3) dual users (combustible cigarette-dominant), and (4) quitters/reduced smokers. Severe periodontitis in 2023 was defined using validated self-reported criteria. Modified Poisson regression with robust variance was applied to estimate risk ratios and 95% confidence intervals (95% CIs), adjusting for potential confounders (age, sex, educational attainment, occupational status, marital status, equivalent income, alcohol consumption, diabetes mellitus status, periodontal pain, and smoking frequency). Results: A total of 193 participants (mean age 57.6 years; men 67.9%) were analyzed. Over 2 years, 61.1% developed severe periodontitis. Compared to continuous combustible cigarette smokers, the adjusted risk of severe periodontitis was 1.19 times (95% CI: 0.67-2.11), 1.41 times (95% CI: 1.04-1.91), and 0.99 times (95% CI: 0.76-1.28) higher for dual users (heated tobacco product-dominant), dual users (combustible cigarette-dominant), and quitters/reduced smokers, respectively. Sensitivity analyses using inverse probability weighting yielded consistent findings. Conclusion: Switching from daily combustible cigarette smoking to dual use with heated tobacco products may increase the risk of severe periodontitis. Combining combustible cigarettes with heated tobacco products, regardless of the frequency of combustible cigarette smoke, should not be considered a harm-reduction strategy in dental and public health practice.