Trends in dementia incidence and mortality, and dynamic changes in comorbidity and healthcare utilization from 2004–2017: a Taiwan national cohort study

•The incidence of dementia increased slightly but the number of cases increased sharply•A Higher likelihood of multimorbidity after being diagnosed with dementia than before•Dementia cases had increased healthcare usage 1 year before diagnosis, which peaked 1 year afterward•Usage of psychotropic agents increased over 3 years before diagnosis of dementia•The cumulative 5-year mortality was nearly 50% among all identified dementia cases•High annual mortality remained around 12% from years 2 to 5