Background
Methods
Results
Dementia prevalence
Study, setting, age range | Outcomes | Relative change (%) | Period | Interval (years) | Relative change (%) per year | Other findings/notes |
---|---|---|---|---|---|---|
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. |
Dementia incidence
Study, setting, age range | Outcomes | Relative change (%) | Period | Interval between incidence cohorts (years) | Relative change (%) per year | Other findings |
---|---|---|---|---|---|---|
Directly observed | ||||||
1. Indianapolis, IN, USA, African Americans, 65 years and older [36] | Dementia (DSM-III-R) AD | Dementia 3.6 % per annum (3.2–4.1 %) vs. 1.4 % per annum (1.2–1.7 %) 61 % reduction AD 2.5 % per annum (2.1–2.9 %) vs. 1.3 % per annum (1.0–1.5 %) 48 % reduction | 1991–2002 | 11 years | Dementia −5.5 % AD −4.4 % | Biggest reduction in youngest age groups. See also notes for study 4 in Table 1. |
2. Framingham, MA, USA, 60 years and older [37] | Dementia DSM-IV AD (NINCDS-ADRDA) VaD (NINDS-AIREN); diagnoses by consensus review panel | Dementia 44 % reduction AHR 0.56 (0.41–0.77) AD 30 % reduction AHR 0.70 (0.48–1.03) VaD 55 % reduction AHR 0.45 (0.23–0.87) | 1980–2006 | 26 years | Dementia −1.7 % AD −1.2 % VaD −2.1 % | Biggest reduction in youngest age groups. No reduction among the least educated. Significant improvements in education status; use of antihypertensive and statin medication; blood pressure and HDL levels; and prevalence of smoking, heart disease and stroke; however, prevalence of obesity and diabetes increased. |
3. Bordeaux, France, 65 years and older [38] |
Algorithm diagnosis (using MMSE score and IADL only)
Clinical diagnosis ‘based upon’ DSM-IIIR/DSM-V |
Algorithmic diagnosis
Overall AHR 0.65 (0.53–0.81) Women AHR 0.62 (0.48–0.80) Men AHR 1.10 (0.69–1.78)
Clinical diagnosis
Overall 0.92 (0.73–1.15) Women 0.90 (0.69–1.17) Men 1.21 (0.76–1.93). | 1988/1989–1998/1999 and 1999/2001– 2009/2010 | 10 years | Overall −3.5 % Women −3.8 % | Compared with the earlier cohort, the later cohort had more education, a higher BMI, a lower prevalence of stroke, and were less likely to be a current and more likely to be former smokers. More use of antihypertensive and lipid-lowering drugs. At baseline, they were less disabled on the 4-item IADL score and had higher MMSE scores. Differences in education, vascular factors and depression accounted only to some extent for this reduction (overall AHR 0.77, 95 % CI 0.61–0.97; women AHR 0.73, 95 % CI 0.57–0.95). |
4. Rotterdam, the Netherlands, 60–90 years [39] | Dementia (DSM-III-R) | Non-significant 25 % reduction RR 0.75 (0.56–1.02) | 1990–2000 | 10 years | −2.5 % | Hypertension, diabetes and obesity increased. Higher education. More diabetes treatment, more anti-thrombotics and much more statins. More past but less current smoking. Substantial reduction in overall mortality: HR 0.63 (0.52–0.77). |
5. Germany, insurance claims data, 65 years and older [40] | Dementia (ICD-10), or using cholinesterase inhibitors or memantine | 9 % reduction Men 0.91 (0.85–0.97) Women 0.91 (0.87–0.95) | 2004–2007/2007–2010 | 3 years | −3.0 % | 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 codes. For the analysis of incidence, two independent age-stratified samples were taken, the first comprising 139,617 persons in 2004 with follow-up until 2007, the second with 134,653 persons in 2007 with follow-up until 2010. Secular trends in clinical diagnosis or help-seeking cannot be excluded. |
6. Ontario, Canada; health insurance plan, hospital discharge and ambulatory care register; age range not reported [41] | Dementia diagnosis (ICD-9 or ICD-10) or cholinesterase inhibitor prescription | 7.4 % reduction; statistical significance of trend not reported | 2002–2013 | 12 years | −0.6 % | This study used claims data of the single state-provided insurance plan and comprehensive hospital admission, ambulatory care and drug prescription databases. Annual incidence rates, age- and sex-standardised, are reported for each year between 2002 and 2013. The trend is not linear, and statistical significance is not reported. Secular trends in clinical diagnosis or help-seeking cannot be excluded. |
7. Chicago, IL, USA [31] | AD | Stable OR 0.97 (0.90–1.04) | 1997–2008 | 11 years | No trend | |
8. Ibadan, Nigeria [52] | Dementia (DSM-III-R) AD | Stable Dementia 1.7 % per annum (1.4–2.0 %) vs. 1.4 % per annum (1.1–1.6 %) AD 1.5 % per annum (1.2–1.8 %) vs. 1.0 % (0.7–1.2 %) | 1991–2002 | 11 years | No trend | |
Inferred | ||||||
9. Stockholm, Sweden, 75 years and older [29] | Dementia (DSM-III-R) | Reduced incidence inferred from stable prevalence but increased survival with dementia | 1988–2002 | 14 years | Not reported | See also notes for Table 1, study 5. |
Dementia mortality
Study, setting, age range | Outcomes | Change in mortality and/or mortality hazard ratio | Period | Interval (years) | Other findings/notes |
---|---|---|---|---|---|
Directly observed | |||||
1. United States, HRS [21] | Mortality hazard ratio | Non-significant increase, from HR 2.53 to 3.11, p = 0.09 | 1993–2002 | 9 years | No report of absolute mortality rates, stratified or unstratified. However, given a presumed decline in overall mortality, it seems likely that mortality also declined among people with dementia, but to a slightly lesser extent |
2. Stockholm, Sweden [29] | Mortality hazard ratio | Stable HR: 2.42 (2.03–2.87) vs. 2.47 (2.03–3.00) | 1988–2002 | 14 years | Secular trend similar (30 % reduction in mortality) to that for those with no dementia, and for both sexes |
Mortality rate among people with dementia | 29 % reduction in mortality (HR 0.71, 95 % CI 0.57–0.88) adjusted for age, sex, education and MMSE score | ||||
3. Germany, insurance claims data, 65 years and older [32] | Mortality rate among people with dementia | 20 % increase in mortality among women with dementia (p < 0.0001) Non-significant 11 % increase in mortality among men with dementia (p = 0.75) | 2004–2007 | 3 years | Mortality among women without dementia remained constant over the two cohorts, while there was a non-significant 4 % decline in mortality rates among men without dementia. These findings would suggest an increase in the mortality hazard ratio associated with dementia, greater for women than for men. |
Inferred | |||||
Dementia duration | 1991–2002 | 11 years | Extrapolation from reported prevalence and incidence rates at the two time points suggests that survival time with dementia is 2.4 times longer for the second cohort. |
Secular trends within regions estimated from meta-analyses of individual studies
Discussion
Potential for prevention
The important impact of survival with dementia
Implications for future research
Conclusions
The projections of the ADI report for 2050 are alarming, but it is important to bear in mind that they are just that – projections.... The opportunity is here to ensure that the grim outlook for dementia in 2050, especially in low-income and middle-income countries, becomes nothing more than a work of fiction.