BrainSleep: Does sleep duration affect sleep?

Rationale

There is a worry in society that too little sleep is a pervasive negative factor for somatic, mental and cognitive health, with suggestions that we are suffering an ‘epidemic of sleeplessness'. Reviewing the research on the relationship between sleep duration and the brain, we came to the conclusion that there is as of yet no conclusive evidence showing that short sleep causes poorer brain health.

Objective and methods

The ambitious objective of BrainSleep is directly to test the relationship between sleep duration and brain health and to decide to what degree such a relationship may be causal. We will create a database of > 70.000 structural and functional MRIs of the brain from > 60.000 participants, including 5000 longitudinal examinations covering intervals up more than a decade.

BrainSleep will use novel approaches to MRI analyses, integrating multiple structural, microstructural and functional measures in the same analyses, yielding biologically more meaningful variables and higher sensitivity. Sleep will be measured in a natural setting, combining standardized self-report measures with objective sleep registrations. To address the problem of causality, we will assess genetic pleiotropy between sleep duration and brain measures and run Mendelian randomization analyses where genetic variation is used as a natural experiment to investigate the causal relations. This will be combined with causal inference methods applied to longitudinal data, where we will test whether changes in sleep duration over time precede or follow changes in brain features, and by scrutinizing effects of a range of somatic and mental health variables which may cause spurious relationships between sleep duration and brain health. The analyses will be enriched by a sample of 200 participants who in addition to structural and functional MRI will undergo repeated polysomnography, allowing us directly to study sleep architecture underlying macro-measures of sleep in the large-scale analyses.

Publications

Individual sleep need is flexible and dynamically related to cognitive function. Nature Human Behaviour 2024

Anders M. Fjell et.al: No phenotypic or genotypic evidence for a link between sleep duration and brain atrophy. Nature Human Behaviour 2023.

The status of the project

We are currently in the process of recruiting for this ongoing project.

Funding

The project has received funding from the Norwegian Research Council under grant nr. 325878 "Does sleep duration affect the brain?".