Trends in Memory Function and Memory Impairment Among Older Adults in the United States and Europe, 1996-2018.

Background: Single-country studies document varying time trends in memory function and impairment. Comparative analyses are limited.

Methods: We used self-respondent data on adults aged 50+ years in 13 countries from 3 surveys (United States: Health and Retirement Study, 1998-2018; England: English Longitudinal Study of Ageing, 2002-2018; 11 European countries: Survey of Health, Ageing and Retirement in Europe, 2004-2019). Memory is measured with tests of immediate and delayed word recall. Unweighted age- and gender-adjusted mixed effects regression models as well as models with adjustments for additional sociodemographic characteristics and health behaviors were examined. Heterogeneity in trends by gender, age group, and educational attainment was measured.

Results: The age-adjusted 10-year improvement in average test score is 0.04 standard deviations (SDs) (95% confidence interval [CI]: 0.03, 0.05) in the United States, 0.17 SDs (95% CI: 0.15, 0.19) in England, and 0.24 SDs (95% CI: 0.23, 0.25) in SHARE countries. Trends are largely similar across gender, age groups, and educational attainment. Regional differences in trends remain after adjustment for potential mechanisms. The difference between the United States and other countries is particularly large under 75 years of age compared to 75 years and older.

Conclusions: Pace of improvement in memory function varies strongly across countries. On average, the 11 European countries studied had the fastest improvement, followed by England. The trend in the United States indicates improvement, but at a much slower pace compared to that in England and other European countries. Uncovering the causes for the cross-country heterogeneity in time trends, and in particular the reasons for the comparatively poor performance of the United States, should be both a research and public health priority.