The Cognitive Online Self-Test Amsterdam (COST-A): Establishing norm scores in a community-dwelling population

Alzheimers Dement (Amst). 2021 Sep 14;13(1):e12234. doi: 10.1002/dad2.12234. eCollection 2021.


Background: Heightened public awareness about Alzheimer's disease and dementia increases the need for at-home cognitive self-testing. We offered Cognitive Online Self-Test Amsterdam (COST-A) to independent groups of cognitively normal adults and investigated the robustness of a norm-score formula and cutoff.

Methods: Three thousand eighty-eight participants (mean age ± standard deviation = 61 ± 12 years, 70% female) completed COST-A and evaluated it. Demographically adjusted norm scores were the difference between expected COST-A scores, based on age, gender, and education, and actual scores. We applied the resulting norm-score formula to two independent cohorts.

Results: Participants evaluated COST-A to be of adequate difficulty and duration. Our norm-score formula was shown to be robust: ≈8% of participants in two cognitively normal cohorts had abnormal scores. A cutoff of -1.5 standard deviations proved optimal for distinguishing normal from impaired cognition.

Conclusion: With robust norm scores, COST-A is a promising new tool for research and clinical practice, providing low cost and minimally invasive remote assessment of cognitive functioning.

Keywords: Alzheimer's disease; cognition; normative data; remote assessment; screener; self‐testing.