Obstructive sleep apnea (OSA) affects far more than your sleep. It increases your risk of heart disease, stroke, diabetes, and dementia if left untreated.Each night, the repeated breathing interruptions that occur during OSA can trigger stress hormones, keep your blood pressure and heart rate elevated, and interfere with blood sugar control, putting long-term strain on your body. When you understand these connections, you and your doctor can find the best treatment for your OSA with your long-term health in mind.

OSA causes the release of stress hormones during sleep, when your body is seeking rest and recovery, says Raj Dasgupta, MD, a pulmonary critical care and sleep medicine specialist at Huntington Health, a Cedars-Sinai affiliate, in Pasadena, California.

“Instead of sleep being restorative, sleep apnea causes repetitive physiological stress, which accelerates cardiovascular, metabolic, and neurological disease,” says Priya Jaisinghani, MD, who specializes in endocrinology, obesity medicine, and diabetes at NYU Langone Health in New York City.

Over time, these nightly stress responses can cause numerous health issues, including the following.

• Intermittent Low Oxygen Also called hypoxia, this drop in oxygen levels occurs each time your breathing stops when you sleep. This creates a cycle of increases and decreases in your blood-oxygen levels that leads to oxidative stress, a buildup of harmful molecules that can damage blood vessels, strain your heart, and put you at greater risk of disease.

• Sympathetic Surges The breathing disruptions that OSA causes during sleep activate your sympathetic nervous system, which controls your “fight or flight” responses. These increase your blood pressure and heart rate, which otherwise naturally slow down during sleep.

• Intrathoracic Pressure Swings Struggling to breathe through a blocked airway puts physical strain on your chest and heart walls. “If you’re not getting air through the upper airway, your chest wall will have to work harder; your heart has to work harder,” Dr. Dasgupta says.

• Sleep Fragmentation Your sleep might be interrupted hundreds of times each night with OSA, which can leave you tired the next day. This pattern also interrupts your sleep cycles, preventing you from getting the type of sleep that helps your brain, heart, and immune system recharge.

If your OSA is untreated or undertreated, nightly breathing disturbances can put serious strain on your heart and blood vessels. Over time, this chronic strain that stress responses cause may lead to a number of serious heart conditions, including:

• Resistant Hypertension High blood pressure (hypertension) that doesn’t go down with treatment is called resistant hypertension. Having OSA can increase your risk of this type of hypertension fivefold, and as many as 80 percent of people with resistant hypertension also have OSA. Factors such as hypoxia, consistent elevated blood pressure, and chronic inflammation lead to this condition.

• Left Ventricular Hypertrophy High blood pressure and OSA can lead to this condition, in which your heart muscles thicken. It also increases your risk of blood clots, heart attack, and heart failure.

• Arrhythmias Fluctuations in oxygen and pressure can “rewire” the heart’s electrical system, increasing the risk of irregular heartbeats and heart-rhythm conditions known as arrhythmias. These arrhythmias can affect blood pressure and even lead to sudden death if you have heart disease.

• Stroke Low oxygen levels and high blood pressure from OSA also can increase your risk of stroke. As many as 70 percent of people who have had a stroke also have sleep apnea, and OSA increases your risk of a first stroke.

• Heart Failure OSA is one of the most common conditions linked to heart failure, with as many as 60 percent of people with heart failure also having untreated sleep apnea. It also is linked to a higher probability of repeat hospitalization and death.

Sleep interruptions from OSA also disrupt how your body handles food and energy. This makes it harder to lose weight and easier to gain weight, Dr. Jaisinghani says, leading to a cycle with negative effects.

“Excess weight worsens airway collapse, while untreated OSA makes weight management and glycemic control significantly more difficult,” she says.

This is why obesity and OSA are closely correlated, with one leading to the other. Sleep disorders such as OSA cause changes to your levels of the hormones leptin, which tells your brain when you are full, and ghrelin, which tells you when you are hungry.

“The satiety hormone leptin falls, and the hunger hormone ghrelin rises, leading to potential hunger, cravings, and weight gain,” says Jaisinghani, adding that daytime fatigue from OSA also makes it harder to lose weight via activity and exercise.

In addition to affecting these hormones, OSA can cause dangerous changes to your blood sugar. Sleep interruptions cause your brain to release cortisol, which raises your blood sugar. Left untreated over time, this can lead to insulin resistance, in which your body struggles to process sugar properly, a root cause of type 2 diabetes.

With OSA making it harder to manage your weight and blood sugar, it also puts you at a much higher risk of developing type 2 diabetes. As many as 80 percent of people with type 2 diabetes also have OSA, and the worsening effects of one can cause complications in the other.If you’ve been diagnosed with OSA, it may have come after a diabetes diagnosis. Doctors often recommend testing for OSA if you have diabetes or hypertension, as untreated OSA can make either condition harder to control.

OSA can increase your risk of other metabolic health conditions associated with diabetes and obesity, including:

• Liver Disease About half of people with OSA have metabolic dysfunction–associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease. Severe, untreated OSA also may lead to more severe MASLD.

• Kidney Disease Among people with early chronic kidney disease, 31 percent also have OSA. The number increases to 45 percent among people with more severe kidney disease.

Untreated OSA can change how your brain functions, making it harder for brain cells to make connections and even shrinking parts of your brain that are responsible for making memories. It all comes down to the sleep you may be losing.

“Deep sleep and REM sleep are very important to help out with cognition, your mood, and memory,” Dasgupta says.

When you don’t get enough sleep at these stages, it reduces the time your body has to repair itself and clean out proteins that have built up. Accumulating too much of the amyloid protein, for instance, can lead to dementia and Alzheimer’s disease, Dasgupta says.Other cognitive issues that may arise from OSA include:

• Decreased attention and concentration

• Impaired motor skills

• Poor memory

• Movement issues and Parkinson’s disease

OSA treatment doesn’t just improve your sleep. It also reduces your risk of chronic disease.

The most common OSA treatment is continuous positive airway pressure (CPAP) therapy. A CPAP machine uses a steady flow of pressurized air to keep your airway open during sleep.

Using CPAP for at least four hours each night can lower your risk of heart-related death by as much as 55 percent. CPAP use can also reduce the risk of type 2 diabetes and improve insulin sensitivity, though it’s necessary to stick with the treatment long-term.Your doctor may also prescribe tirzepatide (Zepbound), which the U.S. Food and Drug Administration has approved to treat moderate to severe OSA in people with obesity. Tirzepatide does not improve your sleep on its own, as CPAP treatment can. But it can address some of the root causes of OSA by helping you lose fat around your chest and neck. This may reduce OSA symptoms such as breathing disruptions and improve lung capacity.

“Weight-management medications such as tirzepatide can meaningfully reduce disease burden and in some situations even reverse disease state,” Jaisinghani says. “This is particularly helpful for patients who are unable to tolerate other treatment options such as the CPAP.”

Although there is no data yet on long-term tirzepatide use, preliminary analyses show that it can significantly reduce cardiometabolic risk factors — including blood pressure, cholesterol, and insulin resistance — in people with OSA.

• The sleep disorder obstructive sleep apnea (OSA) can cause hundreds of sleep interruptions each night. These can add up to short- and long-term health issues if your OSA is left untreated.

• By interrupting your sleep cycles, OSA reduces your blood-oxygen levels, causes your fight-or-flight systems to activate, and puts strain on your heart and other organs.

• OSA can lead to heart conditions such as high blood pressure, arrhythmias, and heart failure, as well as type 2 diabetes and cognitive issues.

• Treating your sleep apnea isn’t just about getting a better night of sleep — it can reduce your risk of chronic disease.