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Sleep quality linked to cognitive decline

Studies reveal the benefits of a good night’s sleep at all stages of life.

  • Health
  • Read Time: 5 mins

People who face disrupted sleep in their 30s and 40s are more than twice as likely as others to experience cognitive decline in later life, according to researchers.

A long-term study begun in the early 2000s used wrist-worn activity monitors to track the quality of sleep experienced by hundreds of people aged around 40. On average, they were found to sleep about six hours a night.

In 2015 and 2016, researchers tested 526 of the participants from the earlier study, and found that those who experienced more sleep fragmentation, or spent a greater share of their sleeping hours moving, were more likely to receive poor scores on standard cognitive tests more than a decade later.

The research, published in the medical journal Neurology, found that people who slept less or who had higher sleep fragmentation were significantly more likely to be male, to be Black, to have a higher body mass index (BMI), and to have a history of depression or hypertension.

Study author Dr Yue Leng, an associate professor of psychiatry at the University of California, San Francisco, said, “Given that signs of Alzheimer’s disease start to accumulate in the brain several decades before symptoms begin, understanding the connection between sleep and cognition earlier in life is critical for understanding the role of sleep problems as a risk factor for the disease.”

Health benefits

Experts, including those at the Centers for Disease Control and Prevention (CDC), say we should get between seven and 10 hours of sleep a night, with adults needing less than children and teenagers.

However, a YouGov survey showed that 32% Australians do not get sufficient shut-eye.

Disrupted sleep is associated with a higher risk of conditions including diabetes, stroke, cardiovascular disease, and dementia.

“More research is needed to assess the link between sleep disturbances and cognition at different stages of life and to identify if critical life periods exist when sleep is more strongly associated with cognition,” Dr Leng said.

“Future studies could open up new opportunities for the prevention of Alzheimer’s disease later in life.”

Dementia risks

Sleep is not just important in younger adulthood.

Researchers in Europe recently examined data from almost 8,000 participants in a different study and found that consistently sleeping six hours or less at age 50, 60, and 70 was associated with a 30% increase in dementia risk compared to a normal sleep duration of seven hours.

The average age of dementia diagnosis was 77.

The good news is that whatever your age, more sleep may help ward-off dementia.

According to the Harvard Health Blog, strategies for a good night’s sleep include:

  • Get up at the same time every day, including weekends. This helps set your body’s natural clock (circadian rhythm) and prevents oversleeping on one day affecting your ability to sleep the next. 

  • Go to bed when you feel sleepy, not just feel it’s time to go to bed. 

  • If your brain is busy thinking, writing down your concerns each evening may help calm you down. 

  • Put away mobile phones, tablet computers, and other electronics two hours before bedtime. 

  • Only use your bed for sleeping and sex. 

Further reading: CNN, Harvard Health Blog  

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