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Depression and risk of dementia in older adults


HQ Team

October 25, 2022: Dementia is the seventh leading cause of death and affects around 55 million people worldwide, with nearly 10 million new cases added every year, according to the World Health Organization. Several studies have shown that depression raises the risk of dementia. Currently, there is no available treatment to cure dementia.

Researchers at Fudan University in Shanghai, China, have published a study in Biological Psychiatry that explores associations between different depression trajectories, depression treatments, and the likelihood of developing dementia.

“This is very interesting. As we have said before (all laid out in the 2020 Lancet Commission on dementia), few previous studies have distinguished between treated and untreated depression. […],” said Dr. Gill Livingstone, professor of psychiatry of older people at University College London and leader of the Lancet Commission on dementia.

The study observed people with depression aged over 50 for 10 to 14 years and found a nearly identical increased risk of dementia (51%). among those who had depressive symptoms or got worse over time, [while] those who were treated and were not highly depressed had a reduction i[n] risk.

“This is an important finding and suggests people in mid to late life with depression should be treated energetically to improve symptom[s], helping their quality of life and decreasing their likelihood of developing dementia.”
— Dr. Gill Livingstone

The study participants, 354,313 individuals, were picked from the UK Biobank (period 2006-2010) aged between 50 and 70. 189,440 participants (53.5%) were women.

A total of 46,280 participants were diagnosed with late-life depression at baseline, of whom 725 developed dementia during the follow-up period. The researchers followed up with the participants until 2020.

To study the effect of different depression trajectories on the rate of dementia, the researchers identified 4 subgroups.

Depression and dementia risk

The researchers found that study participants with depression had a 51% higher risk of dementia than those without depression.

In the participants with depression, the risk of developing dementia differed depending on their depression trajectory. Individuals with ‘increasing’, ‘chronically high’ and ‘chronically low’ depression symptoms had a higher risk of developing dementia, whereas individuals with ‘decreasing’ levels of depression had the same dementia risk as individuals without depression.

The researchers found that depression treatments are associated with a lower incidence of dementia, with an approximately 26% lower risk of dementia among patients who received treatment.

Moreover, the researchers found that an ‘increasing’ depression trajectory raises the risk of dementia , taking depression therapies helps in stemming this risk. People with chronically high level of depression received no benefit from depression treatments on the risk of dementia.

Dr. Wei Cheng, study co-leader and a young principal investigator at the Institute of Science and Technology for Brain-Inspired Intelligence (ISTBI) at Fudan University, says the findings from this study “shed some light on previous work as well. The differences of effectiveness across depression courses might explain the discrepancy between previous studies.”

The researchers note that studies so far have “proved inconclusive that whether depression is a prodromal phase (symptom) or an independent risk factor for dementia..” Thus, they say the link between depression and dementia “should still be interpreted with caution.”

Dr. Livingstone reiterated this in her comments to MNT: “Depression might be a risk for dementia, but, in later life, dementia might cause depression.”

Other studies

Depression can be treated using psychotherapy and pharmacotherapy. There are some studies that have shown medicines and therapy can lower the risk of later-life dementia, sometimes.

2017 study by found that long-term selective serotonin reuptake inhibitors or SSRI treatment may delay the progression from mild cognitive impairment to Alzheimer’s dementia.

Another 2017 study found that the use of antidepressants did not make a difference in the risk of dementia, while a 2016 study concluded that the use of antidepressants in the elderly was associated with an increased risk of dementia.

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