Six to 8 hours of good quality sleep delays cognitive decline, suggests a new study published in the journal Brain.¹

Researchers monitored sleep-wake activity of 100 older adults over 4–6 nights. They were also examined for cognitive decline and Alzheimers disease by way of APOE genotyping, measurement of total tau and amyloid-β42 in the CSF and different types of neuropsychological tests (Free and Cued Selective Reminding test, the Logical Memory Delayed Recall assessment, the Digit Symbol Substitution test and the Mini-Mental State Examination).

Results showed that only those individuals who slept 6 to 8 hours had good cognitive function, while cognitive decline was observed in those at either ends of the spectrum i.e., those who slept for ≤5.5 hours and those who slept for ≥7.5 hours.

This study recommends that it’s the quality of sleep, and not the hours of sleep, that may have a role in cognition. It further submits that neither too little nor too much sleep is beneficial. There is an optimum amount of sleep, or what has been called by the authors as the “sweet spot for total sleep time”, which helps to maintain cognitive function.

“The "sweet spot" for sleep is when you can sleep continuously through the four stages of sleep four to six times each night. Since each cycle is roughly 90 minutes long, most people need seven to eight hours of relatively uninterrupted sleep to achieve this goal.”²

Treatment of sleep disturbances may have a beneficial effect on cognition in individuals with early Alzheimer’s disease suggesting sleep quality as a modifiable risk factor for cognitive decline.

Here are few tips for good sleep hygiene.

• Wake up and go to sleep at the same time each day.
• Keep the lights dim.
• Remove all electronic devices.
• Avoid eating a heavy meal or doing any vigorous physical activity before sleeping.
• Limit intake of caffeinated beverages within 6 hours of bedtime.
• Getting regular aerobic exercise such as walking, jogging, or swimming can help you fall asleep faster, get more deep sleep, and awaken less often during the night.
• Track your sleep patterns for a week or two and keep a record. If you find that you’re spending less than 80% of your time in bed asleep, you may be spending too much time in bed. Try going to bed later, and don’t nap during the day. If you find yourself falling asleep too early in the evening, keep the lights bright.
• Avoid looking at the clock or turn the clock face where you cannot see it.
• Try meditation, deep breathing, or progressive muscle relaxation to calm your mind and relax the muscles.

Reference

1. Lucey BP, et al. Sleep and longitudinal cognitive performance in preclinical and early symptomatic Alzheimer’s disease. Brain. October 20, 2021; awab272, https://doi.org/10.1093/brain/awab272.
2. Stages of Sleep | Michigan Medicine. https://www.uofmhealth.org/health-library/hw48331