A 3-year longitudinal study of the distribution of periodontitis severity and association between disease progression and risk factors: Nagasaki Islands Study

Quantifying periodontitis in a meaningful and reproducible manner has been an ongoing challenge for oral epidemiologists and clinicians. Heterogeneity of case definitions affects comparison of the results and leads to either overestimation or underestimation of periodontitis prevalence. However, few epidemiological studies have analysed data according to the latest 2018 classification. In this study, we aimed to determine the prevalence of periodontitis severity and its progression according to the 2018 classification and to examine the associations between its progression and risk factors in the Nagasaki Islands Study. We recruited 1,358 participants who attended an oral examination at the baseline survey in a population-based prospective open-cohort study, followed up 533 participants at the second survey 3 years later, and analysed 496 (mean age, 66 (standard deviation, 10) years; 283 women (57%)). The prevalence of periodontitis severity and its progression using the 2018 classification were quantified. Logistic regression analysis was applied to analyse the association between disease progression and risk factors. Moreover, subgroup analyses were performed based on changes in periodontitis stage from baseline to the second survey. Overall, 3.2%, 55%, and 42% of participants had Stage I, II, and III/IV periodontitis, respectively; 70% of the participants retained the same stage as periodontitis severity between the baseline and second survey. Meanwhile, 15% shifted to a higher stage, and 15% shifted to a lower stage. During the 3-year period, 58% of participants exhibited disease progression. Multivariable logistic regression analysis revealed that older age (65–74 years old: odds ratio (OR) = 1.65, 95% confidence interval (CI) = 1.05 to 2.58; ≥ 75 years old: OR = 1.87: 95% CI = 1.05 to 3.33), being men (OR = 1.69, 95% CI = 1.12 to 2.55), and number of teeth present (1–9: OR = 0.24, 95% CI = 0.11 to 0.53; 20–23: OR = 1.81, 95% CI = 1.06 to 3.10) were associated with disease progression. Association between current smoking or diabetes medication use and its progression was not observed. Prevalence of Stage II and more periodontitis was 97% and 70% participants retained the same stage for 3 years. In addition, age, sex, and teeth present were associated with disease progression.