Sleep is a biological necessity, of the brain and by the brain and for the brain. Interrupting sleep for any reason increases pain and has a significant impact upon mood and memory.
Only a small number of things go wrong with sleep, luckily this makes sleep clinics relatively simple. Working within the largest sleep service in the North of England; we will see the sleepy (hypersomnia), the sleepless (insomnia), those with broken clocks (circadian rhythm disorders) and things that go bump in the night (restless legs and parasomnia – for example sleepwalking).
Most of our referrals are those with hypersomnia; people who are too sleepy to get through the day without napping, often with family and work complaining. It often surprises me how long they take to get to our clinic. Going to the GP with “tired all the time” almost always prompts a hunt for daytime conditions such as anaemia, thyroid disease or screening for depression. Finally, the penny drops and questions about falling asleep in the day are asked.
All of the primary sleep disorders remain underdiagnosed and maybe none more so than obstructive sleep apnoea. This is loud snoring worsening over months and years, eventually causing the airway to collapse with complete cessation of breathing (apnoea). Oxygen levels drop and the oxygen desaturation causes a brief awakening that restarts breathing. However, the patient is rarely aware of this during the night. Opioids influence many aspects of breathing – they reduce respiratory rate, tidal volume, reflex responses to hypercapnia and hypoxia but arguably the most important effect is likely to be relaxation of the upper airway dilator muscles to cause or worsen existing obstructive sleep apnoea.
Nobody expects obstructive sleep apnoea, doctors and patients expect sleep apnoea about as much as they expect the Spanish Inquisition, possibly less*. This is a disease that affects 10% of all men and 5% of all women of all shapes and sizes over the age of 40. A recent study by the British Lung Foundation in 2014 compared the known population prevalence rates to the diagnosis rates and suggested that 80% of cases remain undiagnosed.
By the time we factor in the recognised risk factors of obesity (in particular neck circumference >17 inches), age, and drugs on prescription that are muscle relaxants (alcohol, benzodiazepines, opioids) then sleep apnoea is a condition that must be remarkably frequent in those with chronic pain on high doses of opioids. It is indeed very common. Every study that has screened for sleep apnoea within pain clinics or screened patients on regular opioids has found moderate or severe sleep apnoea in 30-50% of those studied. Those on higher doses of opioids or with higher BMI had higher rates. The figure is worth repeating – up to half of the pain clinic will stop breathing thirty, forty, fifty times an hour, every hour, every night. Patients will wake with a sandpaper dry throat, unrefreshed from the night with a sleepy day. However many hours they spend in bed, they cannot stay awake – the simplest screen for daytime sleepiness is the Epworth Sleepiness Score typically showing a score well above the normal range of 10.
Once people arrive at the clinic, most of our patients will have a simple domiciliary sleep study in their own bed at home. They return the equipment the next day and if they have moderate or severe sleep apnoea we treat them with continuous positive airway pressure (CPAP). This is a cost effective and often life transforming therapy. For obstructive sleep apnoea, when the airway is splinted open, then uninterrupted sleep returns. The effect on mood, daytime alertness, hypertension and well being is clear. Screening protocols have now been developed within our local pain clinic and they routinely refer many for assessment and then treatment. It often helps patients to understand the link between opiates and the side effects they cause.
One standard, but occasionally challenging part of the sleep clinic assessment is asking about driving and driving safety. Those with sleepiness from untreated obstructive sleep apnoea are at higher risk of crash, an estimated 5-7 times that of the background population and the condition is notifiable to the DVLA. Once treated, patients can quickly restart driving. Driving simulator data from the UK showed that 24% of those with severe sleep apnoea failed a simulator test. Therefore, we routinely ask all of our patients if they have had near misses, claims on insurance or crashes in the last year. It is a really simple set of questions to build into a history, you may be surprised how many say yes. Many are aware they are at risk, are relieved to have treatment and may have already reduced driving distance or stopped entirely after a near miss. Others deny any problem at the wheel despite scoring highly on the Epworth Sleepiness Score and being asleep in the waiting room! Being stopped from driving has a significant impact on day to day life and independence. We have spent many hours within our service discussing the best and most tactful ways to approach the discussion. Fast tracking professional drivers through the service and clear discussions about how quickly they will be able to restart helps (a bit). It does often motivate patients to start and then to continue CPAP. Most of our patients want to drive and want to be safe behind the wheel.
The central sleep apnoea that can come with high dose opioids can be more of a challenge. My referrals coming from the pain clinic may well be patients who have already stopped driving and rarely leave the house. We have patients who have done all we ask, worked hard to use their CPAP machine and their automatically recorded compliance data is high. But they remain sleepy, the cause remains their medication. The discussion may have to be that before we can recommend restarting driving, they need support to reduce and stop their medication. We discuss and explain the pauses in breathing that happen at night, we often show patients their own overnight data and the effect on increasing their blood pressure. It can help to link feeling worse on opioids than off them.
For those with dependence upon opioid medication, reduction and cessation can of course be hard and we must understand the drivers for change for each patient we see. How do we motivate people to do something initially uncomfortable for long term well being? One driver for change may be driving.
Dr Kirstie Anderson, Regional Sleep Service, Newcastle.
*Cultural reference that can of course be amended for those under the age of forty. No-one expects a game show host to become President...
Rose AR et al. J Clin Sleep Med. 2014
www.blf.org.uk/support-for-you/osa This contains the Epworth Sleepiness Score and a clear self help guide for patients.