Dementia Population Projections Revised in Light of New Evidence

Two large-scale epidemiological studies published this month in The Lancet suggest that dementia rates may be declining as a result of healthier and more educated populations. The Danish study compared two groups: the first born in 1905 and assessed at age 93 and the second born in 1915 and assessed at age 95. Despite the fact that they were two years older at the time of assessment, 23% of the 1915 cohort obtained maximum scores on the mini-mental state exam as opposed to 13% in the 1905 cohort.

In the U.K., an update of the Cognitive Function and Ageing Study (CFAS-2) found that the current prevalence of dementia in the 65 and older population was 6.5% or 1.8% lower than the 8.3% found when the study was last fielded in the early 1990s. Notably, both rates are substantially lower than the 13% over 65 prevalence rate reported by the U.S. Alzheimer’s Association (a figure that excludes non-Alzheimer’s types of dementia).

Both studies are great news for patients and health systems but, as is well-known, the populations of developed countries are aging rapidly: between 2010 and 2030, for example, the over 65 group will increase from 13.1% to 20.1% of the population in the U.S. and from 16.3% to 22.4% in Europe. In other words, dementia prevalence rate might be falling (or at least lower than previously thought) but the absolute number of people over 65 is growing.

To estimate the future burden of care (as well as the potential patient base for Alzheimer’s therapies), following are 20-year projections that account for both prevalence rates and the number of elderly persons in the U.S., Europe, and other developed countries. Population data is from the United Nations and prevalence rates are based on three scenarios. Note that these projections assume that the rate of dementia is the same across all developed countries and we are ignoring the distinction between Alzheimer’s and other forms of dementia (but since Alzheimer’s makes up the vast majority of age-related dementia, the figures below are sufficient for current purposes).

The three scenarios are as follows:

  1. The U.S. Alzheimer’s Association prevalence rates are correct and stable: i.e. the prevalence of dementia among people over 65 is 13.1% and will remain steady through 2030.
  2. The CFAS-2 prevalence rates are correct and stable: i.e. the dementia rate in this age group is actually 6.5% and this will be unchanged through 2030.
  3. The U.S. Alzheimer’s Association rates are correct but, as suggested by comparison of CFAS-1 and CFAS-2, prevalence is declining at 0.1% annually.

Dementia Population Projections: U.S., Europe, Other Developed Countries (2010 to 2030; in 000)

Scenario

Region

2010

2015

2020

2025

2030

Scenario 1

United States

5,303

6,200

7,272

8,466

9,499

 

Europe

15,727

16,740

18,244

19,824

21,436

 

Other Developed

4,897

5,660

6,191

6,531

6,853

 

Total

25,927

28,601

31,708

34,821

37,788

Scenario 2

United States

2,652

3,100

3,636

4,233

4,749

 

Europe

7,863

8,370

9,122

9,912

10,718

 

Other Developed

2,448

2,830

3,095

3,266

3,426

 

Total

12,963

14,300

15,854

17,411

18,894

Scenario 3

United States

5,303

5,962

6,713

7,489

8,038

 

Europe

15,727

16,097

16,841

17,537

18,138

 

Other Developed

4,897

5,443

5,715

5,778

5,799

 

Total

25,927

27,501

29,269

30,803

31,974

 

A RAND Corporation study published in the April 4, 2013 issue of the New England Journal of Medicine found that the excess cost of care for U.S. dementia patients averages $33,329 annually, so if there are fewer dementia patients, or if rates are declining, it will certainly bring relief to health budgets already strained by other diseases of aging.

PhRMA reports that, as of 2012, there were approximately 80 drugs in the pipeline for Alzheimer’s and 20 for other forms of dementia (the number may have declined somewhat due to some high profile failures). In any case, when we consider that the Alzheimer’s global disease burden increased by 99% between 1990 and 2010 and that only a handful of marginally effective therapies have been approved for the disease, the potential market for medicines to address this unmet need is huge even though the patient base may be smaller than previously thought.


Todd Clark
Todd Clark

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