Table 1 Studies estimating changes in prevalence of dementia or Alzheimer’s disease over time

1. United Kingdom, MRC CFAS, 65 years and older [27]

Dementia (GMS-AGECAT)

30 % reduction AOR 0.7 (0.6–0.9)

1993–2011

18 years

−1.7 %

Bigger dementia prevalence reduction in older age groups. Reduction in the proportion of older people, and people with dementia living in care homes. Increased prevalence of dementia among care home residents.

2. Zaragoza, Spain, 65 years and older [28]

Dementia (DSM-IV)

Non–significant 25 % reduction AOR 0.75 (0.56–1.02) Women AOR 1.02 (0.69–1.51) Men AOR 0.40 (0.25–0.65)

1988–1995

7 years

−3.6 %

Bigger (and statistically significant) dementia prevalence reduction in men. No changes observed in education level.

3. HRS, nationally representative, United States, 70 years and older [21]

Moderate/severe cognitive impairment (probable dementia)

29 % reduction AOR 0.65 (0.58–0.73)

1993–2002

9 years

−3.2 %

Increases in levels of education, significantly fewer IADL limitations but higher rates of cardiovascular risk factors and cardiovascular disease, including diabetes, hypertension, obesity and heart disease. Education differences accounted for 43 % of the prevalence difference between time points. Residents of care homes were excluded from the 1993 wave. The 6.2 % of 2002 respondents who were residents of care homes were also excluded from the comparative analysis. This may have biased the comparison, if transition to care homes was reserved for those with more severe dementia at the later time point.

4. United States, Indianapolis, IN, African Americans, 65 years and older [31]

Dementia (DSM-III-R) AD

Stable 6.8 % vs. 7.5 % (dementia p = 0.35) 5.5 % vs. 6.8 % (AD p = 0.26)

1991–2002

11 years

No trend

Increases in levels of hypertension, diabetes and stroke, but also higher levels of treatment, consistent with national trends for African Americans over this time period. Some differences in recruitment procedures, and a higher refusal rate in 2002.

5. Stockholm, Sweden, 75 years and older [29]

Dementia (DSM-III-R)

Stable 17.5 % vs. 17.9 % AOR 0.85 (0.68–1.05)

1988–2002

14 years

No trend

Much higher levels of education at the second time point.

6. Germany, insurance claims data, 65 and older [32]

Dementia (ICD-10)

Stable prevalence in all age groups and both sexes, other than women aged 75–84 years AOR 0.97 (0.95–0.98)

2007–2009

3 years

−1.2 % (women aged 75–84 years)

This study used claims data of the largest public health insurance company in Germany. The data contained complete inpatient and outpatient diagnoses according to ICD-10. For the analysis of prevalence, age-specific prevalence was estimated for the years 2007, 2008 and 2009. Secular trends in clinical diagnosis or help-seeking cannot be excluded.

7. Goteborg, Sweden, aged 70 and 75 years [30]

Dementia historical criteria

Stable prevalence for both age groups Age 70 years M 1.7 % vs. 0.9 % F 2.2 % vs. 3.7 % Age 75 years M 6.8 % vs. 6.9 % F 3.8 % vs. 5.3 %

Aged 70 years 1976–2000 Aged 75 years 1976–2005

Aged 70 years 25 years Aged 75 years 30 years

No trend

Higher education level, better results on cognitive tests, better socioeconomic status, better treatment of vascular risk factors and better general physical health in the later-born cohorts

8. Umea, Sweden, 85 years and older [33]

Dementia (DSM-IV)

40 % increase (p = 0.001)

2001–2006

5 years

+8.0 %

Prevalence differences not adjusted for other covariates, but age distribution was similar. Increase in the prescription of antihypertensive and statin drugs, cholinesterase inhibitors, and more heart surgery.

9. Japan, Hisayama, aged 65 years and older [34]

Dementia, AD

38 % increase (dementia) AOR 1.34 (0.97–1.87) 255 % increase (AD) 3.28 (1.75–6.14)

1985–2005

20 years

+1.9 % (dementia) + 12.8 % (AD)

Ratio of AD/VaD increasing from 0.5 in 1985 to 1.4 in 2005.