Generational Differences in Age-Specific Dementia Prevalence Rates.

Importance: Dementia is a significant public health challenge, with its prevalence expected to increase as life expectancy continues to extend globally. Objective: To estimate generational differences in age-specific dementia prevalence across the US, Europe, and England. Design, Setting, and Participants: This cross-sectional study used data from 1994 to 2021 from the United States Health and Retirement Study (HRS), from 2004 to 2020 from the Survey of Health, Ageing and Retirement in Europe (SHARE), and from 2002 to 2019 from the English Longitudinal Study of Ageing (ELSA). Statistical analysis was performed from May 2023 to February 2025. Main Outcomes and Measures: First, 2 different methods-the validated algorithm and machine learning techniques as the robustness check-were used to identify respondents with probable dementia. Then the status of dementia was used to estimate the association of cohort with dementia status by age-period-cohort methodology. Results: Of the 99 420 individuals (mean [SD] age, 79.1 [6.2] years; 59.2% women) in the HRS dataset, 21 069 (21.2%) were included in this study; of the 83 580 individuals (mean [SD] age, 78.6 [5.9] years; 54.7% women) in the SHARE dataset, 32 490 (38.9%) were included in this study; and of the 31 384 individuals (mean [SD] age, 77.9 [5.6] years; 55.8% women) in the ELSA dataset, 8878 (28.3%) were included in this study. Focusing on people aged 71 years or older and controlling for age and period effects, birth cohorts born more recently were less likely to develop dementia in all 3 regions, albeit at different rates (point estimate for 1944-1948 vs 1919-1923 cohorts: US, -0.55 [95% CI, -0.77 to -0.34] vs -0.18 [95% CI, -0.25 to -0.10]; Europe, -1.49 [95% CI, -1.72 to -1.27] vs -0.24 [95% CI, -0.35 to -0.13]; and England, -0.48 [95% CI, -0.89 to -0.08] vs -0.23 [95% CI, -0.38 to -0.07]). This decreasing trend was more pronounced among women than men (point estimate in 1944-1948 for women vs men: US, -0.55 [95% CI, -0.86 to -0.30] vs -0.48 [95% CI, -0.84 to -0.13]; Europe, -1.50 [95% CI, -1.80 to -1.21] vs -1.34 [95% CI, -1.70 to -0.99]; and England, -0.76 [95% CI, -1.30 to -0.23] vs -0.07 [95% CI, -0.69 to 0.54]); the point estimates for men in England were not statistically significant. Conclusions and Relevance: In this cross-sectional study examining generational differences in age-specific dementia prevalence across the US, Europe, and England, we found that individuals from more recent birth cohorts had lower proportions of people with dementia. Work of this kind is relevant to plan for health and long-term care policy and workforce requirements across these regions now and into the future.