CPAP · Persistent fatigue · Second opinion

Tired Despite CPAP?

Written by Dr Ari Manuel, Consultant in Sleep & Respiratory Medicine · Last reviewed October 2026

You were told your CPAP is working, or you have worn it faithfully for months or years, and yet you still feel exhausted. It is a frustrating position, and a common one. Persistent tiredness on CPAP does not necessarily mean the treatment has failed, but it does deserve a proper look.

Why some people stay tired on CPAP

CPAP treats obstructive sleep apnoea by keeping the airway open, but sleepiness and fatigue can have more than one cause. Treatment can be partly effective, or the tiredness may be coming from something else altogether. A careful review looks at both.

Common causes

• Mask leak or poor fit. Air escaping around the mask can fragment sleep and reduce the effectiveness of treatment, even if you are unaware of it.
• Pressure settings. Pressure that is too low may not control the airway; pressure that is too high can cause discomfort, arousals or air swallowing.
• Residual apnoea. Some people continue to have breathing events on treatment. Device data can show this, and it is not always visible from the usual summary figures.
• Other sleep disorders. Insomnia, restless legs, periodic limb movements, circadian rhythm disorders and central hypersomnias can all exist alongside sleep apnoea.
• Non-sleep causes. Low iron or thyroid levels, low mood, medication effects, pain, hormonal factors and other medical conditions are frequent contributors to fatigue.

Why a proper review matters

It is tempting to conclude that CPAP does not work for you and give up on it, or to assume that tiredness is simply something to live with. Neither is necessarily true. A structured review of your device data, mask and symptoms, together with a full clinical history, can often identify what needs to change. Sometimes the answer is a simple adjustment; sometimes it is a different type of ventilatory support or investigation for another condition. Results vary, and a review cannot guarantee that symptoms will resolve.

Persistent fatigue, memory and concentration

Ongoing tiredness often brings difficulties with memory, attention and mental clarity. People describe losing their train of thought, struggling to concentrate at work or forgetting appointments. These symptoms are common in sleep-disordered breathing and are a frequent reason for seeking help. They can also have other causes, which is another reason to investigate them properly rather than assume.

Research has also linked long-term, untreated or inadequately treated sleep apnoea with an increased risk of cognitive decline and conditions such as dementia. This evidence comes largely from observational studies, which show an association rather than proving cause and effect, and most people with sleep apnoea will not develop dementia. It does, however, support the value of making sure sleep apnoea is properly diagnosed and effectively treated, and of not leaving persistent symptoms unexplained.

What a second opinion consultation offers

A second opinion consultation gives you time with a consultant to go through your diagnosis, sleep study results, CPAP download data and symptoms in detail, and to consider whether further tests such as a repeat or extended sleep study would be useful. You receive a written letter setting out the findings and recommendations. Remote consultations are available throughout the UK, with face-to-face appointments at Nuffield Hereford and Nuffield Cheltenham.