10% of those over 70 have Alzheimer’s but do not yet have symptoms

30% of people over 70 years of age have Alzheimer’sbut a third of them have not yet developed any symptoms of the disease and another third have incipient symptoms and possibly have not yet been diagnosed, according to the first research that has evaluated the prevalence of Alzheimer’s in a general population.

The results, which are presented today in the journal Nature, imply that 11% of people over 70 years of age are candidates to be treated with the new antibodies against the beta-amyloid protein that slows the progression of the disease.

The research has been based on a new test that allows early diagnosis of Alzheimer’s with a blood test. This test, which is already beginning to be used in hospitals, analyzes the protein p-tau217, which comes from the brain and increases in the blood from the initial stages of Alzheimer’s.

Until now, a diagnosis of Alzheimer’s required invasive and expensive techniques. Photo: Unsplash

Until now, a diagnosis of Alzheimer’s required invasive and expensive techniques (a lumbar puncture or a PET technique neuroimaging), which prevented prevalence studies in a population without symptoms.

New drugs against Alzheimer’s are indicated for 11% of those over 70 years of age, according to researchers

Blood samples from 11,486 people in Norway have been analyzed, all of them participating in the Trondelag Health Studywhich started in 1984 and is still going. 78% of the samples were from people over 70 years old.

The results of the analyzes have been compared with clinical data of the study participants, which made it possible to evaluate whether they had symptoms of cognitive impairment or dementia.

Other variables relevant to Alzheimer’s have also been assessed, such as educational level, genetic profile o cardiovascular risk factors.

Only 33% of people with symptoms of mild cognitive impairment have Alzheimer’s. Photo: Unsplash

“It is an especially relevant study because it allows us to make a more precise estimate of the prevalence of Alzheimer’s” than previous studies that were not representative of the general population, the neurologist highlights Marc Suárez-Calvet, from the BarcelonaBeta Brain Research Center and the Hospital del Mar. But he warns that “it is a representative cohort of the Norwegian population and we will have to do similar studies in other countries, because perhaps the prevalence is different.”

According to results presented in Nature, only 33% of people with symptoms of mild cognitive impairment have Alzheimer’s. In the remaining 67% the cognitive impairment is due to other causes, so it does not have to progress towards disability and dementia. Still, the older the age at which cognitive decline occurs, the more likely it is due to Alzheimer’s.

Conversely, only two-thirds of people over 70 with Alzheimer’s have cognitive impairment or dementia. Also in this case, at an older agemore likely Alzheimer’s will cause symptoms.

“With the arrival of drugs capable of reducing beta-amyloid pathology and slow cognitive decline, accurate knowledge of the prevalence of Alzheimer’s disease is essential to predict the number of people candidates for treatment and estimate future demands on the healthcare system and associated costs,» they write. the authors of the research in Nature.

Europe has approved this year the first two antibodies that slow the progression of Alzheimer’s, lecanemab from Eisai and Biogen and donanemab from Eli Lilly. Neither of them is yet available in Spain, waiting for the Ministry of Health and the pharmaceutical companies to agree on prices. Neurologists hope to start prescribing them in 2026.

This year, Europe approved the first two antibodies that slow the progression of Alzheimer’s. Photo: Unsplash

Data from Norway confirms that the higher a person’s educational level, the more protected they are from Alzheimer’s. This protection is not only explained by cognitive resources to compensate the deterioration of the disease (the so-called cognitive reserve) but also seems to affect the biological process of neurodegeneration.

Thus, people with university studies have levels of p-tau217 lower than those with secondary education, and these have lower levels than those who only completed primary education.

The researchers warn that more studies are necessary to clarify the relationship between education and neuroprotection because they have not analyzed variables that may interfere such as smoking, sedentary lifestyle and alcohol consumption.

Research questions whether women are more vulnerable to Alzheimer’s than men. Photo: Unsplash

On the contrary, research questions whether women are more vulnerable to Alzheimer’s than men. With the Norwegian data, there are no differences between men and women in any age group if Alzheimer’s is diagnosed based on the level of the pTau217 protein in the blood.

Above 85 years of age, it has been observed that there are more cases of dementia in women and more mild cognitive impairment in men.

Joseph Corbella