American researchers are behind the new study, published in the journal Lancet. They found that levels of phosphorylated tau, a protein linked to Alzheimer's disease, can increase as early as age 60.
The study examined the blood of 1,350 people without dementia, with an average age of 61. They were also asked to perform various cognitive tests.
Worse on tests
86 of the participants had elevated levels. They also performed worse on average on tests that measure the ability to plan, focus and take on new tasks. The tests were repeated every five years, and those who had elevated levels the first time around deteriorated more quickly than others.
Blood tests to identify the protein tau are already used in some regions as part of the diagnostics for Alzheimer's disease.
It is a simpler method than the spinal fluid tests and brain imaging used today, says Henrik Zetterberg, chief physician at Sahlgrenska University Hospital and professor of neurochemistry at the University of Gothenburg.
He has been involved in developing the blood test used in Sweden.
"We have seen that in 70-year-olds, about 10 percent have an elevation of these markers. Here we see that the process probably starts earlier," he says.
No treatment available
There are currently no approved drugs available in Sweden that target the changes that tau and another protein, beta-amyloid, can cause in the brain. However, development is underway at several pharmaceutical companies. Henrik Zetterberg believes that when more effective drugs with fewer side effects become available, early testing may be beneficial.
Most treatments will be most beneficial if they are started early. But at present there is no reason to test widely as it risks leading to unnecessary concern, he says.
This spring, the expert body NT Council recommended that healthcare providers not use the approved drug Leqembi. The council is also investigating whether or not another drug, Kinsunla, should be recommended.
Henrik Zetterberg has previously given lectures sponsored by companies that market both drugs.
Alzheimer's disease is the most common form of dementia. In Sweden, just over 100,000 people are affected.
A characteristic of the disease is that brain tissue is gradually destroyed.
The most important risk factors are old age and heredity. Lifestyle also has an impact.
The likelihood of being affected increases significantly after the age of 65.
According to studies, approximately 40 percent of disease cases can be traced to lifestyle factors. These include high blood pressure, diabetes and other metabolic diseases, as well as physical inactivity.
Source: Alzheimer's Foundation, Dementia Center
