Experts say sleeping too much can affect cognitive function

Health experts have long stressed the positive impact of quality sleep on cognitive abilities, but too much of a good thing can also be bad.

Cognitive skills are essential because they help with memory, thinking, attention, learning and other crucial brain functions.

While many experts recommend that the average adult sleep between seven and nine hours daily, a new study has found that "sleeping nine hours or more per night is associated with worse cognitive performance".

The effects were worse for people battling depression.

Researchers from the University of Texas Health Science Centre conducted the study. A total of 1,853 dementia and stroke-free people, aged 27 to 85, participated in the research.

“Long but not short sleep duration was associated with poorer global cognition and specific cognitive abilities like memory, visuospatial skills and executive functions," behavioural neurologist Sudha Seshadri said, per the university's website.

"These associations were stronger in people with depressive symptoms, regardless of antidepressant usage."

The study also found that people who sleep for more extended periods "are more likely to report symptoms of depression".

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Sleeping too much could also increase the risk of dementia.

"The cognitive effects of depression appear to persist even after remission of depressive symptoms, contributing to a heightened vulnerability to dementia later in life.

"This complex relationship suggests that depression may modify the relationship between sleep and cognition, potentially amplifying the cognitive impact of inadequate sleep duration," the study said.

According to the Alzheimer's Association, "dementia is a general term for loss of memory, language, problem-solving and other thinking abilities that are severe enough to interfere with daily life. Alzheimer's is the most common cause of dementia."

Several studies have shown that cases of dementia are on the rise globally.

Well-known dementia sufferers include Bruce Willis and Wendy Williams.

Former Bafana Bafana coach Clive Barker died in 2023 after battling Lewy Body Dementia (LBD). He was 78.

The University of Texas Health Science Centre study's findings "suggest that sleeping ≥ 9 hours per night is associated with cognitive differences equivalent to 6.5 years of brain ageing."

Disclaimer: Health-related information provided in this article is not a substitute for medical advice and should not be used to diagnose or treat health problems. It is always advisable to consult with your doctor on any health-related issues.