Why white matter matters in insomnia
Changes in white matter could hold the key to understanding insomnia.
Insomnia is characterized by a difficulty in falling asleep, staying asleep or both.
The resultant lack of sleep causes deficits that leach into every facet of an insomniac’s life.
Energy levels, mood, health, relationships and performance at work can all take a substantial kick.
According to the American Sleep Association, 1 in 3 adults will experience insomnia at some point in their life, and 1 in 10 will face chronic insomnia.
Women tend to suffer from insomnia slightly more often than men, and it becomes more common as we age.
Surface causes of chronic sleeplessness include stress, caffeine intake or medical conditions, such as stroke or an overactive thyroid. Other factors can include pain, anxiety and depression, but the underlying neuroscience of insomnia has proven difficult to pin down.
The origins of insomnia in the brain
Modern imaging techniques, such as MRI (magnetic resonance imaging), provide an extra dimension to insomnia studies. They have allowed investigators to visualize insomnia-related metabolic changes in certain areas of the brain, such as the amygdala and thalamus. To date, however, results have been contradictory.
A team of researchers, led by Dr. Guihua Jiang from Guangdong No. 2 Provincial People’s Hospital in Guangzhou, China, decided to focus their investigation into insomnia on the white matter of the brain – the pathways that send messages between brain regions.
The team hoped to match abnormalities in white matter to features of insomnia; Shumei Li, part of the research team, explains the role of white matter in brief:
“White matter tracts are bundles of axons – or long fibers of nerve cells – that connect one part of the brain to another. If white matter tracts are impaired, communication between brain regions is disrupted.”
White matter makes up the bulk of deep brain tissue and is so-called as a result of its white coloration in comparison to the adjoining gray matter. This whiteness is caused by a fatty outer coating called the myelin sheath, which protects the nerves and allows them to conduct signals more quickly and efficiently.
Initially, white matter was considered to be little more than a passive message carrier. However, it is now known to be involved in learning and information processing.
Investigating white matter
For the study, 23 individuals with insomnia were scanned and compared with 30 healthy controls. Before entering the MRI scanner, each completed a barrage of questionnaires, including the Insomnia Severity Index, the Pittsburgh Sleep Quality Index, the Self-Rating Anxiety Scale and the Self-Rating Depression Scale.
The participants received a specific type of MRI scan, referred to as diffusion tensor imaging (DTI). DTI charts the movement of water along white matter tracts and allows researchers to pinpoint any weak spots.
The data, manipulated using an advanced analysis technique called Tract-Based Spatial Statistics, yielded fascinating results. The brains of participants with insomnia showed a significant reduction in white matter integrity in sections of the right brain and the thalamus. In regard to the specific regions, Li says:
“These impaired white matter tracts are mainly involved in the regulation of sleep and wakefulness, cognitive function and sensorimotor function.”
The deficits measured in the thalamus correlated with the duration of insomnia; the changes in the corpus callosum (the largest portion of white matter in the brain) correlated with self-rated depression scores.
Interestingly, the types of abnormalities that the team found appeared to be related to their myelin coating.
This discovery of abnormalities in the thalamus seems particularly pertinent; sitting deep in the center of the brain, the thalamus houses the body’s biological clock and is known to play a significant role in sleep, alertness and consciousness.
The authors note that the study was small and more work needs to be done, but the results are intriguing and could spawn a fresh way to approach insomnia and its treatment.
Medical News Today recently covered research shedding new light on urban sleep disorders.