Global variation in tests of cognitive and physical function: analysis of six international randomized controlled trials
Bibliographic record
Abstract
Abstract Background Better understanding of global variation in simple tests of cognition and function would aid the delivery and interpretation of multi-national studies of the prevention of dementia and functional decline. Methods We aim to describe the variation in simple measures of cognition and function by world region, study, recruitment centre or individual level factors. In six RCTs that measured cognition with the mini-mental state examination (MMSE), Montreal cognitive assessment (MoCA), and instrumental activities of daily living (IADL) with the Standardised Assessment of Everyday Global Activities (SAGEA), we estimated average scores by global region with multilevel mixed-effects models. We estimated the proportion of participants with cognitive or functional impairment with previously defined thresholds (MMSE≤24 or MoCA≤25, SAGEA≥7), and with a country-standardised z-score threshold of cognitive or functional score of ≤-1. Results In 91,396 participants (mean age 66.6±7.8 years, 31% females) from seven world regions, all global regions differed significantly in estimated cognitive function (z-score differences 0.11–0.45, p<0.001) after accounting for individual-level factors, centre and study. In different regions, the proportion of trial participants with MMSE≤24 or MoCA≤25 ranged from 23–36%; the proportion below a country-standardised z-score threshold of ≤1 ranged from 10–14%. The differences in prevalence of impaired IADL (SAGEA≥7) ranged from 2–6% and by country-standardised thresholds from 3–6%. Conclusions Accounting for country-level factors reduced large differences between world regions in estimates of cognitive impairment. Measures of IADL were less variable across world regions, and could be used to better estimate dementia incidence in large studies. Impact statement We certify that this work is novel. After analysing data from a large cohort of participants with a history of cardiovascular disease or cardiovascular risk factors, who were recruited in six international randomised controlled trials (RCTs) we found that accounting for country-level factors reduced large differences between world regions in estimates of cognitive impairment, while measures of functional impairment were less variable across world regions. Key Points 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. Cognitive test measures were less variable and could be used to better estimate dementia incidence in international studies. Why this study matters? We found that cognitive and functional test scores in RCT cohorts varied widely across world regions. The difference in cognitive test performance was large in comparison to difference in measures of activities of daily living. The impact of differences on the performance of cognitive tests, which were developed in high-income countries, creates challenges for harmonized studies of cognitive decline prevention in different world regions. Future studies using the same test around the world could standardise cognitive score by country, and consider using in addition measures of instrumental and basic activities of daily living, where there is less variation across world regions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.107 | 0.181 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.014 | 0.022 |
| Bibliometrics | 0.003 | 0.005 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.005 | 0.004 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.004 | 0.004 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".