Alzheimer's disease and other forms of dementia

Alzheimer's disease and other forms of dementia are the most common neurodegenerative diseases. They are a major cause of loss of independence.

Our missions

  • Conduct epidemiological surveillance of Alzheimer’s disease and other forms of dementia: prevalence, incidence, trends over time, and geographic distribution

  • Providing information to public authorities and healthcare professionals

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Data

A prevalence that increases with age

In France, the PAQUID2 cohort study conducted in Gironde is a benchmark in the field of dementia epidemiology due to the significant duration of its follow-up and the diagnostic procedure implemented, with all cases confirmed by a neurologist. Based on projections for the entire French territory, this study estimated that approximately 1,000,000 people over the age of 65 were living with dementia in France in 2010; based on projections made under the assumption of a constant annual incidence (i.e., a constant number of new cases each year), the expected number of cases in 2030 would be approximately 1,750,000.

A possible decline in the incidence of dementia

Recent international studies suggest that the incidence of dementia may be slowly declining3.” Improvements in educational attainment and the management of vascular risk factors are the most frequently cited explanations4, 5. In France, data from two general population cohorts, PAQUID and Trois-Cités6, show a significant decrease in the incidence of dementia between the 1990s and 2000s, but only among women. It is possible that women, starting from a much lower level of education than men at the beginning of the 20th century, benefited more significantly from the impact of the general improvement in educational attainment on the decline in dementia.

The PAQUID and Trois-Cités cohorts are now outdated and can no longer be used to produce indicators of dementia prevalence in France. New surveillance tools must be developed. Data from the National Health Data System (SNDS1) are increasingly used for the surveillance of chronic diseases and represent a potential tool for the surveillance of dementia7.

In this context, an algorithm for identifying people with dementia was developed by Santé publique France using data on care provided under the Long-Term Condition (ALD) designation “Alzheimer’s Disease and Other Dementias,” reimbursement for anti-dementia medications, and hospital admissions:

  • 525,000 people aged 40 and older were identified as having dementia among beneficiaries of the general Social Security system living as of December 31, 2014;

  • The prevalence rate of 22 per 1,000 inhabitants increases sharply with age, rising from 2‰ among those aged 40–64 to 60‰ in older age groups;

  • The prevalence rate is nearly twice as high among women (29 per 1,000) compared to men (15 per 1,000).

When this number of cases covered by the general Social Security system is applied to the entire French population in the same age group, the number of people receiving care for dementia in France in 2014 is estimated at approximately 770,000 (68.7% of whom are women).

*Standardized by age and sex for the entire population and within age groups (40–64 years and ≥65 years); standardized by age separately for women and men.

 

 

≥40 years

 

 

40–64 years

 

 

≥65 years

 

 

 

Men

 

 

Women

 

 

Total

 

 

Men

 

 

Women

 

 

Set

 

 

Men

 

 

Women

 

 

Total

 

Standardized rates, general scheme (‰)*

15

29

22

2

1

2

43

73

60

Estimated number of cases, France as a whole

241,500

528,500

770,000

19,500

15,000

34,500

222,000

513,500

735,500

The number of people with dementia is underestimated in the SNDS1

These data should be interpreted with caution. Indeed, the criteria used to identify treated cases do not allow for the identification of all patients. Population-based cohort studies show that not all people with dementia are treated by the healthcare system. Indeed:

  • they are not always diagnosed, particularly among the very elderly;

  • not all are treated with medications whose efficacy has not been demonstrated and which are not always well tolerated.

Thus, the number of people with dementia is underestimated based on SNDS1 data. A comparison of estimates derived from SNDS1 with results from French and European population studies shows that, for younger individuals, the estimates obtained in SNDS1 are satisfactory. The underestimation applies to older individuals, with the prevalence of treated cases being on average 1.6 times lower than what would be expected in the general population according to the PAQUID cohort study.
By supplementing the PAQUID study’s projections with SNDS1 estimates for those aged 40–64, it is possible to estimate that approximately 1,200,000 people were living with dementia in France in 2014.

Mortality among people with dementia

In France, in 2006, there were nearly 46,000 death certificates listing dementia as the cause of death.8 These are the most recent available analyses regarding mortality. Among those who died with dementia:

  • 70% were women,

  • The average age at death was 85.9 years.

Deaths citing dementia accounted for 10.3% of deaths among people aged 60 and older (7% among men and 13.5% among women).

Among those who died with dementia listed as the cause, the three most common categories of causes of death were:

  • diseases of the circulatory system (40.5%),

  • invasive tumors (11.9%),

  • endocrine disorders (8.5%).

Deaths due to falls accounted for 2.4% of deaths with a diagnosis of dementia, representing a risk of death twice as high as among deaths without a diagnosis of dementia.

A higher prevalence of dementia among men than among women

Little data is currently available regarding the prevalence of dementia among young people in France, even though, among those under 65, the individual and societal consequences of this disease are dramatic. Similarly, the role of comorbidities in the onset of dementia among young people remains a poorly documented topic.

Preliminary studies conducted using the National Health Data System (SNDS) had shown that while the prevalence rates of dementia measured from these data significantly underestimate the expected prevalence among older adults, they are consistent with the expected data for individuals under 65 years of age9.

In France, the number of prevalent and incident cases of dementia was estimated at 24,000 and 5,300 in 2016. Prevalence and incidence rates increased with age and were higher among men than among women (33% and 39%, respectively).

Cardiovascular, neurological, and psychiatric diseases, as well as traumatic brain injuries, are major risk factors for dementia in young people. Since these conditions are more common in men, they account for 55% of the difference in incidence between the two sexes.

These are the first French estimates of the prevalence of dementia among people under the age of 65. Our research also shows how certain comorbidities contribute to the observed differences in incidence between men and women. These differences warrant further study to clarify the role of risk factors and comorbidities associated with gender, as well as differences in access to healthcare.

  1. National Health Data System (SNDS): a medical-administrative database containing healthcare services covered by the National Health Insurance (doctor visits and medical procedures, medications, hospitalizations, etc.), medical causes of death, and a sample of data from supplemental health insurance providers. The data are linked while ensuring the anonymity of individuals.

  2. Dartigues JF, Gagnon M, Michel P, Letenneur L, Commenges D, Barberger-Gateau P, et al. [The Paquid research program on the epidemiology of dementia. Methods and initial results]. Revue neurologique. 1991;147(3):225-30.

  3. Wu YT, Fratiglioni L, Matthews FE, Lobo A, Breteler MM, Skoog I, et al. Dementia in Western Europe: epidemiological evidence and implications for policy making. The Lancet Neurology. 2016;15(1):116-24.

  4. Larson, E.B., K. Yaffe, and K.M. Langa, New insights into the dementia epidemic. N Engl J Med, 2013. 369(24): pp. 2275-7.

  5. Norton, S., et al., Potential for primary prevention of Alzheimer's disease: an analysis of population-based data. Lancet Neurol, 2014. 13(8): p. 788-94.

  6. 3C Study Group. Vascular factors and risk of dementia: design of the Three-City Study and baseline characteristics of the study population. Neuroepidemiology. 2003;22(6):316-

  7. Gallini A, Moisan F, Maura G, Carcaillon-Bentata L, Leray E, Haesebaert J, et al. Identification of neurodegenerative diseases in administrative databases in France: A systematic review of the literature. Rev Epidemiol Sante Publique. 2017.

  8. Brosselin P, Duport N, Bloch J. Mortality with Alzheimer's disease and dementia in France, 2006. Revue d'Épidémiologie et de Santé Publique, 2010, 58(4): 269-276.

  9. Carcaillon-Bentata L, Quintin C, Moutengou E, Boussac-Zarebska M, Moisan F, Ha C, Elbaz A. Can the prevalence of Alzheimer’s disease and other dementias be estimated using medical-administrative databases? Comparison with population-based cohort data. Bull Epidemiol Hebd 2016;(28-29):459-67.