Respiratory Function, Physical Capacity, and Metabolic Syndrome Components in Combustible Cigarettes and Heated Tobacco Products Users: A Four-Year Follow-Up Cohort Study

Purpose: Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide and is the fourth leading cause of death in Kazakhstan. Cigarette smoking is a prevalent risk factor for COPD. While quitting smoking is the preferred way to reduce COPD risk, literature suggests that heated tobacco products (HTP) might be a better option for people who cannot quit smoking. The aim of this paper was to analyze the long-term effects of shifting to HTP use in long-term smokers compared to continued combustible cigarettes (CC) use. Patients and methods: A cohort of 1200 participants (400 HTP and 800 CC) aged 40-59 years with a minimum of 10 pack-year smoking history were recruited and followed for four years. The functional outcomes compared between HTP and CC users included: (1) COPD Assessment Test (CAT); (2) post-bronchodilator lung function; (3) 6-minute walking distance (6MWD) test; and (4) metabolic syndrome components. One way ANOVA was used to compare functional outcomes between visits, while multivariable linear mixed models were used to test associations between health outcomes and smoking type (HTP vs. CC) over time. Results: Out of 1200 participants 893 (609 CC users and 284 HTP users) remained in the study by the fourth year of follow up. Comparison between functional outcomes showed that most of them have improved between visits, while lung function and fasting blood glucose levels got worse. Linear mixed models showed HTP use was associated with better functional outcomes over time compared to CC users. Lung function decrease was significantly less in HTP users, while improvements in CAT scores, waist circumference, and systolic blood pressure were significantly better compared to CC users. Conclusion: This study demonstrated that HTP users experienced it to a significantly lesser decrease in lung function compared to CC users, while demonstrating better improvements in other functional outcomes. The results of this study suggest that HTP might be a less deleterious alternative compared to CC in people with long history of CC use and who cannot quit smoking.