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. 2020 Aug 4;95(5):e519-e531.
doi: 10.1212/WNL.0000000000010022. Epub 2020 Jul 1.

Twenty-seven-year time trends in dementia incidence in Europe and the United States: The Alzheimer Cohorts Consortium

Affiliations

Twenty-seven-year time trends in dementia incidence in Europe and the United States: The Alzheimer Cohorts Consortium

Frank J Wolters et al. Neurology. .

Abstract

Objective: To determine changes in the incidence of dementia between 1988 and 2015.

Methods: This analysis was performed in aggregated data from individuals >65 years of age in 7 population-based cohort studies in the United States and Europe from the Alzheimer Cohort Consortium. First, we calculated age- and sex-specific incidence rates for all-cause dementia, and then defined nonoverlapping 5-year epochs within each study to determine trends in incidence. Estimates of change per 10-year interval were pooled and results are presented combined and stratified by sex.

Results: Of 49,202 individuals, 4,253 (8.6%) developed dementia. The incidence rate of dementia increased with age, similarly for women and men, ranging from about 4 per 1,000 person-years in individuals aged 65-69 years to 65 per 1,000 person-years for those aged 85-89 years. The incidence rate of dementia declined by 13% per calendar decade (95% confidence interval [CI], 7%-19%), consistently across studies, and somewhat more pronouncedly in men than in women (24% [95% CI 14%-32%] vs 8% [0%-15%]).

Conclusion: The incidence rate of dementia in Europe and North America has declined by 13% per decade over the past 25 years, consistently across studies. Incidence is similar for men and women, although declines were somewhat more profound in men. These observations call for sustained efforts to finding the causes for this decline, as well as determining their validity in geographically and ethnically diverse populations.

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Figures

Figure 1
Figure 1. Incidence rates of dementia, stratified by cohort and age group
AGES–Reykjavik Study = Age, Gene/Environment Susceptibility–Reykjavik Study; CFAS = Cognitive Function and Ageing Studies; FHS = Framingham Heart Study; PAQUID = Personnes Agées QUID.
Figure 2
Figure 2. Incidence rates of dementia by age group, comparing men vs women
Figure 3
Figure 3. Trends in the incidence of dementia
The forest plots represent the incidence trend for (A) all-cause dementia, (B) Alzheimer disease, (C) all-cause dementia in men, and (D) all-cause dementia in women, expressed as a hazard ratio (HR) per 10-year advance in calendar time. This HR was calculated to compare temporal trends across studies, and can be interpreted as a change in the 5-year hazard per decade advance in calendar time. 3C = Three-City Study; CFAS = Cognitive Function and Ageing Studies; CI = confidence interval; FHS = Framingham Heart Study; RS = Rotterdam Study.
Figure 4
Figure 4. Projected incidence of dementia in millions
Projected yearly incidence of dementia on the basis of current rates (solid lines) and projected incidence of dementia assuming continuation of a decreasing trend (dashed lines). Current rates are based on estimates from the 2012 World Alzheimer Report, which at the time estimated that 682 million new cases would occur over the 2010 to 2050 period.

References

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