Abstract

To date, complete smoking cessation remaints the best method for protecting the health of both smokers and community. However, total cessation is a major challenging and many findings indicate a high risk of failure. In such cases, non-combustible tobacco products may serve as a measure for those who continue to smoke. This research investigates differences in respiratory finction and chronic lung disease status among adult former smokers between groups: (1) continued combustible cigarette smoking, (2) complete switching to non-combustible nicotine products, and (3) complete smoking cessation. A systematic search was conducted on Pubmed, Cochrane and Google Scholar for studies reporting FEV1, FVC, FEV1/FVC ratio, COPD exacerbations, respiratory symptoms, or lung cancer. Two independent reviewers performed screening, data extraction, quality assessment (STROBE), risk of bias evaluation (RoB2.0/ROBINS-I), and reliability of evidence. The stydy protocol was registered on PROSPERO (ID: CRD420251232685). Ten articles (6 RCT, 3 cohort studies, and 1 cross-sectional study) involing over 119,000 participants, with follow-up periods from 5 days to 20 years, were included in the analysis. According to the GRADE guidelines, the evidence is considered to have a moderate to low level of relibility. Therefore, complete cessation provides the greatest benefit for respitory function and reducing the risk of chronic lung disease. There is no certainty that non-combustible products may offer some benefits compared to continued smoking, there is currently no robus evidence regarding long-term improvement in respitory function or reduction in the risk of COPD and lung cancer. Futher research is required to strengthen the evidence base.