Rest to Resist: How Sleep Fights Off Illness

Sleep is essential for the health and well-being of individuals across all age groups. It plays a crucial role in supporting cognitive function, emotional stability, mental health, and the health of cardiovascular, cerebrovascular, and metabolic systems. Sufficient sleep also helps reduce the risk of accidents and injuries, but how exactly does it affect the body?

Heart and circulatory system

When you fall asleep and enter non-REM sleep, your blood pressure and heart rate decrease, allowing your cardiovascular system to rest. During this phase, your parasympathetic nervous system (a network of nerves that helps the body relax and digest after stressful or dangerous situations) takes control, reducing the workload on your heart compared to when you are awake. As you transition into REM sleep and eventually wake, your sympathetic nervous system (a network of nerves that activates the body’s “fight-or-flight” response) becomes active, gradually increasing your heart rate and blood pressure to normal waking levels. However, a sudden spike in blood pressure and heart rate upon waking has been associated with an increased risk of angina (chest pain) and heart attacks. Chronic sleep deprivation or frequent nighttime awakenings can significantly impact your cardiovascular health and overall well-being. Insufficient sleep has been linked to an elevated risk of:

• Coronary heart disease
• High blood pressure (hypertension)
• Obesity, which can further strain the heart and circulatory system
• Stroke, due to the increased likelihood of blood clot formation or arterial damage

Immune system and respiratory system

When you sleep, your breathing becomes slower and shallower, reducing oxygen intake. While these changes are normal, they can pose challenges for individuals with respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD). Asthma symptoms often worsen during early morning sleep, and people with COPD may experience increased difficulty breathing at night. These disruptions highlight the interplay between sleep and respiratory health. Sleep also plays a crucial role in regulating your immune system, with different components becoming more active at various times of the day. For example, during sleep, certain immune cells become more active, enhancing your body’s ability to fight off infections. This explains why insufficient sleep can weaken your defenses, making you more prone to colds and other illnesses. Interestingly, when you’re battling an infection, your body naturally craves more sleep, yet the quality of your rest may suffer. Dr. Yvonne Chu, a sleep medicine specialist at the VA Connecticut Healthcare System, notes that acute illnesses often lead to reduced rapid eye movement (REM) sleep, the stage of sleep considered the most restorative. Poor sleep not only disrupts recovery during illness but also increases susceptibility to infections over time. Research shows that individuals who consistently get less than seven hours of sleep per night are three times more likely to catch the common cold compared to those who get eight or more hours regularly. Moreover, inadequate sleep can impair your response to vaccinations. Studies reveal that people who sleep less produce fewer antibodies to vaccines, including those for influenza and hepatitis A and B. In one study, participants who slept only four hours per night in the days surrounding vaccination developed significantly lower antibody levels than those with sufficient sleep.

Metabolism

The way your body processes fat is influenced by various circadian clocks, located in organs such as the liver, fat tissue, and muscles. These internal clocks help regulate metabolic functions, ensuring that your liver and other systems are primed to handle fats at optimal times of the day. Disrupting this natural rhythm by eating at unusual times can interfere with how your body metabolizes fat, potentially leading to metabolic imbalances.

Research has demonstrated that poor-quality or insufficient sleep can significantly impact your metabolism and contribute to weight gain. Key effects include:

• Altered hunger hormones: Sleep deprivation can disrupt the balance of hormones that regulate appetite, such as leptin (which suppresses hunger) and ghrelin (which stimulates hunger). This imbalance may lead to increased feelings of hunger and overeating.
• Impaired insulin sensitivity: Reduced sleep quality affects your body’s ability to respond effectively to insulin, a hormone critical for regulating blood sugar and fat storage.
• Increased cravings for unhealthy foods: Sleep loss is associated with greater consumption of fatty, sugary, and salty foods, which can further strain metabolic processes.
• Decreased physical activity: Fatigue resulting from poor sleep often leads to reduced energy levels and physical activity, compounding the risk of weight gain. *** Higher risk of metabolic syndrome: A combination of factors, including insulin resistance, high blood pressure, elevated cholesterol, and abdominal fat, can develop due to insufficient sleep.

Sources

• https://jcsm.aasm.org/doi/10.5664/jcsm.9476

• https://www.yalemedicine.org/news/how-sleep-affects-immunity

• https://www.nhlbi.nih.gov/health/sleep/why-sleep-important