Many people who struggle with sleep are worried by reports from small studies and popular science books about how sleep affects us, says the Norwegian brain researcher Anders Fjell.
Many people who struggle with sleep are worried by reports from small studies and popular science books about how sleep affects us, says the Norwegian brain researcher Anders Fjell.

Norwegian brain researcher:
You don’t need to worry about getting Alzheimer's if you’re a little short on sleep

Sleep researchers regularly warn that poor or too little sleep can lead to Alzheimer's disease. But a group of Norwegian brain researchers who are behind a large research project haven’t found this connection.

Published

As recently as last week, a new scientific article was published on the connection between Alzheimer's and sleep.

American researchers studied 32 elderly people and found a correlation between poor sleep quality and the accumulation of plaque in the brain, called beta-amyloid. Researchers know this is a key player in the development of Alzheimer's disease.

One of the researchers behind the study is Matthew Walker, a researcher at the University of California. He has written the international bestseller "Why we sleep", a book about the importance of sleep for our health.

Need to know more

Anders Fjell is a Norwegian brain researcher at the University of Oslo (UiO) who studies the brain from a life course perspective. He believes we need much more scientific support to accurately describe what sleep means to the brain.

Fjell believes that small experimental studies and popular science books, such as the one Walker has written, have unnecessarily worried many people who struggle with sleep.

His research group is running a large project called Lifebrain, in which one of the topics is brain health and sleep.

“Our research suggests most people don’t have any reason to worry,” he says.

Anders Fjell and his colleagues at the University of Oslo are working with data from thousands of participants. These large studies show that there are very modest associations between quality of sleep and brain health.
Anders Fjell and his colleagues at the University of Oslo are working with data from thousands of participants. These large studies show that there are very modest associations between quality of sleep and brain health.

Chicken or egg?

Researchers know that diseases that affect the brain, such as Alzheimer's and Parkinson's, are associated with poorer sleep quality. In several experiments where researchers have restricted the amount of sleep in a group of people or animals over a long period, they have found more of certain proteins in the brain that are known to be important in Alzheimer's disease.

But they know nothing about the causal relationship. There is still a lot of discussion in the professional community about this, says Fjell.

“Is it the sleep problems themselves that cause the disease, or is it the opposite? Is it possible that people whose brain health isn’t optimal are also the people who have problems sleeping?” asks Fjell.

Have studied many thousands

In a study published six years ago, researchers at UiO followed roughly 150 people over time.

The participants filled out a questionnaire about their sleep habits, where they were asked, among other things, how long they slept, how long it took them to fall asleep at night and whether they used sleeping pills. All participants had brain scans twice with an MRI, three-and-a-half-years apart.

The researchers found that the brain volume in participants with sleep problems was reduced faster during the course of the study than those without sleep problems. The reduction in brain volume was more pronounced in people over 60.

“When we studied this again in a sample of more than 20,000 people, we also found these effects. But they are very modest. This means that the effects have almost no significance for the brain health of any one individual,” Fjell said.

Smaller hippocampus

The Lifebrain researchers have been particularly interested in the brain structure called the hippocampus. This structure is absolutely critical for memory. If your hippocampus doesn’t work, your memory will be almost non-existent. The hippocampus is also the part of the brain that is most altered by Alzheimer's.

The researchers divided more than 20,000 study participants into two groups, one group that sleeps well and one that doesn’t sleep so well. They then found something interesting.

People who slept very little, meaning less than five hours every night, and those who slept more than ten hours a night had a smaller hippocampus than others.

This connection remains stable throughout life. The relationship between sleep and hippocampus loss is the same for 20-year-olds and 80-year-olds.

Is there an underlying disease?

Fjell thinks it’s interesting that they only saw an effect at the extremes, meaning it was only in people who got a lot or very little sleep where they saw a connection to the size of the hippocampus.

“These data show us that for the vast majority of us, whose sleep amounts are somewhere in between, there is no connection between how long we sleep and the size of the hippocampus,” he said.

“It is also interesting that sleeping a lot was at least as strongly related to having a small hippocampus as sleeping a little,” Fjell said.

He and his colleagues wonder if people who sleep much more or less than normal have some kind of underlying disease. If that’s true, it would explain why they have small hippocampal volumes — and why they sleep poorly.

Will create guidelines

The research group at the University of Oslo is now well underway with a large study where they are looking at whether there is a connection between sleep duration and changes in the brain throughout life.

“The goal is to find out how much we have to sleep to prevent negative effects on the brain,” Fjell said.

In 2015, the National Sleep Foundation in the United States published guidelines for how much you should sleep from the time you are a baby until you are old to maintain a healthy body. These guidelines were formulated by sleep experts who agreed on what should be recommended.

“We want to do the same for brain health, but more directly based on empirical data,” Fjell said.

The results of this study are not yet ready.

Most people get enough sleep

Nevertheless, sleep does matter, Fjell said. But that doesn’t mean that we should all struggle to sleep eight hours every night.

“The most important thing is to get enough sleep so that you feel rested and that your daily life is going well. If you sleep five hours and feel good, there’s probably no need to worry. I think it's the extremes, on both ends, that are associated with poorer brain health,” he said.

Translated by: Nancy Bazilchuk

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Read the Norwegian version of this article on forskning.no