A Surprising Decline in the Incidence of Dementia

Editorial to accompany the article: Decline in Incidence and Prevalence of Dementia: An Analysis of Outpatient Claims Data by Bernhard Michalowsky et al. on the following pages

The incidence of dementia in persons older than 65 years fell by 25.7% in 2022 compared with 2015. Furthermore, the relative prevalence fell by 18.4%. This is the result of an analysis by Michalowsky et al. on dementia diagnoses based on outpatient claims data from statutory health insurers (1)—which cover 88% of the population.

The analysis found an absolute reduction in documented cases of dementia in Germany by 8.4%, from 1.56 million in 2015 to 1.43 million in 2022 (1). Even though a decline in the age-related incidence has been observed in many industrialized countries, the general assumption is that the absolute prevalence of dementia is rising because of demographic trends (2). These findings are therefore surprising and unexpected.

The role of modifiable risk factors

A possible reason for the decline in the incidence is a reduction in risk factors for dementia at the population level. The Lancet Commission concluded on the basis of its recent meta-analysis that up to 45% of all dementias are caused by potentially modifiable risk factors (3). Risk reducing effects in recent decades were probably the result of

• Higher educational attainment on average, associated with cognitively more demanding occupations
• Improved treatment options for hypertension, diabetes mellitus, and hypercholesterolemia, but also for hearing and visual impairments.

Other observed factors—at least in parts of the population—are

• An increase in physical activity or exercise
• A healthier diet, and
• A reduction in alcohol and tobacco consumption.

The occurrence of depression, head injuries, and social isolation as risk factors for dementia are unlikely to have been notably influenced. The newly identified risk factor environmental pollution is hard to assess in view of its temporal dynamic over recent decades.

A speculative aspect that has barely been studied and not confirmed is the continuous decline in persons who in their early lives experienced the second world war and the immediate postwar period and who bore partly serious physical and psychological stressors. The possible importance of this historical aspect was, for example, investigated in a recent meta-analysis that identified post-traumatic stress as a risk factor for dementia (4).

Effect of coding behavior?

The article by Michalowsky et al. is based on coded diagnoses from general and specialist practices. An alternative or complementary explanation for the data therefore lies in changed diagnostic or coding behavior among doctors—something the authors discussed in their article. Possible reasons include aspects of reimbursement issues or a lower diagnostic sensitivity in growing patient numbers and staff shortages in the practices. At the same time, an increase in documented cognitive testing methods was observed, which contradicts a decrease in diagnostic testing. Ultimately, only analyses of epidemiological data from representative cohorts can determine whether the numbers are falsely low as a result of coding effects.

Increases in mild cognitive impairment

A crucial secondary finding of the study is the increase in the diagnoses of mild cognitive impairment by 61.6% from 187 000 cases in 2015 to 302 000 cases in 2022. Since there are more people with an incident mild cognitive impairment than people with incident dementia, the numbers continue to show underdiagnosis but also growing openness to such diagnoses, which are likely to originate mainly in specialist practices or memory outpatient clinicals and are then included in the documentation of primary care doctors.

This finding is important since the future antibody treatments against amyloid pathology to treat Alzheimer’s disease have to be administered at the stage of mild cognitive impairment or very early dementia in order to be effective. The S3 guideline on dementias has already included the concept of Alzheimer diagnostics at the stage of mild cognitive disorders. ICD-11 introduces the diagnosis of mild neurocognitive impairment, which corresponds to the concept of mild cognitive impairment, with the option of coding Alzheimer’s disease as the cause (5, 6).

Better funding and support for prevention

Even though the decline in the incidence and prevalence of dementia is to be welcomed, the condition is still very common and is likely to gain in importance when the baby boomer generation reaches the vulnerable age (7).

Simultaneously, the data hint at the effectiveness of preventive measures and a healthy lifestyle for the brain, too. An increasing focus should therefore be placed on prevention to maintain cognitive abilities, combined with adapting the healthcare structures and processes to the incipient new era of biomarker based early diagnostics and molecular specific treatment of dementia.

Conflict of interest statement
The author declares that no conflict of interest exists.

Manuscript received on 26 May 2025, revised version accepted on 26 May 2025.

Translated from the original German by Birte Twisselmann, PhD.

Corresponding author
Prof. Dr. med. Frank Jessen

Cite this as
Jessen F: A surprising decline in the incidence of dementia.

Dtsch Arztebl Int 2025; 122: 371–2.
DOI: 10.3238/arztebl.m2025.0100

References

1. Michalowsky B, Hoffmann W, Riedel-Heller S, Kohring C, Teipel S, Akmatov M, Bohlken J, Holstiege J: Decline in incidence and prevalence of dementia : An analysis of outpatient claims data. Dtsch Arztebl Int 2025; 122: 373–8. DOI: 10.3238/arztebl.m2025.0090

2. Mukadam N, Wolters FJ, Walsh S, et al.: Changes in 21 prevalence and incidence of dementia and risk factors for dementia: An analysis from cohort studies. Lancet Public Health 2024; 9: e443-e60.

3. Livingston G, Huntley J, Liu KY, et al.: Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet 2024; 404: 572–628

4. Günak MM, Billings J, Carratu E, Marchant NL, Favarato G, Orgeta V: Post-traumatic stress disorder as a risk factor for dementia: Systematic review and meta-analysis. Br J Psychiatry 2020; 217: 600–8.

5. DGPPN, DGN: S3-Leitlinie Demenzen AWMF-Rg. Nr. 038–013 . 2023 .

6. www.bfarm.de/DE/Kodiersysteme/Klassifikationen/ICD/ICD-11/uebersetzung/_node.html (last accessed on 6 June 2025).

7. Beerheide, R et al.: Demografischer Wandel: Zeit für die Vorbereitung auf mehr Ältere drängt. Dtsch Aerztebl 2025; 122: A 561–4 .