Irregular sleep patterns, such as inconsistent bedtimes or frequent disruptions during sleep, have been linked to a variety of negative health outcomes, including an increased risk of cardiovascular disease. Here are some potential reasons why irregular sleep may be harmful to your heart:
- Disruption of circadian rhythms: Irregular sleep patterns can disrupt the body’s internal clock, known as the circadian rhythm. This can lead to changes in the production of hormones that regulate blood pressure, inflammation, and glucose metabolism, all of which can have negative effects on cardiovascular health. For example, studies have found that night shift workers, who often have irregular sleep schedules, have an increased risk of developing cardiovascular disease (1, 2).
- Increased inflammation: Sleep disruption can lead to an increase in systemic inflammation, which is associated with an increased risk of cardiovascular disease. Studies have found that people who experience poor sleep quality or insomnia have higher levels of inflammatory markers in their blood (3, 4).
- Disruption of blood pressure: Irregular sleep patterns can disrupt the normal fluctuations in blood pressure that occur during sleep. For example, people who have sleep apnea, a condition characterized by frequent disruptions in breathing during sleep, often experience spikes in blood pressure. Over time, these spikes can damage the walls of blood vessels and increase the risk of cardiovascular disease (5, 6).
- Insulin resistance: Irregular sleep patterns can also lead to insulin resistance, a condition in which the body’s cells become less responsive to insulin, a hormone that helps regulate blood sugar. Insulin resistance is a risk factor for type 2 diabetes, which is itself a risk factor for cardiovascular disease (7, 8).
Circadian rhythms are biological processes that follow a roughly 24-hour cycle and regulate many of our physiological and behavioral functions. The word “circadian” comes from the Latin words “circa,” meaning “around,” and “diem,” meaning “day.” These rhythms are driven by an internal biological clock that is located in a part of the brain called the suprachiasmatic nucleus (SCN), which is located in the hypothalamus.
The SCN receives information about light and dark cycles from the eyes, and uses this information to synchronize the body’s internal clock with the external environment. This synchronization is known as entrainment. In addition to light, other factors such as temperature, feeding and exercise schedules, social interactions, and medications can also affect circadian rhythms.
Circadian rhythms influence a wide range of biological processes, including:
- Sleep-wake cycle: Circadian rhythms help regulate the timing of sleep and wakefulness. The internal clock promotes wakefulness during the daytime and promotes sleepiness at night.
- Hormone production: The release of many hormones, including cortisol, melatonin, and growth hormone, follows a circadian rhythm.
- Body temperature: The body’s core temperature follows a circadian rhythm, with a minimum at night and a maximum in the late afternoon.
- Metabolism: The body’s metabolism is influenced by circadian rhythms, with some processes such as glucose metabolism and fat storage being more active during the day.
- Cognitive performance: Circadian rhythms can influence cognitive performance, with some studies suggesting that performance on tasks requiring attention and memory may be better during the day than at night.
Disruptions to circadian rhythms, such as those caused by jet lag, shift work, or sleep disorders, can have negative effects on health, including an increased risk of cardiovascular disease, metabolic disorders such as obesity and diabetes, and mental health disorders such as depression and anxiety. It is important to maintain regular sleep and wake times and to expose oneself to natural light during the day to support healthy circadian rhythms.
Insulin resistance is a condition in which the body’s cells become less responsive to insulin, a hormone produced by the pancreas that helps regulate blood sugar levels. As a result, the body needs to produce more insulin to keep blood sugar levels within a normal range. Over time, this can lead to high blood sugar levels and an increased risk of developing type 2 diabetes.
Several factors can contribute to the development of insulin resistance, including:
- Genetics: Insulin resistance tends to run in families, suggesting that there may be a genetic component to the condition. Some genetic mutations can impair insulin signaling and contribute to insulin resistance.
- Obesity: Being overweight or obese is a significant risk factor for insulin resistance. Excess body fat, particularly around the abdomen, can lead to the release of inflammatory molecules that interfere with insulin signaling.
- Sedentary lifestyle: Lack of physical activity can contribute to the development of insulin resistance. Exercise helps to improve insulin sensitivity, allowing the body to use insulin more effectively.
- Poor diet: A diet that is high in refined carbohydrates, such as sugar and white flour, can lead to rapid spikes in blood sugar levels and contribute to insulin resistance over time. A diet that is low in fiber and high in saturated and trans fats can also contribute to insulin resistance.
- Sleep disruption: Sleep disruption, such as that caused by sleep apnea or shift work, can contribute to insulin resistance by disrupting circadian rhythms and altering the body’s hormonal balance.
- Chronic stress: Chronic stress can increase levels of cortisol, a hormone that can interfere with insulin signaling and contribute to insulin resistance.
While insulin resistance is a risk factor for type 2 diabetes, not everyone with insulin resistance will develop diabetes. Lifestyle changes, such as losing weight, increasing physical activity, and improving dietary habits, can help to improve insulin sensitivity and prevent the development of type 2 diabetes. In some cases, medications such as metformin may also be prescribed to improve insulin sensitivity.
Several studies have found associations between irregular sleep patterns and cardiovascular disease. For example, a large study of middle-aged adults found that those with the most irregular sleep patterns had a higher risk of developing cardiovascular disease over a 5-year period, even after controlling for other risk factors such as age, sex, and BMI (9). Another study found that people who reported poor sleep quality had a higher risk of developing heart disease over a 14-year period (10).
In summary, irregular sleep patterns can have negative effects on the cardiovascular system through a variety of mechanisms, including disruption of circadian rhythms, increased inflammation, disruption of blood pressure, and insulin resistance. If you are experiencing irregular sleep, it may be worth talking to your healthcare provider about strategies to improve your sleep habits.
- Vyas MV, Garg AX, Iansavichus AV, et al. Shift work and vascular events: systematic review and meta-analysis. BMJ. 2012;345:e4800.
- Vetter C, Devore EE, Wegrzyn LR, et al. Association between rotating night shift work and risk of coronary heart disease among women. JAMA. 2016;315(16):1726-1734.
- Irwin MR, Olmstead R, Carroll JE. Sleep disturbance, sleep duration, and inflammation: a systematic review and meta-analysis of cohort studies and experimental sleep deprivation. Biol Psychiatry. 2016;80(1):40-52.
- Patel SR, Zhu X, Storfer-Isser A, et al. Sleep duration and biomarkers of inflammation. Sleep. 2009;32(2):200-204.
- Drager LF, Polotsky VY, Lorenzi-Filho G. Obstructive sleep apnea: an emerging risk factor for atherosclerosis. Chest. 2011;140(2):534-542.
- Somers VK, White DP, Amin R, et al. Sleep apnea and cardiovascular disease: an American Heart Association/american college of card