An article getting some press is in the January edition of the Sleep Journal. In it, the authors discuss how people use the terms sleepiness and fatigue as if they were the same thing - but they are not. In patients with obstructive sleep apnea (OSA), patients sometimes complain more of fatigue, tiredness, and lack of energy rather than sleepiness. CPAP has been shown to reduce subjective (patient-perceived) and objective (measurable) sleepiness, but has not been shown conclusively to reduce fatigue.
The authors investigated the levels of fatigue, energy/vigor, and sleepiness before and after a three week trial of CPAP in OSA patients. They compared using therapeutic CPAP to fake (sham) CPAP. A total of 59 patients were studied.
The results showed that therapeutic CPAP significantly reduced fatigue and sleepiness, and increased energy/vigor levels compared to sham CPAP. Of note, CPAP was only able to reduce sleepiness in those patients who had a high degree of sleepiness before CPAP. This makes sense and is consistent with what I see in my practice. The authors theorize that fatigue might improve with CPAP because it reduces inflammation that can be seen in untreated OSA.
One reason this study is important is because of the effects on fatigue and energy/vigor levels. This is a common complaint in patients with OSA and is not measured regularly by us sleep physicians. Perhaps it is time we did include a fatigue measure the same way we always ask about sleepiness.