Obstructive sleep apnea is the most common type of sleep apnea, and it’s best known for causing wakeful nights that result in daytime fatigue. But many people with sleep apnea are not aware that the disorder also poses a threat to their cardiovascular health.
Growing evidence shows that sleep apnea can increase the risk of high blood pressure, coronary artery disease, heart attack, stroke, and irregular heart rhythms such as atrial fibrillation (AFib).
While that’s distressing news, there is an upside. Evidence also suggests that treatment of sleep apnea with a nasal mask known as continuous positive airway pressure (CPAP) can help lower some of those risks. Yet most people with sleep apnea don’t even know they have the condition, so it usually goes undiagnosed and untreated.
How sleep apnea affects the heart
The link between sleep apnea and cardiovascular disease isn’t entirely understood.
People with sleep apnea repeatedly stop breathing during sleep because an airway becomes blocked. With each pause in breathing, the oxygen level in the blood drops. Frequent bouts of low oxygen levels during sleep may damage blood vessels and lead to irregular heart rhythms.
In addition, sleep is normally a time when the cardiovascular system rests and heart rate and blood pressure fall. But with sleep apnea, each episode of lowered oxygen triggers a response in which the heart beats faster and blood pressure rises.
Over time, that pattern may contribute to a range of cardiovascular diseases, especially when sleep apnea isn’t treated. For example, a 2015 study found that participants with untreated, severe sleep apnea were 2.6 times more likely to develop heart problems compared with participants who didn’t have sleep apnea.
However, when the researchers also included CPAP-treated subjects in their analysis, the association between sleep apnea and heart disease was weaker. The study, published in the journal Sleep, was based on data from 1,280 men and women whose health was tracked for up to 24 years in the ongoing Wisconsin Sleep Cohort Study.
Similar results were reported for stroke risk in a 2014 study published in the American Journal of Respiratory and Critical Care Medicine.
Researchers in Spain followed 967 women for an average of about seven years. They found that women with untreated, moderate-to-severe sleep apnea had a significantly increased risk of stroke compared with those who didn’t have sleep apnea. But women with CPAP-treated sleep apnea did not have a higher risk of stroke.
How CPAP treatment helps
CPAP, the most common treatment for sleep apnea, keeps the airway from closing during sleep, which prevents oxygen levels in the blood from falling and relieves stress on the heart. But additional studies are needed to know whether that translates into fewer heart attacks, strokes, and deaths.
Even so, treatment with CPAP has been shown to reduce a number of cardiovascular threats associated with sleep apnea.
Further, treatment may also reduce the frequency of recurrent episodes of cardiovascular problems as detailed below.
For instance, randomized controlled trials and meta-analyses have found that use of CPAP lowers blood pressure in many sleep apnea patients. Although the effect is modest, it is enough to decrease cardiovascular risk.
On the other hand, sleep apnea patients with uncontrolled or resistant hypertension—the kind that responds poorly to blood pressure medications—may have the most to gain from CPAP. Those patients were likely to experience a substantial reduction in blood pressure in a 2014 meta-analysis of 968 people with sleep apnea, published in the Journal of Clinical Sleep Medicine. The results held true even for patients with mild or moderate sleep apnea.
There is also evidence that treatment of sleep apnea can help control an irregular heartbeat. A 2015 meta-analysis, published in JACC Clinical Electrophysiology, evaluated data from seven trials with a total of 1,087 patients who had sleep apnea and AFib. All of the patients underwent treatment for their arrhythmia, but sleep apnea is a risk factor for recurrences of AFib even after such treatment.
However, the meta-analysis found that patients who used CPAP to manage their sleep apnea were 42 percent less likely to have a recurrence of AFib compared with those who didn’t use CPAP.
Stroke outcomes also improved with sleep apnea treatment in a 2015 study published in the Journal of Sleep Research. In the trial, 140 sleep apnea patients who suffered a first ischemic stroke were randomly assigned to receive conventional treatment for stroke plus CPAP, or conventional treatment only.
The CPAP group had a better neurological recovery and, at five-year follow-up, fewer cardiovascular events (such as a second stroke) and cardiovascular-related deaths, compared with the control group.
More benefits of treatment
There are many good reasons to treat sleep apnea. The benefits include greater alertness and less sleepiness during the day, as well as improved concentration and memory. Studies show that treating the disorder can also help lower blood pressure and may help control abnormal heartbeats and other cardiovascular consequences of sleep apnea. Here’s what you can do:
• Identify sleep apnea. Pay attention to signs, including complaints about snoring from a bed partner or family member, and excessive daytime sleepiness. If you suspect that you have sleep apnea, speak to your doctor. That’s especially important if you have cardiovascular disease.
• Use CPAP regularly. CPAP is often recommended for people with moderate-to-severe sleep apnea. If your doctor prescribes the device, try to use it every night.
In a 2016 study published in the Journal of the American Heart Association, 84 middle-aged adults with moderate-to-severe sleep apnea were treated with CPAP and followed for three months. The treatment improved their blood pressure, arterial stiffness (a sign of early atherosclerosis), and other measures of cardiovascular health. At that point, a subgroup of patients stopped using CPAP. Their improvements disappeared after one week.