Methodological strengths and weakness of cohorts and administrative data for developing population estimates of dementia

There are three main methods of obtaining population data on the incidence and/or prevalence of dementia: cross‐sectional surveys (which may be repeated over time); cohort studies that follow people initially without dementia and count newly diagnosed cases over time; and administrative health records (including linkage of records from multiple sources). The major challenges for all these methods are: how well the study sample represents the target population, the accuracy of diagnoses, and the costs of maintaining the data collection over time.