People who have sleep apnea and spend less time in deep sleep may be more likely to have brain biomarkers that have been linked to an increased risk of stroke, Alzheimer’s disease and cognitive decline, according to new research published in the May 10, 2023, online issue of Neurology®, the medical journal of the American Academy of Neurology. The study does not prove that these sleep disturbances cause the changes in the brain, or vice versa. It only shows an association.
The study looked at sleep factors and biomarkers of the health of the brain’s white matter. The biomarkers measure how well the brain’s white matter is preserved, which is important to connect different parts of the brain. One of the biomarkers, white matter hyperintensities, are tiny lesions visible on brain scans. White matter hyperintensities become more common with age or with uncontrolled high blood pressure. The other biomarker measures the integrity of the axons, which form the nerve fibers that connect nerve cells.
“These biomarkers are sensitive signs of early cerebrovascular disease,” said study author Diego Z. Carvalho, MD, MS, of the Mayo Clinic in Rochester, Minnesota, and a member of the American Academy of Neurology. “Finding that severe sleep apnea and a reduction in slow-wave sleep are associated with these biomarkers is important since there is no treatment for these changes in the brain, so we need to find ways to prevent them from happening or getting worse.”
Sleep is one of the most essential human activities — so essential, in fact, that if we don’t get enough sleep for even one night, we may struggle to think, react, and otherwise make it through the day. Yet, despite its importance for function and survival, scientists still don’t fully understand how sleep works.
Enter Dragana Rogulja, a neurobiologist on a quest to unravel the basic biology of sleep.
As a self-described latecomer to science, Rogulja found herself drawn to questions she considers “broadly interesting and easy to understand on a basic human level.”
One of these questions…What happens when we sleep?
For Rogulja, an associate professor of neurobiology in the Blavatnik Institute at Harvard Medical School, an intriguing aspect of sleep is the loss of consciousness and awareness it brings, as the outside world disappears and the inner world takes over.
In a conversation with Harvard Medicine News, Rogulja delved into the details of her sleep research, which uses fruit flies and mice to explore why we need to sleep and how we disconnect from the world during sleep.
Harvard Medicine News: What are you studying in the context of sleep?
Rogulja: There are two main questions that my lab has been pursuing for the past several years. The first is why sleep is necessary for survival. Why is it that if you don’t sleep, you will literally die after not too long? The other question is how your brain disconnects from the environment when you fall asleep. How are stimuli prevented from reaching your brain during sleep? Elevating the threshold for sensory arousal is essential for sleep, and we want to understand how that barrier is built around the brain. Sleep is one unified state, but it seems to have multiple components that are regulated through separate mechanisms. We want to understand those mechanisms.
People who have sleep problems may be more likely to have a stroke, according to a study published in the April 5, 2023, online issue of Neurology®, the medical journal of the American Academy of Neurology.Sleep problems included getting too much or too little sleep, taking long naps, having poor quality sleep, snoring, snorting and sleep apnea. In addition, those who had five or more of these symptoms had an even greater risk of stroke. The study does not show that sleeping problems cause stroke. It only shows an association.
“Not only do our results suggest that individual sleep problems may increase a person’s risk of stroke but having more than five of these symptoms may lead to five times the risk of stroke compared to those who do not have any sleep problems,” said study author Christine Mc Carthy, MB, BCh, BAO, of University of Galway in Ireland. “Our results suggest that sleep problems should be an area of focus for stroke prevention.”
The international study involved 4,496 people, including 2,243 people who had a stroke who were matched to 2,253 people who did not have a stroke. The average age of participants was 62.
As our bodies and minds continue to adjust to the recent time change, debates continue around society about whether to make daylight saving time a permanent fixture, eliminate it or stay with the current semi-annual clock adjustment.
As those discussions continue, scientists at the University of California San Diego and their colleagues have made progress in understanding the circadian clock, the 24-hour cycle that synchronizes with light-dark exposure, and how it functions (scientists in circadian and sleep research recommend permanent standard time as the healthiest option when considering light and dark exposure).
Internal biological clocks exist throughout the tree of life, rhythmically influencing daily activities and behavior. Two years ago a multi-institutional team of researchers assembled a circadian clock in a test tube for the first time to probe the components of the clock’s rhythms and interactions.
The “In Vitro Clock” helped the researchers analyze how the components of the clock interact in different times of the daily circadian cycle to control gene expression.
A new study led by UC San Diego and UC Merced researchers has expanded on this foundation with the development of a method to study how the circadian clock synchronizes with the environment in real time. As described in the journal Proceedings of the National Academy of Sciences, real-time capability allowed them to explore deeper into the clock’s previously unknown internal functions, including how time-setting signals are transmitted from its core—known as the oscillator—to the expression of genes that ensure a properly functioning clock.