Middle- to old-age depression likely tied to dementia

The study, led by Japan's National Institutes for Quantum Science and Technology, or QST, is expected to lead to early detection and treatments based on objective diagnoses of dementia, because the cognitive functions of participating patients were normal at the time of analysis.

The QST in 2020 developed a method to create high-definition images of tau protein in brains by using positron emission tomography.

The research team examined 52 patients diagnosed at age 40 or more with mood disorders, such as depression and bipolar disorder, and 47 healthy individuals of the same age group to check the presence and distribution of brain lesions caused by tau protein accumulation.

Lesions were found in 50 pct of the patients and 14.9 pct of the healthy individuals.

In patients with symptoms such as delusions and hallucinations, amounts of tau protein accumulation were larger in specific regions, such as the striatum and the frontal lobe.

The team also analyzed the results of 208 autopsies of brains donated after death.

Brain lesions caused by tau protein accumulation were seen in 57.1 pct of the 21 cases who developed mood disorders aged 40 or older.

Some of them later developed dementia, and it took an average of seven years from the diagnosis of mood disorder until the onset of dementia symptoms.