Summary: Researchers have identified five different subtypes of the sleep disorder insomnia, including difficulty falling asleep and early morning awakening. The study reports insomnia subtypes may be identified by examining personality traits of sufferers.
Researchers at the Netherlands Institute for Neuroscience revealed that there are five types of insomnia. This finding was published on Monday January 7 by The Lancet Psychiatry. A commentary in the journal stated that the finding could be a new page in the history of insomnia, promoting discoveries on mechanisms and interventions.
Insomnia is a major problem
One out of ten people suffer from chronic insomnia: it’s the second-most prevalent and burdensome mental disorder. Findings on underlying brain mechanisms have been inconsistent. Treatment that is effective for some, gives no relief to others. Insomnia has remained an enigma. Thanks to volunteers of the internet-platform slaapregister.nl there is now hope for faster discoveries.
Insomnia has many faces
With the help of thousands of volunteers, Drs. Tessa Blanken and her colleagues at the Netherlands Institute for Neuroscience now revealed why it has been so difficult to find consistent brain mechanisms and treatment effects. “While we have always considered insomnia to be one disorder, it actually represents five different disorders. Underlying brain mechanisms may be very different. For comparison: progress in our understanding of dementia was propelled once we realized that there are different kinds, such as Alzheimer-, vascular-, and frontal-temporal dementia.”
Five insomnia types
Surprisingly, the five insomnia types did not differ at all on sleep complaints like difficulty falling asleep versus early morning awakening. Some earlier attempts to define subtypes focused on these sleep complaints, and may therefore have been unsuccessful. Blanken and colleagues identified subtypes by looking beyond sleep complaints. They assessed dozens of questionnaires on personality traits that are known to be rooted in brain structure and function. Insomnia subtypes could be discovered by looking at trait profiles. Type 1 scores high on many distressing traits such as neuroticism and feeling down or tense. Types 2 and 3 experienced less distress and were distinguished by their high versus low sensitivity to reward. Type 4 and 5 experienced even less distress and differed by the way their sleep responded to stressful life events. These induced severe and long-lasting insomnia in type 4, while the sleep of type 5 was unaffected by these events .
Differences are not limited to traits
Volunteers measured again after five years mostly retained their own type, which suggested anchoring in the brain. Indeed, types also differed in their EEG response to environmental stimuli. Underlying mechanisms can now be better mapped with brain research. Subtyping was also clinically relevant. Effectiveness of treatment with sleeping pills or cognitive behavioral therapy differed per type. And the risk of developing a depression varied dramatically. Subtyping now enables much more efficient research into the prevention of depression, by inviting specifically those with the highest risk. The researchers now commenced a study into prevention of depression in people with insomnia that run the highest risk.
Source: Eus van Someren – KNAW
Publisher: Organized by NeuroscienceNews.com.
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Original Research: Abstract for “Insomnia disorder subtypes derived from life history and traits of affect and personality” by Tessa F Blanken, Jeroen S Benjamins, Denny Borsboom, Jeroen K Vermunt, Casey Paquola, Jennifer Ramautar, Kim Dekker, Diederick Stoffers, Rick Wassing, Yishul Wei, and Eus J W Van Someren in The Lancet Psychiatry. Published January 7 2019.
Insomnia disorder subtypes derived from life history and traits of affect and personality
Insomnia disorder is the second most prevalent mental disorder, and it is a primary risk factor for depression. Inconsistent clinical and biomarker findings in patients with insomnia disorder suggest that heterogeneity exists and that subtypes of this disease remain unrecognised. Previous top-down proposed subtypes in nosologies have had insufficient validity. In this large-scale study, we aimed to reveal robust subtypes of insomnia disorder by use of data-driven analyses on a multidimensional set of biologically based traits.
In this series of studies, we recruited participants from the Netherlands Sleep Registry, a database of volunteers aged 18 years or older, who we followed up online to survey traits, sleep, life events, and health history with 34 selected questionnaires of which participants completed at least one. We identified insomnia disorder subtypes by use of latent class analyses. We evaluated the value of our identified subtypes of insomnia disorder by use of a second, non-overlapping cohort who were recruited through a newsletter that was emailed to a new sample of Netherlands Sleep Registry participants, and by assessment of within-subject stability over several years of follow-up. We extensively tested the clinical validity of these subtypes for the development of sleep complaints, comorbidities (including depression), and response to benzodiazepines; in two subtypes of insomnia disorder, we also assessed the clinical relevance of these subtypes by use of an electroencephalogram biomarker and the effectiveness of cognitive behavioural therapy. To facilitate implementation, we subsequently constructed a concise subtype questionnaire and we validated this questionnaire in the second, non-overlapping cohort.
4322 Netherlands Sleep Registry participants completed at least one of the selected questionnaires, a demographic questionnaire, and an assessment of their Insomnia Severity Index (ISI) between March 2, 2010, and Oct 28, 2016. 2224 (51%) participants had probable insomnia disorder, defined as an ISI score of at least 10, and 2098 (49%) participants with a lower ISI score served as a control group. With a latent class analysis of the questionnaire responses of 2224 participants, we identified five novel insomnia disorder subtypes: highly distressed, moderately distressed but reward sensitive (ie, with intact responses to pleasurable emotions), moderately distressed and reward insensitive, slightly distressed with high reactivity (to their environment and life events), and slightly distressed with low reactivity. In a second, non-overlapping replication sample of 251 new participants who were assessed between June 12, 2017, and Nov 26, 2017, five subtypes were also identified to be optimal. In both the development sample and replication sample, each participant was classified as having only one subtype with high posterior probability (0·91–1·00). In 215 of the original sample of 2224 participants with insomnia who were reassessed 4·8 (SD 1·6) years later (between April 13, 2017, and June 21, 2017), the probability of maintaining their original subtype was 0·87, indicating a high stability of the classification. We found differences between the identified subtypes in developmental trajectories, response to treatment, the presence of an electroencephalogram biomarker, and the risk of depression that was up to five times different between groups, which indicated a clinical relevance of these subtypes.
High-dimensional data-driven subtyping of people with insomnia has addressed an unmet need to reduce the heterogeneity of insomnia disorder. Subtyping facilitates identification of the underlying causes of insomnia, development of personalised treatments, and selection of patients with the highest risk of depression for inclusion in trials regarding prevention of depression.