Obstructive sleep apnea is closely linked to high blood pressure, atrial fibrillation, heart failure and stroke. It is very common in people who already have heart disease and often goes undiagnosed.
What treatment does for the heart is a separate question, and the answer is more limited than many people assume. CPAP reliably improves sleepiness and quality of life and lowers blood pressure a little in people whose pressure is uncontrolled. Large trials have not shown that it prevents heart attacks or strokes.
Key takeaways
- Sleep apnea is common in midlife and far more common among people with high blood pressure, atrial fibrillation or heart failure.
- The more severe the apnea, the higher the odds of developing high blood pressure in the following years.
- In the largest randomized trial, CPAP did not reduce cardiovascular events, though it improved symptoms and quality of life.
- Pooled trial data hint at benefit in people who use CPAP at least four hours a night, but that finding is not proof.
- Treating sleep apnea does not replace managing blood pressure, cholesterol and blood sugar.
What sleep apnea is and how common it is
In obstructive sleep apnea the upper airway narrows or closes repeatedly during sleep. Each episode briefly lowers blood oxygen, triggers a surge from the nervous system and breaks up sleep. Severity is measured by the apnea-hypopnea index, or AHI: the number of these events per hour.
A 2021 scientific statement from the American Heart Association estimates that about 34% of middle-aged men and 17% of middle-aged women meet the criteria for obstructive sleep apnea.1 Among people with high blood pressure, heart failure, coronary artery disease, atrial fibrillation or stroke, the figure is as high as 40% to 80%.1
The same statement says sleep apnea is often underrecognized and undertreated in cardiovascular care. It is also more common with excess weight, a topic covered in our guide to visceral fat and heart risk.
The link to blood pressure
Blood pressure is the best documented connection. The Wisconsin Sleep Cohort Study measured breathing during sleep in 709 adults and checked their blood pressure four years later.
Compared with people who had no breathing events, those with an AHI of 5 to 14.9 had about twice the odds of high blood pressure at follow-up, and those with an AHI of 15 or more had nearly three times the odds.2 The result held after adjusting for body size, age, sex, alcohol and smoking.
That stepwise pattern, with more apnea followed by more hypertension, is why researchers regard sleep apnea as a likely cause of high blood pressure and not just a companion to it.
Heart rhythm and other heart conditions
A 2022 American Heart Association statement on sleep-disordered breathing and arrhythmias concluded that strong evidence implicates it in abnormal heart rhythms, including atrial fibrillation.
The statement is careful about treatment. Observational studies suggest that treating sleep apnea reduces the return of atrial fibrillation after a rhythm procedure, but high-level evidence from clinical trials is not available.3
For this reason the 2021 statement recommends screening for sleep apnea in people with resistant or poorly controlled high blood pressure and in people whose atrial fibrillation returns after cardioversion or ablation.1
What CPAP trials did and did not show
CPAP, or continuous positive airway pressure, keeps the airway open with gentle air pressure through a mask. Because sleep apnea is tied to so many heart problems, researchers expected that treating it would prevent them. The largest test of that idea was the SAVE trial.
SAVE enrolled 2,717 adults aged 45 to 75 who had moderate-to-severe obstructive sleep apnea and established coronary or cerebrovascular disease. They were randomly assigned to CPAP plus usual care or to usual care alone. After an average of 3.7 years, a serious cardiovascular event had occurred in 17.0% of the CPAP group and 15.4% of the usual-care group, a difference that was not statistically significant.4
CPAP did work on other measures. It significantly reduced snoring and daytime sleepiness and improved health-related quality of life and mood.4
Two features of the trial are worth knowing. Participants used CPAP for an average of 3.3 hours a night, and all of them already had cardiovascular disease, so the trial does not tell us about preventing a first event.
A 2023 analysis combined individual data from SAVE and two similar trials, 4,186 participants in all. Overall, CPAP again made no difference to repeat cardiovascular events. In a separate analysis of people who used CPAP at least four hours a day, good adherence was associated with a 31% lower risk.5 People who use CPAP faithfully may differ in other ways, so this result suggests a possibility and does not settle it.
On blood pressure, a pooled analysis of 36 trials with 9,434 patients found that CPAP lowered systolic pressure by about 2.6 mmHg in people whose blood pressure was uncontrolled at the start, and not at all in those whose pressure was already controlled.6
What gets checked
- Symptoms. Loud snoring, pauses in breathing noticed by a partner, waking unrefreshed and daytime sleepiness are the usual clues.
- A sleep study. Diagnosis requires overnight measurement of breathing, at home or in a sleep lab.
- Blood pressure, including readings that stay high despite treatment. This is one of the situations where guidelines advise looking for sleep apnea.
- Heart rhythm. Atrial fibrillation that keeps returning is another.
- The standard risk factors. Cholesterol, blood sugar and waist size are assessed as they would be for anyone.
Decisions about treating sleep apnea belong with a sleep clinician. Symptoms, safety and quality of life are established reasons to treat, whatever the effect on heart events turns out to be.
Your next step
If you snore heavily, wake unrefreshed or have blood pressure that is hard to control, tell your doctor and ask whether a sleep study makes sense. For the wider picture on rest and the heart, see our guide to sleep and heart disease, and for how risk is measured overall, our guide to a heart disease risk assessment.
You can also answer the three quick questions in the screener on the Cardio Res-Q program page. Poor sleep is among the risk factors listed on that page. If you want to know whether sleep testing can be arranged, ask our team.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Does CPAP prevent heart attacks and strokes?
Randomized trials have not shown that it does. In the largest trial, people with sleep apnea and existing cardiovascular disease had similar rates of events with or without CPAP over nearly four years. CPAP did improve sleepiness, snoring, mood and quality of life, which are valid reasons to use it.
Can sleep apnea cause high blood pressure?
The evidence points that way. In a study that measured sleep breathing and then followed people for four years, the odds of developing high blood pressure rose in step with the severity of apnea, independent of weight and other factors. CPAP lowers blood pressure modestly in people whose pressure is not controlled.
I do not feel sleepy during the day. Could I still have sleep apnea?
Yes. Most participants in the largest CPAP trial had moderate-to-severe sleep apnea with minimal sleepiness. Snoring, witnessed pauses in breathing and blood pressure that resists treatment are reasons to ask about testing even if you feel alert.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
