World-wide variations in tests of cognition and activities of daily living in participants of six international randomized controlled trials

•Cognitive and functional test scores in randomized controlled clinical trial cohorts vary widely across world regions.•The difference in cognitive test performance was large in comparison to difference in measures of activities of daily living (ADLs). Accounting for country-level factors reduced the differences between world regions in estimates of cognitive impairment.•Functional test measures were less variable than cognitive test measures and so tests focusing on activities of daily living could be used to better estimate dementia prevalence in international studies.