The guide

When does a low night mean a sleep study?

By GyroscopeUpdated November 14, 202614 sources

Ask about a sleep study when the low points keep coming night after night, when someone has seen you stop breathing in your sleep, or when you snore loudly and you’re sleepy in the day. A watch can point you toward a test. Only a sleep study can tell you whether you have sleep apnea.

One low night isn’t on that list. Healthy sleepers’ lowest point averaged about 90 in a sleep lab, and one evening of drinks can lower the next night too.

Why does one low night make people think of sleep apnea?

Because it’s the condition everyone has heard of, and a watch now hands you a number for it every morning. A dip to 87 at 3 am looks like proof. Some watches also send a sleep apnea notification, which makes any low number feel like part of the same story.

But a healthy night dips too. In 350 people whose sleep studies came back normal, the lowest point of the night averaged 90.4, and plenty went lower. What separates sleep apnea from a normal night is repetition, the same thing happening again and again through the night and night after night.

What happens in sleep apnea?

In sleep apnea, breathing stops and restarts many times while you sleep, NHLBI explains, which can keep your body from getting enough oxygen. In the common type, obstructive sleep apnea, the upper airway gets blocked over and over and the airflow drops or stops. In the rarer central type, the brain doesn’t send the signals to breathe.

Snoring comes from the same place. MedlinePlus says the sound is made by tissues at the top of the airway that strike each other and vibrate when airflow is partly blocked. Snoring alone is common. Snoring with pauses, gasps and daytime sleepiness is what doctors want to hear about.

On a watch, apnea can show up as a train of dips through the night instead of one gentle slope. In the 1996 sleep lab study, people with obstructive sleep apnea ran lower than healthy sleepers.

A simple way to picture it

Picture breathing through a soft, floppy straw. Most of the time air gets through. When the straw sags a little, it rattles, which is snoring. When it folds shut, the air stops until you gasp and it pops open again. A night with that happening many times an hour leaves you tired however long you were in bed.

How common is it?

It’s more common than most people think. Using the long-running Wisconsin Sleep Cohort and US body weights from 2007 to 2010, researchers estimated how many US adults have moderate to severe sleep-disordered breathing, meaning 15 or more breathing events an hour.

Those rates were 14% to 55% higher than in the early 1990s, depending on the group, as body weights rose.

What signs do doctors ask about?

A common checklist doctors use has eight yes or no questions, known as STOP-Bang.

• Do you snore loudly?
• Do you often feel tired or sleepy in the day?
• Has anyone seen you stop breathing in your sleep?
• Do you have high blood pressure, or take medicine for it?
• Is your BMI over 35?
• Are you over 50?
• Is your neck large?
• Are you male?

In studies of the checklist, the more yes answers people had, the likelier a sleep study was to find moderate to severe apnea, from about 18% with two or fewer up to 60% with seven or eight. NHLBI adds gasping for air, and notes that loud snoring is more common in men while tiredness, headaches and insomnia are more common in women.

High blood pressure is on the list for a reason. bloodpressure.guide’s morning answer covers how untreated sleep apnea can push morning numbers up.

What can a watch tell you?

A watch or ring can show a pattern of low nights, and some watches look for breathing trouble directly. Apple’s sleep apnea notifications use the watch’s motion sensor to look for breathing disturbances, need at least 10 nights of wear over 30 days, and are meant for people 18 and older who haven’t been diagnosed. They run on Series 9 or later, Ultra 2 or later and SE 3. Apple says the feature is “not intended to diagnose” sleep apnea, and suggests talking to your doctor and exporting a PDF report from the Health app.

What a watch can’t do is tell you that you have sleep apnea, or that you don’t. Its oxygen numbers come from light shone through skin, and they can show too high on darker skin. In hospital patients whose finger oximeter showed 92 to 96, true oxygen was under 88 for 11.7% of Black patients’ measurements and 3.6% of White patients’. A normal-looking night with loud snoring and pauses still deserves a doctor’s ear.

What is a sleep study?

It’s a night of measured sleep that counts how often your breathing stops or gets shallow, and what that does to your oxygen. NHLBI says a sleep study can show which type of sleep apnea you have and how serious it is.

There are two kinds. The 2017 guideline from the American Academy of Sleep Medicine says a home sleep apnea test is fine for adults with no complicating conditions whose signs point to moderate to severe apnea. People with significant heart or lung disease, possible muscle weakness affecting breathing, chronic opioid use, a past stroke or severe insomnia should have a full study in a sleep lab. If a home test comes back negative or unclear, the next step is a lab study.

The three-night check makes a dated card of your numbers, drinks, sleeping position, snoring and sleepiness, which is the kind of thing your doctor will ask about.

What helps?

NHLBI lists the treatments.

• A breathing machine. Positive airway pressure (CPAP and its cousins) is the most common treatment.
• Sleeping on your side. In 12,036 sleep-center patients with apnea, two in three had more breathing events on their back, and 28% had them only on their back.
• Less alcohol, especially before bed. In people with diagnosed sleep apnea, alcohol added about 7 breathing events an hour across trials.
• Weight loss. In the SURMOUNT-OSA trial, adults with obesity and moderate to severe apnea who took tirzepatide for a year had about 25 fewer breathing events an hour, against about 5 on placebo. NHLBI notes the FDA has approved a weight-loss injection for moderate to severe sleep apnea with obesity. bodyfat.guide’s tirzepatide page covers the drug.
• Mouth devices. Custom mouthpieces from a dentist, for people who can’t use a machine.
• Surgery. Including an implanted nerve stimulator, tonsil removal and jaw surgery, when other treatments don’t work.

Treating it does more than fix the numbers. NHLBI says untreated sleep apnea raises the risk of stroke and heart attack, and can cause trouble with concentrating, deciding and remembering.