Scientists Discover Alzheimer’s Clues in Brain Decades before Symptoms Emerge

A study, published in The Lancet Healthy Longevity, based on data from the Finnish population reveals that indicators of Alzheimer’s disease can be present in the brain as early as middle age. In the years ahead, detecting Alzheimer’s-related biomarkers through blood samples could enable earlier diagnosis and make it possible to direct preventive interventions to those most likely to benefit, while symptoms are still minimal.

With an aging population, Alzheimer’s and other forms of dementia are increasingly widespread. However, the biological changes that drive these conditions often start long before any noticeable cognitive decline, including memory loss, begins to appear.

Researchers at the University of Turku in Finland discovered that some individuals in middle age already show elevated levels of blood biomarkers linked to Alzheimer’s disease, with concentrations tending to rise as people get older.

One notable observation was that individuals whose parents—especially mothers—had high biomarker levels were more likely to exhibit elevated levels themselves in midlife. The study also revealed a possible connection between kidney disease and increased biomarker concentrations during middle age.

While the APOE ε4 gene is known to raise the risk of Alzheimer’s, its association with higher blood-based biomarker levels was only seen in older adults, not yet in those who are middle-aged.

Recently, it has become possible to identify biomarkers associated with Alzheimer’s disease through a blood sample. In the future, this offers a cost-effective method for identifying those at greatest risk of developing Alzheimer’s disease and prioritizing them for preventive treatments.

“In clinical practice, detecting beta-amyloid pathology associated with Alzheimer’s disease currently requires imaging studies or cerebrospinal fluid sampling. However, recently developed ultrasensitive measurement technologies now allow the detection of Alzheimer’s disease-related brain biomarkers from blood samples,” says Suvi Rovio, Senior Researcher at the Research Centre of Applied and Preventive Cardiovascular Medicine at the University of Turku, who led the study.

It is not yet possible to definitively diagnose Alzheimer’s disease with a blood sample, as the method is still limited by the lack of well-known reference values. Additionally, it remains unclear which confounding factors influence biomarker concentrations in blood related to Alzheimer’s disease. Therefore, the interpretations of the biomarkers obtained from blood sample could lead to misdiagnosis.

“In order to reliably use blood-based biomarkers for Alzheimer’s disease diagnosis in the future, more research is needed across different population and age groups to standardize reference values,” highlights Rovio.

In the study, biomarkers associated with Alzheimer’s disease were measured from blood samples of middle-aged participants (aged 41–56) and their parents (aged 59–90), with a total sample size of 2,051 individuals.

“Until now, brain biomarkers associated with Alzheimer’s disease have mainly been studied in older individuals. Our study provides new insights into biomarker levels and associated factors starting from middle age,” says Marja Heiskanen, Senior Researcher at the Research Centre of Applied and Preventive Cardiovascular Medicine at the University of Turku.

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