Sleep apnea is a condition where breathing repeatedly stops and starts during sleep. These interruptions, called apneas or hypopneas, can last for ten seconds or longer and often lead to reduced oxygen levels in the blood and fragmented sleep. While snoring is a common symptom, sleep apnea is much more than just a noisy night; it is a serious sleep disorder that can significantly impact overall health if left untreated. Estimates suggest that obstructive sleep apnea, the most common type, affects as much as 20% of the population, with a large percentage remaining undiagnosed.
Cardiovascular System Impacts
Sleep apnea can significantly impact the cardiovascular system, contributing to several serious conditions. High blood pressure, or hypertension, is a common secondary condition, affecting about half of individuals with obstructive sleep apnea. During apneic episodes, blood pressure surges, particularly at night, and can remain elevated even during the day. This sustained elevation is linked to increased sympathetic nervous system activity, inflammation, and oxidative stress, which can damage blood vessels and lead to sustained daytime hypertension. Additionally, the natural nocturnal blood pressure dip often seen in healthy individuals may be absent in those with sleep apnea, further increasing hypertension risk.
Sleep apnea also increases the risk of heart disease, including coronary artery disease, heart attack, and heart failure. The repeated changes in intrathoracic pressure from unsuccessful breathing efforts can damage the heart over time. Sleep apnea increases the risk of heart failure by 140% and coronary heart disease by 30%.
Individuals with sleep apnea face an increased risk of stroke, with a 60% higher risk observed. This heightened risk is attributed to mechanisms such as atherosclerosis, hypercoagulability, and vascular endothelial dysfunction. Sleep apnea is also associated with irregular heart rhythms, such as atrial fibrillation. People with sleep apnea are two to four times more likely to develop atrial fibrillation due to chest pressure changes and stress from breathing interruptions.
Metabolic and Organ Health
Sleep apnea also significantly affects metabolic processes and other organs beyond the heart. There is a strong link between sleep apnea and Type 2 Diabetes, with over half of Type 2 Diabetes patients also experiencing sleep apnea. Intermittent hypoxia, a characteristic of sleep apnea, can lead to insulin resistance, where the body’s cells do not respond effectively to insulin, resulting in elevated blood sugar levels.
This disruption of sleep patterns and repeated oxygen deprivation can activate the sympathetic nervous system and increase inflammatory cytokines, contributing to impaired glucose metabolism. The severity of sleep apnea is associated with poorer glycemic control in individuals with Type 2 Diabetes.
Non-Alcoholic Fatty Liver Disease (NAFLD) is another significant secondary condition linked to sleep apnea. Its presence and severity are closely associated with sleep apnea. Intermittent hypoxia, a hallmark of sleep apnea, plays a role in NAFLD’s development and progression by promoting insulin resistance, oxidative stress, and lipid metabolism impairment.
Sleep apnea can enhance adipose tissue lipolysis, leading to increased free fatty acids in the bloodstream, which promotes fat accumulation in the liver. This can also lead to hepatic inflammation and steatosis, key features of NAFLD. An altered gut-liver axis, characterized by increased intestinal permeability, may also contribute to NAFLD progression.
Brain and Mental Well-being
Sleep apnea significantly affects brain function and mental health. Individuals often experience excessive daytime fatigue, which can impair concentration and lead to memory problems. Chronic sleep deprivation and fluctuating oxygen levels impact cognitive function, affecting areas like executive functions, attention, and working memory.
Hypoxia associated with sleep apnea can cause changes in brain regions such as the hippocampus and right frontal cortex, with neuroimaging studies revealing hippocampal atrophy in some individuals. This can lead to difficulties in mentally manipulating non-verbal information and overall cognitive decline. Untreated sleep apnea can increase the risk of developing mild cognitive impairment, which may be a precursor to dementia.
Beyond cognitive issues, sleep apnea can exacerbate or contribute to mood disorders such as depression and anxiety. The symptoms of sleep apnea and depression can overlap, making diagnosis challenging. A bidirectional relationship exists, meaning each condition can increase the likelihood of the other.
Morning headaches are also a common symptom for individuals with sleep apnea, potentially due to changes in blood gas levels that cause blood vessels to widen and increase pressure within the skull. Frequent awakenings during the night, which disrupt sleep quality, can also trigger or worsen headaches and migraines.
Anesthesia and Medication Considerations
Individuals with untreated sleep apnea face increased risks when undergoing surgery, particularly concerning anesthesia and certain medications. Anesthetic agents, especially general anesthesia, can slow breathing and increase sensitivity to their effects, making it more challenging to regain consciousness and breathe independently after a procedure. These medications, along with sedatives and pain medications like opioids, can further depress the body’s ventilatory response and impair the natural arousal response that helps overcome airway obstruction.
The increased collapsibility of the upper airway during sedation or anesthesia can worsen sleep apnea, increasing the risk of complications such as hypoxemia, pneumonia, and cardiac arrhythmias post-surgery. Many patients with sleep apnea are undiagnosed before surgery, making it important to inform healthcare providers about any suspected sleep apnea symptoms. Providers can then take precautions, such as closer monitoring during and after surgery, and selecting specific anesthesia medications to minimize risks.