Shortened sleep may increase exercise-induced heart stress
In a new study, participants underwent a bout of intense exercise after normal sleep and after three nights of shortened sleep. When they exercised after shortened sleep, levels of troponin, a biomarker of heart damage, increased slightly more, compared to those who exercised in a well-rested state. The study is a small pilot study and it is not yet possible to determine whether the results may be relevant to cardiovascular health. The study is published in the journal Molecular Metabolism.
Previous epidemiological studies have demonstrated that at the population level, chronically disrupted and shortened sleep increases the risk of several cardiovascular diseases, such as high blood pressure and myocardial infarction. On the other hand, physical exercise can reduce the risk of cardiovascular disease. However, it is unknown whether controlled sleep restriction can modulate cardiac stress during intense exercise.
“Exercise is great for the heart, while lack of sleep can negatively impact the cardiovascular system. But it’s unclear whether shortened sleep can modulate the physiological stress intense exercise seems to have on cells. of the heart,” says Jonathan Cedernaes, a physician and associate professor of medical cell biology at Uppsala University, who led the study.
A specific type of troponin protein is found in the muscle cells of the heart. Low amounts of troponin may be released after high intensity training. Troponin levels are routinely determined in the clinic, as significantly higher levels are seen in acute cardiovascular events.
Higher troponin blood levels after exercise have been associated with a potential relative increased risk of cardiovascular disease. It is unclear what the mechanism is, but at the same time, it is known that a person’s cardiovascular health is modulated by an interaction of lifestyle factors. We therefore thought it would be important to investigate whether troponin release during exercise can be affected by sleep restriction. One reason is that many professions involve work that disrupts sleep, such as healthcare workers.”
Jonathan Cedernaes, Physician and Associate Professor of Medical Cell Biology, Uppsala University
Previous studies have shown that exercise can counteract some of the adverse effects of shortened sleep on metabolism. Additionally, population-level data indicate that exercise may counteract the negative effects of chronic sleep loss on the cardiovascular system.
“Those who report exercising regularly, but sleeping less than the ideal amount, still reduce their risk of dying from cardiovascular disease. At the same time, we know that chronic or recurring sleep disturbances are bad for cardiovascular health.It is therefore possible that more severe long-term sleep deprivation may increase the relative risk that the heart will be harmed in some way by more intense exercise.But many people suffer from temporary lack of sleep, and the need for sleep is also very individual, underlines Dr. Cedernaes Epidemiological evidence relating to sleep disorders per se applies mainly to chronic lack of sleep and long shift work. term, and are observed when averaging at the population level.
16 young men, in good health and of normal weight, participated in the study. All were thoroughly screened for previous cardiovascular disease, as well as the heredity of these conditions. Additionally, all participants had normal sleep patterns within the recommended range, i.e., they reported sleeping 7-9 hours on a regular basis.
The participants were followed in a sleep lab, where their meal and activity schedules were standardized. In one of the two sessions, the participants slept a normal amount, three nights in a row. During their other session, participants were kept awake for half the nights, three nights in a row. Each time, blood samples were taken in the evening and in the morning. After both sleep interventions, blood samples were also taken on the final day, before and after an intense 30-minute stationary bike session.
The researchers measured two biomarkers in the blood samples. NT-proBNP reflects the load on the heart. The second protein, troponin, is commonly used as a marker of heart damage. The results showed that NT-proBNP levels increased in response to exercise, but this increase did not differ based on sleep duration. Troponin blood levels also increased post-workout. However, for troponin, the post-exercise increase was almost 40% higher after three nights of partial sleep restriction, compared to after three nights of normal sleep.
“An important observation was that troponin and NT-proBNP levels were not elevated in response to sleep restriction at any time prior to training. It is possible that sleep deprivation may instead lower the threshold at which a Increased exercise load results in measurable stress in cardiac muscle cells, as can occur in response to intense exercise,” says Jonathan Cedernaes. “However, we noted that the increase in circulating troponin levels after exercise was variable among individuals. Previous research in resting conditions has also hinted at such variability, and it would be interesting to uncover the mechanisms.”
Jonathan Cedernaes continues:
“Today, there is no evidence to suggest that it is harmful to the heart to exercise regularly when you have had too little sleep. Instead, the argument can be turned around: by making sure you get enough sleep , the positive impact of physical exercise can be further increased.While we know that high-intensity training generally has long-term benefits, our results may be worth examining and exploring in specific groups of people. individuals. For example, athletes and the military. These groups may be required to perform at extreme physical levels even under conditions of shortened sleep. It may be worth further considering the importance of sleep in these contexts, d especially since we also know that improving sleep can also improve one’s performance, both cognitive and physical.
A limitation of the current study was that only 16 people were included. Jonathan Cedernaes points out that this should be considered a pilot study that requires further validation and follow-up. Such studies are also needed to examine whether these changes also apply to other age groups or to other women.
Martikainen, T. et al. (2022) Effects of reduced sleep on cardiac stress biomarkers after high-intensity exercise. Molecular metabolism. doi.org/10.1016/j.molmet.2022.101445.