Identification of Neuro-Immune Axis: Good Sleep Protects Against the Risk of Heart Diseases

New study in mice shows that getting enough sleep every night could provide protection from cardiovascular diseases

Getting enough sleep is a general advice given by doctors as it is associated with maintaining good health. When someone gets adequate sleep, they feel energized and fresh to start their day and lack of enough sleep increases risk of illnesses. Lack of sleep is now a health problem affecting people of all ages and gender. Many studies have been conducted on animals and humans to understand benefits of sleep. Sleep is thought to play an important role in our immunity, memory, learning etc. Sufficient sleep is also considered important to maintain our cardiovascular health by controlling risk of clogged arteries which can lead to heart attack or stroke. Cardiovascular diseases are the leading cause of deaths worldwide. 85 percent of cardiovascular deaths occur due to heart attack or stroke. Conditions like hypertension or diabetes increase risk of cardiovascular diseases. People who have or are at risk of cardiovascular diseases require early detection and management to keep adverse events at bay. Many cardiovascular diseases are preventable by lifestyle changes like healthy diet, exercise, avoiding tobacco and alcohol.

Association between sleep and cardiovascular diseases in mice

Arteries – our blood vessels – transport oxygen and nutrients from our heart to rest of the body. When our arteries become narrow because of plaque build-up (fatty acids deposits), the condition is called atherosclerosis (or hardening of the arteries) making arteries more prone to rupture. A new study published in Nature aimed to understand the association between sleep or rather lack of sleep and cardiovascular diseases via exploring a new pathway for atherosclerosis. Researchers have described a mechanism that lack of enough sleep can escalate production of inflammatory white blood cells (WBCs) which are the biggest contributors towards a person developing atherosclerosis as they contribute towards plaque growth. In the experiment, mice were genetically engineered to develop atherosclerosis as these animals were genetically prone to artery plaque. Mice were subjected to constant interruptions in their sleep through noise or discomfort every 2 minutes during their necessary 12-hour sleep interval. As a result, these sleep-deprived mice who underwent 12 weeks of disturbed sleep developed bigger arterial plaques and also higher number of inflammatory cells like monocytes and neutrophils compared to mice who had normal sleep. Plaque build-up led to atherosclerosis in their blood vessels. Also, there was two-fold increase in production of immune cells in bone marrow giving rise to more WBCs. No changes were seen in weight gain, cholesterol or glucose tolerance levels

Researchers also identified a hormone in brain called hypocretin which is known to regulate sleep and wakefulness since it is seen in high levels when animals or humans are awake. This hormone, produced by signalling molecule hypothalamus, was found to regulate production of WBCs in bone marrow by interacting with neutrophil progenitors. Neutrophils induce monocyte production by releasing a protein called CSF-1. The mice who were lacking the gene for this protein confirmed that hormone hypocretin controls CSF-1 expression, production of monocytes and development of plaque in arteries. The levels of this hormone were significantly reduced in sleep-deprived mice which led to increased CSF-1 production by neutrophils, increased monocytes and thus advanced atherosclerosis. Therefore, hypocretin hormone is an important inflammatory mediator seen to play a critical role in protection from cardiovascular diseases.

This study will need to be extended in humans (because mice and human sleep patterns may not be identical) before hypocretin can be used therapeutically. It is possible that sleep is directly responsible for regulation of inflammatory cells in bone marrow and for the overall health of our blood vessels. Lack of enough sleep affects this control of inflammatory cells production which can lead to higher inflammation and more heart illnesses. It may happen even if other risk factors like obesity and hypertension are controlled. Understanding underlying mechanisms of how sleep affects human health can help to devise new therapies.



McAlpine CS et al. 2019. Sleep modulates haematopoiesis and protects against atherosclerosis. Nature 566.

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