Chronic insomniacs losing out on sleep may also be missing brain matter.
For the first time, brain imaging has linked chronic insomnia to lower gray matter density in areas that regulate the brain's ability to make decisions and to rest. The research could lead to new treatment plans for people who struggle with sleeplessness.
"The findings predict that chronic insomnia sufferers may have compromised capacities to evaluate the affective value of stimuli," says Ellemarijie Altena, lead author of the study from the Netherlands Institute for Neuroscience.
"This could have consequences for other cognitive processes, notably decision-making."
The study, published in Biological Psychiatry, compared the white and grey matter volumes of 24 older, chronic insomnia patients to 13 normal sleepers, and controlled for physical and psychiatric disorders that could also alter brain densities.
Severe insomniacs exhibited the most extensive density loss, regardless of how long they had suffered from the disorder.
Cause and effect
However, the researchers are not yet able to pin down whether sleeplessness precedes grey matter loss or the other way around.
"We can't say what comes first: the lower grey matter density or the insomnia, but (the data) suggests that a low orbitofrontal gray matter density may be a risk factor to develop insomnia," says Altena, now a research associate at the Cambridge University Department of Clinical Neurosciences. "We only investigated older people, so follow-up studies at different ages could hopefully in the future determine what comes first."
Sleep researchers have long recognised that insomnia disrupts brain functioning and behaviour, but this study begins to answer why that malfunctioning happens - and how to more effectively treat it.
"This article is fitting with a growing literature (showing that) bad sleep is bad for the brain at a neurological level, not just the psychiatric level as a nuisance," says Dr Ronald Kramer, a neurologist and director of the Sleep Disorders Center at the Colorado Neurology Institute.
By drawing attention to the neurological damage that sleep disorders can inflict, both Kramer and Altena hope this study and similar research will lead to more accurate and diverse treatment options for chronic insomnia.
"This is the start of perhaps moving insomnia to a more medically based paradigm, which is when you have a problem, we get a test, we get a specific diagnosis and a treatment plan," says Kramer.