One in five people will develop dementia at some point in their life. Scientists are still in the dark about what the possible causes are. New research points to a beneficial effect of the flu vaccine.

Of the people studied, those who received a flu vaccine were 40 percent less likely to develop Alzheimer’s over four years than those who had not been vaccinated against influenza. The researchers at UTHealth Houston compared more than 900,000 Americans over the age of 65 who received a flu shot with a group of approximately the same size and age who did not receive the shot. “We found that flu vaccination in older adults reduces the risk of Alzheimer’s disease for several years. This effect became stronger the longer people had received a flu shot each year. In other words, Alzheimer’s disease was least prevalent among those who consistently received the flu vaccine each year,” said study leader Avram S. Bukhbinder. “Future research should show whether the flu shot also influences the progression of the disease in patients with Alzheimer’s.”

Two years ago, the same researchers also found a link between the development of Alzheimer’s and the flu shot. In this new study, they took a much larger sample. And that confirmed previous results. At a follow-up appointment four years later, more than 5 percent of participants who received a flu shot were found to have Alzheimer’s. In the non-vaccinated people, that percentage was 8.5 percent. That’s a huge difference. These results underline the strong protective effect of the flu vaccine against Alzheimer’s disease, Bukhbinder said. Further research is needed to find explanations for this surprising result.

Elderly lady gets flu shot. Photo: Getty Images

“There are indications that other vaccines can also protect against Alzheimer’s. So we don’t think this is a specific effect of the flu vaccine,” says professor of neurodegenerative disorders Paul. E. Schulz. “The immune system is complex and we think that some changes, from pneumonia for example, can activate it in a way that makes Alzheimer’s worse. But other things like a vaccine can actually activate the immune system so that it protects against Alzheimer’s.”

Previous studies have also found a reduced risk of dementia after vaccinations against, for example, tetanus, polio and herpes. Bukhbinder thinks it is worth investigating whether there is such a link between a corona jab and a lower risk of Alzheimer’s.

Figures on dementia

Due to the aging population, the number of people with dementia will double from 290,000 to more than half a million in 2040. One in three women and one in seven men will develop dementia at some point in their life. Alzheimer’s disease is involved in 70 percent of the cases. People with dementia live an average of 6.5 years with the disease. Two thirds of the informal caregivers indicated that the diagnosis was made after more than a year. Dementia is really a disease of old age, yet there are an estimated 15,000 patients in the Netherlands younger than 65 years.

Seven lifestyle factors are mentioned that increase the risk of dementia: low mental activity, for example little challenge in work, hobbies or social contact, smoking, little exercise, depression, high blood pressure, diabetes and serious overweight from middle age. Hearing impairment is often cited as a cause of dementia, but the link has not yet been proven. It may be that people are less socially active and their brains stimulate less because they have poor hearing, which makes them more likely to become demented. It is also possible that the hearing center in the brain is one of the first parts of the brain to be affected by the disease or that hearing impairment happens to occur in the period before someone gets dementia. After all, it is also an old age ailment.