This thesis investigates the genetic characteristics and determinants linked to smoking behaviours and explores the influence of smoking on gene expression in CAD patients. Studying these health-related behaviours can improve the well-being of the Roma minority population. Additionally, the impact of smoking on the blood transcriptome in Hungarian CAD patients remains understudied. These findings would be valuable in strengthening existing epidemiological evidence, identifying relevant determinants, and informing targeted interventions. This thesis was based on two observational studies. The first was a comprehensive health survey with 814 participants comprising 412 HG and 402 HR. The study compared risk allele frequencies using GRS and wGRS based on data of ten SNPs. HR individuals exhibited significantly higher smoking frequency (33% higher) and tended to start smoking at a younger age (standardized β = -0.23, p <0.001). However, despite the high prevalence of smoking behaviours and nicotine dependence among HR individuals, the study found no significant genetic influence, as median GRS values did not differ significantly, although wGRS was slightly higher among Roma individuals (5.2 vs 4.9; p = 0.02). Additionally, an inverse relationship between SES and smoking behaviours was observed, with smokers showing lower SES (βHR = -0.039, p = 0.023; βHG = -0.010, p = 0.049). The second analysis was based on 61 CAD patients with a median age of 67 years, and only 44 subjects were included for further analyses. Between SM and NSM, 120 DEGs (15 upregulated and 105 downregulated) were identified with a fold change (FC) ≥1.5 and a p-value <0.05. GO analyses revealed that the upregulated genes were related to immune response pathways (FDR≤0.03). In contrast, downregulated genes exhibited significant annotations with pathways involving oxygen and haem binding or activity (FDR≤0.03).
Our first analysis provides evidence of higher smoking frequency and early initiation among HR individuals, but these behaviours are not genetically influenced. The inverse relationship between SES and smoking behaviours highlights the importance of considering socioeconomic factors when studying and addressing smoking habits. On the other hand, the second study offers valuable insights into the potential effects of smoking on gene expression in whole blood and their connection to smoking-related CAD. The previously unexplored overexpression of RCAN3, TRAV4, and JCHAIN genes indicates a possible involvement in CAD among individuals who smoke.