Lifebrain Newsletter January 2021
 

Do you need to be worried about your brain health if you sleep too little?

There is a worry in society that too little sleep has strong negative effects on physical, mental and cognitive health. Some have even suggested that we are suffering an ‘epidemic of sleeplessness” in modern societies. Lack of sleep is also a concern for brain health, and we know that old people with sleep problems have a higher risk of developing Alzheimer’s Disease and other dementias.

Poor sleep quality is related to modest loss of brain volume in all age groups

So how much should you sleep in order to take care of your brain? This and related questions have been studied by the researchers in the Lifebrain consortium, taking advantage of magnetic resonance images (MRI) of the brains of thousands of participants across the adult lifespan. This information was coupled to questionnaires about sleep habits. 

The results showed that poor sleep was related to more loss of brain volume over time. Participants with sleep problems, like nocturnal awakenings or trouble falling asleep at night, and who rated their sleep quality as low and were tired during the day, showed slightly more loss of brain volume than participants without these problems. Mostly, the relationships did not vary with age, so that the relationship between poor sleep and brain change was similar for people in their 20ties and 70ties. However, there were some exceptions. Sleep problems were only related to thinning of the cerebral cortex in participants above 60 years of age.

Sleeping too much or too little might negatively impact brain health

So how much sleep is enough to take care of your brain? We did not find convincing evidence that how much people report to sleep is related to how their brain ages. Studies of mortality tend to show that very short and very long sleep duration is associated with death and poor somatic health. We did not see such a pattern for the brain in our study. This could be due to very few people sleeping for very short or very long hours in our study. However, when we investigated only those who reported to sleep less than 5 hours every night or more than 10 hours, we found that they had smaller volumes of hippocampus, a brain structure critical for learning and memory. Thus, although how much sleep people got in general was not related to their brain aging, we cannot exclude the possibility that sleeping very little or very much is related to poorer brain health.

Limitation of sleep studies: the chicken or the egg?

Two important aspects need to be taken into account. First, the relationships we found were not very strong. Thus, although poor sleep generally was related to more brain changes, the effects were modest. Some people with poor sleep show little brain aging compared to others, whereas some with good sleep showed more.

Second, we do not know whether poor sleep causes more brain ageing, or whether poor sleep is merely a reflection of something that goes on in the brain, without having any direct effect by itself. Experiments with sleep deprivation both in animals and humans support both these possibilities: poor sleep may have negative effects on the brain, but poor brain health is also likely to affect sleep.
Experimental studies and large-scale genetic investigations can contribute to clarify the causal effect when it comes to sleep and brain health.

References

Anders M Fjell, Øystein Sørensen, Inge K Amlien, David Bartrés-Faz et al.: Poor Self-Reported Sleep is Related to Regional Cortical Thinning in Aging but not Memory Decline-Results From the Lifebrain Consortium. Cerebral Cortex, 2020 Nov 25. 

Anders M Fjell, Øystein Sørensen, Inge K Amlien, David Bartrés-Faz et al.: Self-reported sleep relates to hippocampal atrophy across the adult lifespan: results from the Lifebrain consortium. Sleep. Volume 43, Issue 5, May 2020

Source of newsletter

This newsletter was edited by Anders M. Fjell, Professor of Cognitive Psychology, Center for Lifespan Changes in Brain and Cognition, Department of Psychology, University of Oslo.

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