Interplay between vitamin D receptor FokI polymorphism and smoking influences Porphyromonas gingivalis proportions in subgingival plaque

Aim This cross-sectional study investigated the effect of the vitamin D receptor (VDR) FokI polymorphism and its interactions with smoking/drinking on the proportions of periodontal pathogens and periodontitis severity. Materials and Methods FokI genotyping and bacterial quantification were performed using real-time polymerase chain reaction. Periodontitis severity was determined using mean clinical attachment level (CAL). Regression analyses examined the associations between the FokI polymorphism (rs2228570) and bacterial proportions or periodontitis severity. Effect modification by smoking or drinking was assessed. Results The study population comprised 1,460 individuals, aged 39-66 years. After multivariable adjustment, the FokI risk genotypes (CC + CT) were associated with elevated Porphyromonas gingivalis proportions (regression coefficient (beta) =0.294 +/- 0.139; p = .034) and increased mean CAL (beta = 0.130 +/- 0.048; p = .007). The effect of the FokI polymorphism on P. gingivalis proportions was greater in smokers (beta = 0.897 +/- 0.328; p = .006) compared to non-smokers (beta = 0.164 +/- 0.153; p = .282) and in drinkers (beta = 0.668 +/- 0.242; p = .006) compared to non-drinkers (beta = 0.114 +/- 0.169; p = .500). The genotype*smoking interaction for P. gingivalis proportions was significant (p = .043), whereas the genotype*drinking interaction was not (p = .061). Similar results were found for the effect of the genotype*smoking/drinking interaction on mean CAL. Conclusions These findings suggest that the interplay between the host genotype and smoking is important in determining the subgingival microbial composition and periodontitis severity.