Associations of Conventional Cigarette Smoking Intensity and Subjective Sleep Quality with Periodontal Status and Oral Health-Related Quality of Life: A Cross-Sectional Clinic-Based Study

Background and objectives: Smoking is an established risk factor for periodontitis, whereas periodontitis and poor sleep may adversely affect oral health-related quality of life (OHRQoL). This study examined whether conventional cigarette smoking intensity shows differential associations with periodontal status and OHRQoL while accounting for subjective sleep quality and sociodemographic characteristics. Materials and Methods: This cross-sectional study included 504 consecutive adult patients attending a university dental clinic in Bulgaria. Periodontal status was determined according to the 2017 World Workshop classification. Sleep quality and OHRQoL were assessed using the Pittsburgh Sleep Quality Index (PSQI) and Oral Health Impact Profile-14 (OHIP-14). Multivariable binary logistic regression evaluated the association between smoking intensity and periodontitis, and hierarchical multiple linear regression with bias-corrected and accelerated bootstrap confidence intervals evaluated associations with OHIP-14. Analyses of conventional cigarette smoking included 477 participants. Results: Compared with no current smoking, smoking 10–20 cigarettes/day was associated with 5.7-fold higher adjusted odds of periodontitis (OR = 5.726; 95% CI: 1.934–16.956), whereas >20 cigarettes/day was associated with 16.1-fold higher odds (OR = 16.148; 95% CI: 2.127–122.582). Smoking intensity was not associated with PSQI scores. In the OHIP-14 model, smoking intensity increased the explained variance by 4.0% beyond sociodemographic characteristics (p < 0.001), followed by a further 6.4% increase after the addition of periodontal status and PSQI (p < 0.001). Periodontitis (B = 3.986; BCa 95% CI: 1.510–6.473) and higher PSQI scores (B = 0.741; BCa 95% CI: 0.452–1.031) were associated with higher OHIP-14 summary scores in the fully adjusted model. Category-specific adjusted smoking associations with OHIP-14 were heterogeneous and did not increase monotonically with smoking intensity. Conclusions: Higher-intensity conventional cigarette smoking was strongly associated with periodontitis, whereas its adjusted association with OHRQoL was smaller and heterogeneous across smoking-intensity categories. Periodontal status and higher PSQI scores were associated with greater patient-perceived oral health burden after multivariable adjustment. Smoking-related estimates should be interpreted with consideration that the “no current smoking” reference category may have included former smokers because previous smoking history was unavailable.