OBJECTIVES: To compare the prevalence of periodontal disease between two randomly selected population-based studies (the Oral Infections and Vascular Disease Epidemiology Study (INVEST) and the Study of Health in Pomerania (SHIP)) and address relevant methodological issues.
METHODS: Comparison was restricted to 55- to 81-year olds. Attachment loss (AL), probing depth (PD) and tooth count were assessed in INVEST (full-mouth, six sites) and SHIP (half-mouth, four sites). Subjects were classified according to the CDC/AAP case definition. Recording protocols were standardized. Mixed linear or logistic models were used to compare INVEST with SHIP.
RESULTS: Mean half-mouth AL was lower in INVEST versus SHIP (INVEST: 2.9 mm versus SHIP: 4.0 mm, p < 0.05). Findings were similar across multiple periodontal disease definitions. After equalization of recording protocols and adjustment for periodontal risk factors, mean AL and PD were 1.2 and 0.3 mm lower in INVEST versus SHIP (p < 0.001). The odds for severe periodontitis (CDC/AAP) was 0.2-fold in INVEST versus SHIP (p < 0.001). Confounding effects of age, gender, race/ethnicity, education and use of interdental care devices were highest as indicated by change-in-estimate for study.
CONCLUSION: Implementation of the proposed method for comparison of epidemiological studies revealed that periodontitis was less prevalent in INVEST compared with SHIP, even after extensive risk-factor adjustment.