In the base year 2015, there were 9 million people aged 75 years and above in Germany. At age 75, 7.4% of men and 7.7% of women were affected by dementia. This share increased steeply with age, and in the highest age group aged 89 years and above 30.8% of men and 40.0% of women had a dementia diagnosis.
According to the prevalences from the AOK data (Table 1), 5.37 million people of this age group had neither a diagnosis of diabetes nor a diagnosis of dementia (Diab−Dem−); 2.29 million people had been diagnosed with diabetes, but without dementia (Diab+Dem−); 0.87 million people had been diagnosed as dementia patients without diabetes (Diab−Dem+); and 0.46 million people had a diagnosis of diabetes and dementia (Diab+Dem+). In total, 1.34 million people had received a dementia diagnosis (with and without diabetes diagnosis) in 2015.
Estimated transition probabilities
Figure 2 shows the estimated age- and sex-specific transition probabilities for the first year 2015. At age 50, about 1.2% of men and 0.8% of women of state 1 (Diab−Dem−) received a diabetes diagnosis within one year. Probabilities increase with age up to age 72 for men (2.2%) and 76 for women (1.7%); thereafter the incidence of diabetes decreases for both sexes. For the transition from state 1 (Diab−Dem−) to state 3 (Diab−Dem+) we observed an exponential increase for men and women, with slightly higher rates for men than for women. At age 50, the probability to transit was 0.04% for men and 0.02% for women, at age 89 + it was 5.6% for men and 5.3% for women. The probability to experience the transition to diabetes and dementia within one quarter was very low (state 1 to state 4). From age 80 onwards this probability was around 0.1% for men and women.
Regarding the transition from state 2 (Diab+Dem−) to state 4 (Diab+Dem+), we observed an exponential increase for men and women, with slightly higher rates for men than for women until the age of 80. At age 50, the probability was 0.1%, and in the highest age group of 89 years and older, probabilities were 9.2% for men and 10.3% for women. At all ages, the dementia probability of persons with diabetes was higher than for persons without diabetes. For the transition from state 3 (Diab−Dem+) to state 4 (Diab+Dem+), we observed again a reverse U-shaped pattern with a probability of 4.4% for men at age 72, and 4.0% for women at age 76.
Estimated death rates
Death rates (Fig. 3) rise exponentially with age, and individuals without diabetes and dementia (Diab−Dem−) had the lowest death rates at all ages, followed by those with diabetes only (Diab+Dem−) and dementia only (Diab−Dem+). Patients with diabetes and dementia had the highest death rates. For example, at age 80, the death rate of men of state 1 (Diab−Dem−) was 0.04, men of state 2 (Diab+Dem−) had 0.05, men of state 3 (Diab−Dem+) had 0.14 and the death rate of men with diabetes and dementia (Diab+Dem+) was 0.16. For women, corresponding values were 0.02, 0.04, 0.10 and 0.12 (Fig. 3).
Results of multi-state projections
Modeling the demographic components of the future number of dementia patients reveals the overwhelming effect of future increases in life expectancy. Starting with 9 million individuals at ages 75 and above in 2015, the ageing of the baby boomer generation will lead to an increase of up to 10.89 million in 2040, even under the assumption of constant transition probabilities and death rates (Sc1, Table 1). Rising life expectancy, modeled by a relative annual reduction of death rates in all states by 2.5%, results in 13.45 million people (Sc2), which is comparable to the results of the 14th coordinated population projection of the Federal Statistical Office in Germany [26].
Under the assumption of constant transition probabilities and death rates (Sc1) there will be a growth in the absolute number of persons with dementia, from 1.34 million in 2015 to 1.72 million in 2040, corresponding to an increase of 29% compared to 2015. Thus, the ageing of the baby boomers alone will add about 380,000 dementia patients. Relative annual reductions of death rates by 2.5% will additionally add almost one million dementia patients, totaling up to 2.68 million affected persons in 2040 (Sc2, Table 1 and Fig. 4).
In the following, we use the projections for 2040 from Sc2 as reference values.
In Sc2.1 (Table 1, Fig. 4), the 1% relative annual reduction in diabetes incidence results in a reduced number of dementia cases with diabetes (Diab+Dem+: 1.50 million in Sc2.1–1.56 million in Sc2.2 = -60,000, -3.8%), while dementia cases without diabetes (Diab−Dem+) increase by + 3.0% (1.16 million in Sc2.1–1.13 million in Sc2 = + 34,000). This is because more people remain in state 1 under this assumption and thus are at risk of dementia. In sum, this strategy only slightly affects the future total number of dementia cases with 26,000 fewer cases (2.66 million in Sc2.1–2.68 million in Sc2= -26,000, -1.0%).
In Sc2.2, a relative reduction of 1% per year in the incidence of dementia in diabetes patients was assumed (Table 1, Fig. 4). This results in 1.38 million dementia cases with diabetes (Diab+Dem+: 1.38 million in Sc2.2–1.56 million in Sc2 = -175,000, -11.3%), while the trend in the number of dementia cases without diabetes (Diab−Dem+) remains unchanged. Overall, this strategy results in 175,000 fewer dementia cases (2.51 million in Sc2.2–2.68 million in Sc2 = -175,000, -6.5%).
Sc2.3 combines the two prevention strategies. Again, we observe a + 3.0% increase in dementia cases without diabetes (Diab−Dem+) (1.16 million in Sc2.3–1.13 million in Sc2 = + 34,000), but a 225,000 decrease in the number of individuals with both diagnoses to 1.33 million cases (Diab+Dem+: 1.33 million in Sc2.3–1.56 million in Sc2 = -225,000, -14.5%). Combining the two prevention strategies yields 2.49 million dementia cases (2.49 million in Sc2.3–2.68 million in Sc2 = -191,000, -7.1%).
In Sc2.4, a relative reduction of 1% per year in dementia incidence in persons without diabetes and dementia yields 0.96 million dementia cases without diabetes (Diab−Dem+: 0.96 million in Sc2.4–1.13 million in Sc2 = -170,000, -15.0%) and 1.53 million dementia cases with diabetes (Diab+Dem+: 1.53 million in Sc2.4–1.56 million in Sc2 = -30,000, -1.5). Overall, general unspecific dementia prevention strategies result in 2.49 million dementia cases in 2040 (2.49 million in Sc2.4–2.68 million in Sc2 = -193,000, -7.2%).
Table 1
Results of multi-state projection, estimated number of persons by state in Germany aged 75 + in 2040
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Projected number by state in million
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Year
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Scenario
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Assumptions
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Total
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Diab−Dem−
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Diab+Dem−
|
Diab−Dem+
|
Diab+Dem+
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Total dementia cases
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Total diabetes cases
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Change in Diab−Dem+ cases compared to Scenario 2
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Change in Diab+Dem+ cases compared to Scenario 2
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Change in total demetia cases compared to Scenario 2
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2015
|
Base year
|
|
9.00
|
5.37
|
2.29
|
0.87
|
0.46
|
1.34
|
2.75
|
|
|
|
2040
|
Scenario 1
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Status quo
|
10.89
|
6.06
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3.12
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0.76
|
0.96
|
1.72
|
4.07
|
-
|
-
|
-
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Scenario 2
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Death rates by -2.5%
|
13.41
|
6.95
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3.78
|
1.13
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1.56
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2.68
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5.33
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-
|
-
|
-
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Scenario 2.1
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Death rates by -2.5%, diabetes incidence of Diab−Dem− by -1%
|
13.45
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7.30
|
3.49
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1.16
|
1.50
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2.66
|
4.99
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+ 3.0%
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-3.8%
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-1.0%
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Scenario 2.2
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Death rates by -2.5%, dementia incidence of Diab+Dem− by -1%
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13.50
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6.95
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4.04
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1.13
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1.38
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2.51
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5.42
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0.0%
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-11.3%
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-6.5%
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Scenario 2.3
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Death rates by -2.5%, diabetes incidence of Diab−Dem− by -1%, dementia incidence of Diab+Dem− by -1%
|
13.54
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7.30
|
3.74
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1.16
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1.33
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2.49
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5.07
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+ 3.0%
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-14.5%
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-7.1%
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Scenario 2.4
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Death rates by -2.5%, dementia incidence of Diab−Dem− by -1%
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13.51
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7.22
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3.80
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0.96
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1.53
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2.49
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5.33
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-15.0%
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-1.5%
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-7.2%
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Note: Source: AOK 2014–2017 and HMD |