A study published in the June 12, 2024, online issue of Neurology®, the medical journal of the American Academy of Neurology, reveals that individuals experiencing prolonged depressive symptoms from young adulthood may face impaired thinking and memory skills by middle age. The research also indicates that depressive symptoms are more frequently reported by Black adults compared to white adults (1^✔ ✔Trusted Source
Long-term depressive symptoms and midlife brain age

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“The mechanisms that lead to dementia begin well before the disease’s symptoms manifest, and previous studies have demonstrated that Black adults are at a higher risk of developing dementia than white adults,” explained study author Leslie Grasset, PhD, from the University of Bordeaux in France. “Our study shows that extended exposure to high levels of depressive symptoms in young adulthood negatively impacts cognitive functions in middle age, particularly among Black adults.”

Extended depression and decreased in cognitive function

The study involved 3,117 people with an average age of 30 at the start of the study of participants, 47% were Black and 53% were white.

Participants were evaluated for depressive symptoms every five years for 20 years. At each visit, they completed a questionnaire asking if they experienced changes in appetite or sleep, had problems with concentration, or experienced feelings of worthlessness, sadness, or loneliness. Higher scores represented more symptoms.

Researchers divided participants into four groups based on the progression of their symptoms over time: persistently low symptoms, medium decreasing, persistently medium or high increasing symptoms. There was a higher proportion of Black participants, 52%, in the persistently medium group, as well as the high increasing depressive symptoms group with 70%.

Five years later, when participants had an average age of 55, they were given three tests to examine thinking and memory skills.

For example, on a test that measures processing speed and memory, participants were given a key showing numbers and corresponding symbols. They then had to draw those symbols on a separate list of random numbers as quickly as possible. The score range was zero to 133 with lower scores representing worse cognition. Those in the low symptom group had an average score of 73, in the medium decreasing group, an average score of 71, persistently medium, a score of 66 and high increasing, an average score of 57.

After adjusting for factors such as age, physical activity, and total cholesterol, among Black participants, those in the high-symptom group had an average score that was 0.64 standard deviations below the average score for the low symptom group. Among white participants, those in the high-symptom group had an average score of 0.40 standard deviations below the average score for the low symptom group.

Researchers created a standardized score for each of the three cognitive tests. After adjusting for factors such as education, blood pressure, and total cholesterol, researchers found among Black participants, those in the three groups with high and medium symptoms had worse verbal memory, processing speed, and executive function scores when compared to those in the low group.

Researchers found among white participants, those in the high symptom group had worse verbal memory and processing speed scores when compared to those in the low symptom group.

“Our results suggest that Black adults are not only more likely to experience worse depressive symptoms trajectories, but these symptoms may lead to worse repercussions on thinking and memory as early as middle age,” said Grasset. “This may help explain some of the disparities in dementia risk at older age.”

Grasset said, “Having more depressive symptoms may be due to inequalities in socioeconomic resources such as housing and income, as well as access to health care and treatment. Racial inequalities should be accounted for when designing interventions to reduce a person’s risk of dementia.”

A limitation of the study was that symptoms were self-reported and no clinical diagnosis of depression was available. It is possible that some participants may not have accurately reported their symptoms.

Reference:

1. Long-term depressive symptoms and midlife brain age – (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10115134/)

Source-Medindia