Many use the terms sleepiness and fatigue interchangeably. Although these physical complaints are both similar, they are distinct in that fatigue is often described as feeling a lack of energy and sleepiness is described as the propensity to actually fall asleep. Both complaints may have physically distinct mechanisms and severity of these complaints can even be gauged with separate questionnaires. So since we know treating sleep apnea with CPAP can alleviate sleepiness, can it also alleviate fatigue?
In order to answer this question, a group of researchers examined 59 subjects who had previously been diagnosed with OSA but who were untreated. This population also had complaints of sleepiness and fatigue. Questionnaires were administered that assessed fatigue and vigor, which is defined as enthusiasm or intensity. Standard questionnaires assessing sleepiness were also administered. All subjects were then prescribed to sleep apnea treatment (CPAP), but only half of these subjects had working treatment. The non-working half of machines looked and sounded like real CPAPs, but they provided no pressure. Because of this, they are used to test for placebo effects. Questionnaires were again administered after treatment began.
After 3 weeks of CPAP treatment (or fake CPAP), both groups were compared. Their sleepiness and fatigue scores before and after treatment were tabulated, and results showed the treated group had a decrease in fatigue and an increase in vigor. Those with the most fatigue at treatment onset showed the greatest improvement. In addition, those with the most sleepiness at treatment onset showed the greatest improvement in sleepiness1.
So what did we learn here? First and foremost, most of us learned that fatigue and sleepiness are two different entities. Next, since fatigue seems to exist separately from sleepiness, it may take more a cup of coffee to fix it. For some people, CPAP may be the only way to alleviate fatigue, creating yet another reason to start PAP treatment and to stick with it.
References:1. Lee MH, Lee SA, Lee GH, Ryu HS, Chung S, Chung YS, Kim WS. Gender differences in the effect of comorbid insomnia symptom on depression, anxiety, fatigue, and daytime sleepiness in patients with obstructive sleep apnea. Sleep Breath. 2013 May 9.