Depression has long been linked to an increased risk of dementia, and now a new study shows that prompt treatment of depression may reduce dementia risk in some patient populations.
The study’s findings were published in the journal Biological Psychiatry. Dementia, a disabling neurocognitive condition that primarily affects older adults, affects over 55 million people worldwide. There is no effective treatment for dementia, but identifying ways to help minimise or prevent dementia would help to reduce the disease’s burden.
The study was led by Jin-Tai Yu, MD, PhD, of Huashan Hospital, Shanghai Medical College, Fudan University, and Wei Cheng, PhD, of Fudan University’s Institute of Science and Technology for Brain-Inspired Intelligence. It was published in the journal Biological Psychiatry by Elsevier.
Professor Yu and Professor Cheng analysed data from the UK Biobank, a population-based cohort of over 500,000 people. The current study included over 350,000 people, including 46,280 people who were depressed. 725 of the depressed patients developed dementia during the course of the study.
Previous research into whether depression treatments such as pharmacotherapy and psychotherapy could reduce the risk of dementia yielded conflicting results, leaving the question unanswered. “Older people appear to experience different depression patterns over time,” Professor Yu explained.
“As a result, intra-individual variability in symptoms may confer a different risk of dementia as well as heterogeneity in depression treatment effectiveness in relation to dementia prevention.”
To address this heterogeneity, the researchers classified participants into one of four depression courses: increasing course, in which mild initial symptoms steadily increase; decreasing course, in which moderate- or high-severity symptoms begin but then decrease; chronically high course, in which severe depressive symptoms persist; and chronically low course, in which mild or moderate depressive symptoms persist.
Depression, as expected, increased the risk of dementia by 51% when compared to non-depressed participants, according to the study.
The degree of risk, however, was determined by the course of depression; those with increasing, chronically high, or chronically low course depression were more vulnerable to dementia, whereas those with decreasing course faced no greater risk than those without depression.
The researchers were most interested in learning whether receiving depression treatment could reduce the increased risk of dementia. Overall, depressed participants who received treatment had a 30% lower risk of dementia than untreated participants. When the researchers separated the participants based on depression course, they discovered that those with increasing and chronically low courses of depression had a lower risk of dementia with treatment, whereas those with a chronically high course had no benefit in terms of dementia risk.
“Once again, the course of ineffectively treated depression carries significant medical risk,” said John Krystal, MD, editor of Biological Psychiatry, noting that “in this case, symptomatic depression increases dementia risk by 51%, whereas treatment was associated with a significant reduction in this risk.”
“This suggests that timely depression treatment is required among those with late-life depression,” Professor Cheng added. “Providing depression treatment to those suffering from late-life depression may not only alleviate affective symptoms but also delay the onset of dementia.”
“The new findings shed some light on previous work,” Professor Cheng said. “The disparity between previous studies may be explained by differences in effectiveness across depression courses.”