Sleep apnea and weight-loss surgery: why testing and CPAP matter

Loud snoring, waking up tired, dozing off in the afternoon. Many people put these down to a busy life. Before weight-loss surgery, they are worth a closer look, because they can be signs of obstructive sleep apnea.

What is sleep apnea?

In obstructive sleep apnea, the airway in your throat narrows or closes again and again while you sleep. Breathing becomes very shallow or stops for a few seconds, oxygen levels drop, and your brain wakes you briefly so you breathe again. Most people do not remember these wake-ups. Extra fat in and around the neck is one of the main reasons the airway collapses.

Over time, untreated sleep apnea is linked with high blood pressure, heart disease, heart rhythm problems, stroke, type 2 diabetes and car crashes caused by drowsiness.

How common is it?

Very common in people preparing for bariatric surgery. Depending on the study, between about 35% and 94% of people having this surgery have sleep apnea. Many do not know it: Canadian guidelines note that up to half of people with significant sleep apnea before bariatric surgery have never been diagnosed. Sleep apnea is more common in men, and it does not always match BMI. Some people with a lower BMI have severe sleep apnea.

Why it matters for surgery

Anesthesia, sedatives and strong pain medicines relax the muscles of the throat and can slow breathing. In someone with sleep apnea, this can make breathing harder in the hours after surgery. Canadian guidelines note that people with sleep apnea may have more complications and longer hospital stays after bariatric surgery, and that placing the breathing tube can be harder.

That is why guidelines suggest screening everyone for sleep apnea before bariatric surgery, and treating it when it is found.

Testing before surgery

Screening often starts with a short questionnaire. One widely used tool, called STOP-Bang, has eight yes-or-no questions about:

• Loud snoring, daytime tiredness, and whether anyone has seen you stop breathing in your sleep.
• High blood pressure.
• Your BMI, age, neck size and sex.

A higher score means a higher chance of moderate or severe sleep apnea. Questionnaires can miss it in people living with obesity, though, so Canadian guidelines advise a low threshold for a sleep study. A sleep study records your breathing and oxygen levels overnight. It shows whether you have sleep apnea and how severe it is.

Why CPAP matters

CPAP (continuous positive airway pressure) is a small machine that gently blows air through a mask while you sleep. The air keeps your airway open. An international expert guideline on sleep apnea and bariatric surgery recommends CPAP for everyone with moderate or severe sleep apnea, and continuous oxygen monitoring in the first period after surgery. It also advises keeping sedatives and strong pain medicines to a minimum.

• If you are prescribed CPAP, use it every night before surgery, so you get used to it.
• Bring your CPAP machine and mask on the day of surgery.
• Tell your team about any sleep apnea diagnosis, even if you stopped using your CPAP.

After surgery

For many people, sleep apnea improves as weight comes down. A review of 69 studies with about 13,900 people found that more than 75% had at least some improvement in their sleep apnea after bariatric surgery.

It does not always go away, though. Canadian guidelines note that moderate to severe sleep apnea can still be present a year after surgery, and that it can come back later, even without weight regain. So do not stop CPAP on your own. As your weight changes, your mask may need refitting and your pressure setting may need adjusting. Your doctor can tell you when a new sleep study makes sense.