Age of type 2 diabetes onset as a risk factor for dementia: A 13-year retrospective cohort study

Aims: To examine whether age at type 2 diabetes onset is an independent predictor of dementia risk. Methods: Retrospective cohort drawn from healthcare administrative records of all inhabitants within Romagna's catchment area, Italy, with an estimated onset of type 2 diabetes in 2008–2017 and aged ≥ 55, with follow-up until 2020. Time to dementia or censoring was estimated with the Kaplan–Meier method, using diabetes onset as the time origin. Age groups were compared with the log-rank test. Multivariable competing-risks analysis was used to assess predictors of dementia. Results: In patients aged ≥ 75 years, dementia-free survival (DFS) declined to below 90 % within five years and linearly decreased to 68.8 % until the end of follow-up. In contrast, DFS for those aged 55–64 years showed a marginal decrease, reaching 97.4 % after 13 years. Competing-risks regression showed that individuals aged ≥ 75 and 65–74 had a significantly higher risk of dementia compared to those aged 55–64 years. Having more comorbidities at diabetes onset and initial treatment with ≥ 2 antidiabetics were clinical predictors. Conclusions: Later age at onset of diabetes is strongly associated with dementia. A better understanding of the diabetes–dementia relationship is needed to inform strategies for promoting specific healthcare pathways.