Sleep, Gender, and Mental Health.
NIH-hosted panel addresses the interconnections
WASHINGTON — Differences in how men and women sleep could explain differences in the neuropsychiatric illnesses they develop, and potentially influence treatment, explained Ruth Benca, MD, PhD, professor and chair of psychiatry and human behavior at the University of California Irvine, at a conference on sleep hosted by the National Institutes of Health.
If a patient presents with a sleeping problem, there’s a strong chance he or she has a psychiatric disorder as well, Benca said at the 2018 Research Conference on Sleep and the Health of Women on Tuesday.
Epidemiological evidence shows certain neurological or neuropsychiatric disorders are more common among men than women. For example schizophrenia is more common in men and Alzheimer’s disease is more common in women, Benca said.
At the meeting, Benca pondered whether differences in how men and women sleep affect development of these disorders.
“It’s actually surprising how little we know,” Benca said, given how much sleep research there’s been in humans and animals.
There is some evidence that women get more sleep than men — which is controversial — but what’s been found more consistently is that women have more slow wave activity (a stage 3 sleep phenomenon) in the prefrontal region than men, and more stage 2 spindle activity, Benca said.
However, the reasons for these differences aren’t clear, she said.
Women also tend to go to sleep earlier and wake up earlier than men, have higher rates of insomnia and restless leg syndrome, and lower rates of sleep apnea, Benca noted.
In looking at particular sleep disturbances and their relationship with psychiatric disorders, Benca spotlighted findings in three areas: depression, schizophrenia, and Alzheimer’s disease.
Depression and Insomnia
Chronic insomnia is highly predictive of developing depression, Benca said, noting that those with insomnia are 2.5 times as likely to develop depression, compared to people without sleep problems.
This is not a trivial connection, Benca stressed, since depression is the leading cause of disability worldwide. Also, women have twice the rates of depression as men, she said.
This, of course, begs the question of whether women are more likely to get depressed because of their higher risk for insomnia. But regrettably, said Benca, very few studies look at sex differences in depression.
There has been some research to suggest a “dramatic increase” in slow wave activity in depressed women compared to depressed men who did not show any significant difference. (Women who aren’t depressed already show more slow wave activity than men who aren’t depressed, she clarified.)
While it’s not clear what these differences mean, some of this slow wave activity has been linked to some features of depression, Benca noted.
Also, a handful of studies focused on people with major depression and insomnia have shown that treating insomnia and depression, using either medication or cognitive behavioral therapy for insomnia, can more rapidly improve depression, Benca said. But whether treating insomnia can actually prevent depression or other mood disorders is still not certain, she added.
“In terms of clinical practice, we recommend that insomnia needs to be a target of treatment along with specific treatment for depression in patients with mood disorders,” Benca wrote.
Insomnia is associated with a 1.5-fold greater risk of Alzheimer’s disease. Women have higher rates of insomnia especially after menopause. Women also have higher rates of Alzheimer’s disease — about two-thirds of patients with Alzheimer’s are women — Benca noted.
Alzheimer’s disease is thought to be caused by an accumulation of amyloid plaque and tau protein tangles in the brain. Amyloid protein is cleared from the brain during sleep. In studies that use self-reported measures of sleep, poor sleep was found to be linked to greater amyloid load, Benca explained.
Another wrinkle is that chronic inflammation has been found to “promote” the pathology of Alzheimer’s and sleep loss can increase neuroinflammation.
These connections, for Benca, bring up another question: Could insomnia be contributing in a causal way to these higher rates of Alzheimer’s disease in women?
In her presentation, Benca also considered the connections between sleep and schizophrenia. The rate of schizophrenia in men is 1.4 times higher than in women, she said. Not only do more men have the disease than women, they also begin to develop the disease sooner and respond less well to medication. But sex-linked genetic risk has not been found in schizophrenia, Benca said.
Curiously, said Benca, “people with schizophrenia tend to lose their sleep spindles.” First-degree relatives of people with schizophrenia also seem to show deficits in spindle activity, Benca said. And some research has found increasing spindle activity with medication improves cognitive function in people with schizophrenia, she said.
That women have more sleep spindles than men led Benca to more questions. Could women be protected from schizophrenia due to their higher rates of sleep spindles? Can a paucity of these spindles help identify people with schizophrenia?
Clearly, more research is needed, Benca concluded.
The 2018 Research Conference on Sleep and the Health of Women is a collaborative program from the National Center on Sleep Disorders Research (NCSDR) of the National Heart, Lung, and Blood Institute (NHLBI), the NIH Office of Research on Women’s Health, and the Health and Human Services Office on Women’s Health as well as members of the trans NIH Sleep Research Coordinating Committee and other federal agencies.