Hematological Parameters in Young Users of Heated Tobacco Products in Poland-A Case-Control Study.

Background/Objectives: Young people are very susceptible to the marketing of technological devices and more frequently reach for heated tobacco products. There has been little research on how these products affect human health. The aim of the study was to assess the impact of heated tobacco use on hematological and biochemical parameters in young people. Methods: A case-control study was conducted in the years 2022-2025 among 200 healthy young individuals aged 18-30. The participants were divided into three groups, i.e., traditional cigarette smokers (DS), IQOS users (IQOS), and non-smokers (NS). Blood samples were collected from 111 subjects (38 IQOS, 28 DS and 45 NS), and morphological parameters were determined in the diagnostic laboratory at the Hospital of Brothers Hospitallers of St. John of God in Lodz. Results: Among the blood parameters analyzed, which did not follow a normal distribution, statistically significant differences in median values were identified between the NS, IQOS, and DS groups for uric acid (p < 0.01), hemoglobin (p < 0.05), mean corpuscular hemoglobin concentration (MCHC) (p < 0.05), and plateletcrit (PCT) (p < 0.01). Post hoc analysis revealed significant differences in uric acid levels between the NS and DS groups (4.3 vs. 5.2). For hemoglobin, statistically significant differences (p < 0.05) were found between the NS and IQOS groups (13.7 vs. 14.4). For MCHC, significant differences were also observed between the NS and IQOS groups (32.9 vs. 33.7). Among the multiple linear regression models, developed for variables with a normal distribution, only two models achieved an adjusted R2 above 0.4. In the model predicting red blood cells (RBC) levels, the adjusted R2 was 0.459. Two independent variables were significant, i.e., male sex (Beta = 0.703; p < 0.001) and DS compared to IQOS (Beta = -0.242; p < 0.01). The second model, predicting hematocrit levels, achieved an adjusted R2 of 0.458. Significant effects were noted for male sex (Beta = 0.700; p < 0.001) and DS versus IQOS (Beta = -0.235; p < 0.01). Conclusions: Monitoring hematological parameters can be used as an early predictor of morbidity in IQOS users. Therefore, there is a need for long-term studies that follow users over an extended period.