Why Do Some People Have Daytime Sleepiness Even on CPAP Therapy?

A common symptom of sleep apnea is daytime sleepiness. In fact, it may be this sleepiness that is the first reason why a person sees their doctor. Once sleep apnea is diagnosed, many with the condition will use a CPAP (continuous positive airway pressure) machine at night. For the majority of people with sleep apnea, using CPAP will help their symptoms.¹

However, about 10 percent of people on CPAP will still have excessive daytime sleepiness (EDS). This residual or resistant EDS can be a serious problem. It may lead to fatigue, difficulty functioning at work, falling asleep at inappropriate times (like while driving), and more. Residual EDS is typically defined as sleepiness that impairs functioning despite CPAP therapy. It usually also requires a high score on symptom scales like the Epworth Sleepiness Scale.¹

Who gets excessive daytime sleepiness on CPAP?

Anyone can have residual EDS after CPAP treatment. However, some studies have suggested that people at a higher risk are generally younger (less than 55 years old) and have lower mood, quality of life, and worse outlook on their overall health.^1,2

Some have also suggested that the rate of daytime sleepiness before treatment is greater in those with residual EDS than those without it. Often, people with residual EDS have another underlying condition that impacts sleep, such as depression or obesity.^1,2

First steps to take

When evaluating residual EDS, a doctor will consider several different things. First, they will need to take a thorough look at easily changeable or explainable causes.

An example of an easily adjustable cause of EDS is CPAP misuse or malfunction. If a person is not regularly using their CPAP or not using it correctly, their sleep may be impaired. Air leaks, masks not fitting properly, fear of CPAP treatment, and device settings will be investigated. Sometimes, it may be necessary for a person to complete another sleep study (polysomnography) with their CPAP machine to determine if their device settings are right for them.^1-4

Considering other possible factors for EDS

If there are no issues with the CPAP device or how often it is used, your doctor will consider other medical conditions that can cause daytime sleepiness. Some of these include:^1-5

• Thyroid conditions
• Kidney issues
• Depression, anxiety, other psychological conditions
• Parkinson’s disease
• Alzheimer’s disease
• Multiple sclerosis

For example, obesity and COPD may cause a person to hold onto too much carbon dioxide due to poor breathing. This can then lead to daytime sleepiness, which may worsen if a person already has sleep apnea. It also may be possible for a person to have a co-occurring sleep disorder like narcolepsy alongside their sleep apnea. Certain drugs can also cause sleepiness and will be considered as well.^1-5

Another common cause may be related to sleep behaviors or poor sleep hygiene. In the general population, daytime sleepiness can be quite common due to inadequate sleep duration or environment. Keeping a sleep log may reveal less sleep than expected each night, regardless of CPAP therapy. Further, environmental factors like lighting, television use, inconsistent routines, and caffeine intake may also impact good sleep and contribute to daytime sleepiness.^1-5

Why does residual EDS occur?

As mentioned, residual EDS can occur due to issues with the CPAP machine and its use, or it may be related to other underlying medical issues. However, in many cases, a clear, underlying cause may not be found.

Experts have suggested many possible reasons why residual EDS may occur. Some have thought that periods of hypoxia (low oxygen, like in sleep apnea) may cause damage to areas of the brain controlling the sleep-wake cycle. Others suggest that hormonal balance, gut bacteria, or faulty activation of the fight-or-flight stress system may be involved. Many believe that chronic inflammation or individual changes in the structure of a person’s sleep cycle may play a role. However, more research is needed to understand the factors at work in residual EDS without a known cause.^1,2,4,5

Medical treatment of residual EDS

Ensuring proper CPAP use and settings, targeting other comorbid conditions, and lifestyle changes (like good sleep hygiene) are first-line options for treating EDS. However, if EDS is persistent despite all of these and an underlying cause cannot be found, there are some drugs that can be used. Some of these include:^1-5

• Provigil (modafinil) and Nuvigil® (armodafinil) – Both of these drugs work on the neurotransmitter dopamine, which plays a role in many bodily functions. The exact way they work in the body is unknown.
• Sunosi (solriamfetol) – Impacts dopamine and norepinephrine balance in the body
• Wakix® (pitolisant) – Impacts the regulation of histamine in the body
• Amphetamines or methylphenidate: Stimulants that are not as commonly used as other options

If the cause of a person’s EDS despite CPAP therapy is unknown, these drugs may be helpful. A doctor or healthcare provider can help determine which ones, if any, might be most useful.