The Relationship between Sleep and Alzheimer's Disease

Alzheimer's disease is a neurological disease that affects daily life and cognitive activities and progresses with behavioral changes. Age is one of the most important factors in the development of Alzheimer's disease, which occurs as healthy brain cells die. Today, advances in medicine are extending human life expectancy, and the population's average age is increasing. As a result, Alzheimer's disease is becoming more common worldwide. Despite all this, the disease, about which we know very little, continues to stimulate scientific curiosity.

The Study on Alzheimer's Disease and Sleep

On 11 February 2021, a study by Dr Rebecca S. Robbins of Boston's Brigham and Women's Hospital investigating sleep disorders and their relationship with Alzheimer's disease appeared in the Journal of Aging. This study claimed that the onset and development of Alzheimer's disease were linked to sleep disorders.

Journal of Aging published the study, which selected 2,812 people aged 65 and older from the National Health and Aging Trends Study (NHATS) in the United States. Their average age was 76.9, and 60% were women. These people completed a questionnaire in 2013 and 2014 assessing sleep disorders and sleep duration. Using these data, researchers closely examined the relationship between dementia and other causes of death and sleep timing and sleep disorders over 5 years.

Results

According to the questionnaire results, 60% of participants said they generally did not feel sleepy during the day. Approximately half of the group reported rarely taking short naps or never doing so. Regarding time to fall asleep, more than half said they fell asleep in 15 minutes or less. Nearly 70% described their sleep quality as very good or good, and finally, more than 90% said they rarely or never snored.

Based on their analysis of the questionnaires, the researchers reported a 2 times greater risk of dementia in people who slept 5 hours or less a night. They added that those who took 30 minutes or longer to fall asleep also had an increased risk of dementia.

In addition to these results, problems that could lead to death were observed more often in people who had difficulty staying awake during the day, napped during the day, and had poor sleep quality.

The researchers also noted that these findings came from a small community and that some factors were limited.

Long Sleep, Like Short Sleep, May Indicate Poor Health

Dr Rebecca's data are very new. We undoubtedly need time to be certain of their accuracy. However, it is useful to acknowledge that sleeping less than 5 hours may adversely affect our health. So how does sleeping too much affect health?

In a study also conducted at Boston's Brigham and Women's Hospital, Dr Lei Gao states that people with sleep apnea (temporary pauses in breathing during sleep) or those who sleep more than 9 hours a night may have up to a 2 times greater risk of developing Alzheimer's disease.

A UK Biobank study investigating the relationship between sleep disorders and brain health selected more than 500,000 people without Alzheimer's disease whose average age was 57. They were followed for approximately 12 years.

Participants were asked to report variables individually, including their sleep patterns, frequency of daytime napping, presence of sleep apnea, and snoring.

Follow-up showed that people who slept more than 9 hours a night had a higher risk of Alzheimer's disease than those who slept 6-9 hours.

Dr Gao emphasized that this increase was related to age and stated that they had found no evidence that daytime napping increased Alzheimer's risk at younger ages.

Commentary

As the two studies above show, sleep is more important in our lives than we might think. However, the studies also had various limitations, and more research is therefore needed. During particular periods, people may temporarily have short or irregular sleep. Alongside exercise and nutrition, adequate, good-quality sleep clearly plays an important role in completing healthy lifestyle habits. These studies are therefore important for demonstrating sleep's contribution in relation to Alzheimer's disease, in addition to the many benefits of adequate, regular sleep.