Smoking and central obesity have both been linked to periodontitis, but their combined relationship with periodontal disease may be influenced by demographic and behavioral factors. This cross-sectional study analyzed records of 420 adult dental patients attending the College of Dentistry at the University of Baghdad. Data included demographic characteristics, smoking status, periodontal clinical findings, body mass index (BMI), and waist-to-height ratio (WHtR). Periodontitis was defined according to the 2018 classification framework, and logistic regression models were used to examine the associations of smoking and obesity-related indicators with periodontitis. The overall prevalence of periodontitis was 36.4%. Participants with periodontitis were significantly older than those without periodontitis (46.0 vs. 28.9 years; p < 0.0001). In the fully adjusted model, age remained the strongest factor associated with periodontitis (OR = 1.15 per year; 95% CI: 1.11–1.18; p < 0.001). The apparent association between smoking and periodontitis was substantially influenced by age, as current smoking was more common among younger participants in this sample. The association between smoking status and periodontitis appeared to differ according to WHtR category (interaction term p = 0.016); however, this finding should be interpreted cautiously because of the cross-sectional design and age imbalance across exposure groups. Overall, the findings suggest that age was the dominant factor associated with periodontitis in this dental patient sample, while the relationship between smoking, central obesity, and periodontitis requires further investigation in longitudinal studies with detailed smoking and metabolic data.