Joint trajectories of periodontal disease and type 2 diabetes burden across 204 countries.

OBJECTIVE: To test whether countries exhibit reproducible joint longitudinal patterns of periodontal disease and type 2 diabetes burden rather than a homogeneous global trajectory. METHODS: This ecological study analysed age-standardised incidence, prevalence and disability-adjusted life-year rates for both conditions in 204 countries. Six annual trajectories were log-transformed, standardised and clustered using multivariate dynamic time warping with partitioning around medoids. Stability was assessed by 200 country-bootstrap replicates, an earlier observation window and principal-component k-means clustering. RESULTS: Three ecological trajectory phenotypes were identified, comprising 19, 89 and 96 countries. They represented diabetes-dominant with periodontal decline, lower diabetes with intermediate periodontal burden, and high joint burden. The median bootstrap adjusted Rand index was 0.866; earlier-window and alternative-algorithm indices were 0.911 and 0.900, respectively. Shape-only clustering showed minimal agreement (0.010), indicating that burden magnitude materially defined the groups. CONCLUSIONS: National periodontal and type 2 diabetes burdens do not follow a single shared pattern. Reproducible ecological groupings may support integrated oral and metabolic health planning, but they neither demonstrate individual comorbidity nor establish a causal relationship.