It’s been long-accepted that sleep plays a crucial part in human development and well-being. While we are unconscious, we are far from inactive, with our brain working to lower cancer risk and promote memory storage, among other things. Though past research has shown that a lack of sleep increases the risk of developing heart disease, researchers were unsure of its effects on a cellular level. Recent research by the Harvard Medical School, however, has shed some light on the mechanisms relating insufficient sleep to cardiovascular disease. By using mice as models, scientists were able to find biological mechanisms underlying atherosclerosis that were exacerbated when mice were disrupted in their sleep.
Image source: Jamie Grill
Atherosclerosis is a disease that affects the arteries. It starts when fat cells and cholesterol collect in the arterial wall. The body treats the built-up material as an invader and initiates an immune response, which results in inflammation and further plaque development over several decades. Eventually, the clot can break off and block blood flow to the heart, resulting in a heart attack. To study the relationship between sleep and heart disease, researchers split mice into two groups. One group was allowed to sleep normally. Another group was periodically disrupted as they slept. After a few weeks, the scientists studied the mice to find differences across the two groups.
One of the most interesting differences they discovered was that the mice with interrupted sleep produced less hypocretin. Hypocretin is a chemical produced in the hypothalamus, which is part of the brain. A decrease in hypocretin is most often associated with narcolepsy, but through their research, the scientists discovered that hypocretin was associated with the development of heart disease as well. Specifically, a decrease in hypocretin caused an increase in the production of monocytes and neutrophils, two types of cells found in the immune system that cause the inflammation linked to atherosclerosis. The production of these cells is regulated by a compound called CSF-1. When hypocretin decreased, CSF-1 increased in response, stimulating the production of the aforementioned immune cells. Ultimately, the researchers found that the sleep-deprived mice had more frequent and more severe cases of atherosclerosis in their arteries than the mice that were allowed to sleep normally.
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The links that the researchers from Harvard Medical School discovered are crucial and timely. Though the recommended amount of sleep for adults aged 18-60 is 7 hours a night, a study conducted by the CDC showed that more than one-third of adults slept less than the recommended amount. Aside from effects such as weight gain and fatigue, people who don’t sleep enough are at higher risk of developing heart disease, the leading cause of death in America. Despite the many unanswered questions about sleep, the discoveries made by the scientists at Harvard Medical School contribute to the ever-growing pool of knowledge about the importance of sleep for our physical and mental well-being.
Feature Image Source: Claudio Scott
