Should Mild Sleep Apnea Be Treated?
In this article, I will unpack the scientific evidence informing both sides of the debate about how mild sleep apnea should be managed. To start, let's clarify some key concepts.
What Is Mild Sleep Apnea?
In adult patients (≥ 18 years of age), mild sleep apnea is defined as a home sleep apnea test showing an apnea hypopnea index (AHI) between 5 and 15. AHI is synonymous with RDI (respiratory disturbance index) or REI (respiratory event index - more commonly used on a home sleep study report). In plain English, this means that the sleep study showed that you had an average of 5 to 15 abnormal breathing events per hour.
An obstructive apnea refers to an abnormal breathing event characterized by complete collapse of the upper airway for at least ten seconds. A bystander witnessing the event would not hear you breathing but would see your chest and abdomen rising and falling in an attempt to breathe.
A hypopnea is defined as a partial collapse of the upper airway for at least ten seconds that causes a ≥3% blood oxygen drop (oxygen desaturation is the correct medical terminology). A bystander could not detect a hypopnea just by observing you - sleep test equipment is required. Incidentally, Medicare, going against the AASM's criteria, nonsensically requires a 4% oxygen desaturation to define a hypopnea.
In the aggregate, hypopneas are much more common than obstructive apneas. Importantly, apneas and hyopneas have the same negative physiological effects on your body. Patients often tell me that they have "hypopnea syndrome" because the majority of abnormal breathing events on their sleep apnea studies were hypopneas. This is a common misconception as there is no such thing as hypopnea syndrome. Your AHI could be comprised entirely of hypopneas and, if it's ≥5, you meet criteria for the diagnosis of obstructive sleep apnea.
What's the Controversy about Treating Mild Sleep Apnea?
There is a lot of evidence to support the lack of a direct link between AHI and daytime sleepiness levels. This means that there are cases of sleep apnea where the person has an AHI of 5 and is barely able to keep her eyes open, but someone else might have an AHI of 100 and he reports zero daytime sleepiness. Therefore, if you have an AHI ≥5 and excessive daytime sleepiness (or EDS, also known as hypersomnolence or hypersomnia), most sleep experts would recommend treating the sleep apnea.
However, there is disagreement in the sleep medicine community about what to do when sleepiness is not an issue and the AHI is between 5-15. The current debate centers around studies that have looked at outcomes from treating mild sleep apnea and found mixed results. Let's delve into the background framing the discussion.
Running the Option - The 2009 Guidelines
In 2009, the American Academy of Sleep Medicine (the field's governing body) published the Clinical Guideline for the Evaluation, Management and Long-term care of Obstructive Sleep Apnea in Adults. In this thirteen-page manifesto, continuous positive airway pressure (CPAP) was recommended for moderate to severe OSA as a "guideline," i.e. having the highest level of evidence to support the recommendation. However, CPAP was only given an "option" recommendation for mild sleep apnea, due to the less compelling medical evidence at that time to support its use in this population.
The treatment algorithm described in the guideline suggests that patients with "symptoms" and mild sleep apnea should be treated with CPAP. What constitutes symptoms? This guideline includes the following list:
- unintentional sleep episodes during wakefulness
- daytime sleepiness (usually assessed with the Epworth Sleepiness Scale)
- unrefreshing sleep
- waking up breath-holding, gasping, or choking
- bed partner describes loud snoring, breathing interruptions, or both
Although not explicitly stated, this guideline implies that if you're asymptomatic and have mild sleep apnea, you don't really need to use CPAP. The faction in the sleep community that is against treating mild sleep apnea is represented by Dr. Michael Littner's editorial Mild Obstructive Sleep Apnea Should Not Be Treated. Dr. Littner highlights the lack of scientific evidence to support benefit in health or quality of life outcomes in mild sleep apnea patients treated with CPAP. He also points out that one study showed that patients with relatively low AHIs are unlikely to stick with CPAP use long-term. Interestingly, another perspective on the data is that it is quite logical that the subjects in this study didn't benefit from CPAP because they didn't use it enough.
The "pro-CPAP" camp cites the Sleep Heart Health Study's key findings of an AHI >5 being associated with an increased risk for:
- worse EDS and quality of life
- increased risk of hypertension and cardiovascular disease (heart attack, heart failure, stroke)
Just when You Learn the Rules, the Game Changes
In 2014, the AASM published its updated third edition of the International Classification of Sleep Disorders, the field's diagnostic bible. Based on new research and expert opinion, the diagnostic criteria for obstructive sleep apnea were expanded to also include an AHI ≥5 and the following medical co-morbidities, irrespective of symptoms:
- mood disorders
- cognitive dysfunction
- coronary artery disease
- congestive heart failure
- atrial fibrillation
- type 2 diabetes mellitus
Therefore, the indication to treat those with mild sleep apnea expanded to include both "symptomatic" patients as previously described, and those with the above medical problems. This vastly increased the number of patients with mild sleep apnea requiring treatment.
More Than One Way to Skin This Cat
Compared to more advanced degrees of sleep apnea, a diagnosis of mild sleep apnea opens up a world of treatment possibilities. The CPAP machine (and its more versatile cousin, the APAP machine) is still considered the "gold standard treatment" for mild sleep apnea. However, patients may also be candidates for an oral appliance for sleep apnea, nasal EPAP, positional therapy, exciteOSA, or lifestyle interventions, depending on their situations.
Oral appliances push the mandible out, helping prevent the tongue from falling back and obstructing the airway. Research seems to show that relatively thin patients with small or recessed jaws tend to do particularly well with this type of treatment.
exciteOSA is a new treatment for primary snoring and mild OSA with a completely different mechanism from existing therapies. Regular use of this device can "tone" your tongue muscle so it is less likely to fall back and block your airway during sleep. This device is FDA approved for primary snoring and mild obstructive sleep apnea only.
If your AHI is only ≥5 when you're on your back, positional therapy might work for you. There are various devices in the positional therapy armamentarium that are designed to prevent you from moving onto your back while sleeping. In terms of lifestyle modification, if you're overweight or obese than weight loss is probably the number one thing that you can do. In addition, quitting smoking, and refraining from alcohol and sedative and hypnotic medications near bedtime can improve AHI significantly in some patients.
Whichever treatment you choose, it is important to have a follow-up apnea sleep study to verify that your AHI is now <5 and oxygen saturation is (ideally) >90% for your entire sleep period.
The Bottom Line
As a clinician, I've learned that there's a fatal flaw in the current paradigm for only treating mild sleep apnea in patients that report symptoms or have an associated medical disorder. Sometimes further investigation reveals that supposedly "asymptomatic" patients have symptoms hiding in plain sight - you just have to ask the right questions.
Many mild sleep apnea patients have told me over the years that they feel fine both when they wake up and during the day. Many of these patients register a normal score on the Epworth. But occasionally when I dig deeper and ask more specific questions like, "How long can you read?" the answer is, "Oh, I don't read because I'd fall asleep immediately." Another typical scenario is that patients will enter a zero in the "likelihood of dozing as a passenger in a car" field on the Epworth - indicating no sleepiness in this situation. When I dig deeper, patients sometimes tell me, "I'm never a passenger - I always drive because if I was a passenger I'd doze off for sure."
Essentially, patients sometimes devise countermeasures by restructuring their lives to avoid situations in which they are likely to get sleepy. Other patients whom I have encountered have habituated to their daytime symptoms and aren't aware of how good they could feel with treatment.
If you've been diagnosed with mild sleep apnea and are on the fence as to whether to start treatment, I'd suggest discussing the situation with an experienced sleep medicine physician. I often suggest that patients try treatment for about a month to see how they respond, and then reconvene with me to discuss and make a final plan.
Final Thoughts on CPAP vs Alternatives in Mild Sleep Apnea
If you do have one of the medical co-morbidities discussed earlier in this article, I recommend CPAP over alternative treatments. Without question, CPAP has the most robust medical literature supporting its benefit in preventing the progression of sleep apnea's health consequences.
If you have an aversion to CPAP and you're healthy, I'm more open-minded to trying CPAP alternatives. I always counsel my patients that alternatives will usually not work quite as well as CPAP and they may have some residual snoring. The way I like to frame the decision is to expect alternatives to be typically about 85-90% as effective as CPAP. Nevertheless, using something 100% of the time that is 85%-90% effective is infinitely better than 0% usage of the 100% effective CPAP machine that is collecting dust in your closet.
Joseph Krainin, M.D., FAASM is the founder of Singular Sleep, the world's first online sleep center. He is a Fellow of the American Academy of Sleep Medicine and board-certified in both sleep medicine and neurology. He has been practicing medicine for over 10 years.