Evaluation of Morphology and Biochemical Parameters of Young Adults Using Heated Tobacco Products in Poland: A Case-Control Study

<b>Background/Objectives:</b> Little is currently known of the impact of heated tobacco on health. The aim of this study is to evaluate the impact of heated tobacco use on selected health assessment parameters among people aged 18-30 to determine the effect on health status. <b>Methods:</b> A case-control study was conducted from April 2022 to February 2025. A total of 195 young, healthy adult residents of Lodz, Poland, took part. The participants were divided into three groups: IQOS (I-Quit-Ordinary-Smoking) smokers who had never smoked or who had quit smoking six months previously (<i>n</i> = 65); daily smokers who had smoked at least five cigarettes per day for at least one year and had not used any other smoking substitutes for at least one year (<i>n</i> = 65); and people who have never smoked or used tobacco products (<i>n</i> = 65). Blood samples from 37 IQOS users (57%), 28 traditional cigarette smokers (43%), and 45 non-smokers (69%) were submitted for laboratory analysis. The tested parameters were determined in the diagnostic laboratory of the Bonifratów Hospital in Lodz. <b>Results:</b> No significant differences (<i>p</i> > 0.05) were found between the groups with regard to blood count (white blood cell count (WBC), red blood cell count (RBC), lymphocytes, monocyte number (MONO), hemoglobin concentration (HGB)), biochemical biomarkers (C-reactive protein (CRP), fibrinogen, apolipoprotein A1 (apo A1), apolipoprotein B (apo B), glucose), or lipid profile (total cholesterol, triglycerides (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL)). The cigarette smokers demonstrated significantly higher uric acid levels compared to the IQOS users and non-smokers: 5.22 vs. 4.77 vs. 4.40 mg/dL (<i>p</i> < 0.01). The IQOS users demonstrated significantly higher platelet count levels compared to cigarette smokers and non-smokers: 290.27 vs. 267.14 vs. 256.33 × 10³/ μL (<i>p</i> < 0.05). Among the IQOS users (<i>n</i> = 37), the level of glucose (ρ = -0.47; <i>p</i> = 0.01), WBC (ρ = -0.36; <i>p</i> = 0.03), lymphocytes (ρ = -0.38; <i>p</i> = 0.02), and uric acid (ρ = -0.34; <i>p</i> = 0.04) was negatively correlated with the daily number of heated tobacco sticks. The HDL level was positively correlated (ρ = 0.39; <i>p</i> = 0.02) with the daily number of heated tobacco sticks. <b>Conclusions:</b> Further cohort studies assessing the health status of young users of heated nicotine products and prospective analyses are necessary.