Overview of Insomnia


Charlene Gamadelo, MD, provides an overview of insomnia and discusses the prevalence by race and gender, the variations in presentation of symptoms in patients, and the pathways involved in sleep wakefulness cycles.

Charlene Gamadelo, MD: What’s the actual prevalence of insomnia in the United States? When we talk about insomnia as a symptom, it’s been recorded that 35% to 50% of people, if you pulled them off the street, would say they’re having insomnia symptoms. When it gets to the point that it’s a condition worthy of treatment consideration, 12% to 20% fulfill the criteria for insomnia. When we parse that out between women and men, it jumps up to 40% of women. Women are more than twice as likely to experience insomnia and be diagnosed with it than men. There are racial and ethnic differences in that presentation. It’s not clear in the research, in terms of an actual percentage, but it’s more prominent in Black, Indigenous, and people of color, particularly Black and Hispanic patients. Some reasons why we’re seeing that are because there’s a shorter sleep time among people of minoritized groups.

What are the different players of sleep, and how does the biology of women impact that? That continues to be an ongoing pursuit of research. How we sleep, why we sleep, and how sleep is different between the genders continue to have unanswered questions. We know that between wake and sleep, certain regions of the brain send out signals that are responsible for staying awake and going to sleep. When it comes to the orchestration of staying awake, many chemicals are related to that. This includes dopamine, norepinephrine, and serotonin, but the biggest conductor appears to be orexin. Different centers of the brain are responsible for releasing those hormones.

On the flip side, there are a few chemicals in certain areas of the brain responsible for the sleep state, particularly GABA [gamma-aminobutyric acid], galanin, and adenosine. These chemicals are sometimes the targets of medicines we see on the market. But the way the sleep-wake state happens is that these different regions turn up and turn down the release of those chemicals. It’s like a switch or a balance. Once it switches to the higher level, where more of the sleep chemicals are on board, it flips the switch and we go to sleep. Then gradually, overnight that balance starts to teeter. When there’s a magic threshold with more wake chemicals floating in the brain, we flip over to the wake state. We understand it as a flip switch between sleep and wake.

As mentioned, women suffer from insomnia more than men, and there are certain hormonal reasons behind that. But it remains unclear how those hormones or the hormonal state with women exactly and directly impacts that flip switch.

Transcript edited for clarity

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