Pain and Sleep: A Delicate Balance
Early in my career in pain management, I realized that there was a strong association between chronic pain and sleep. That realization inspired a journey of learning more about sleep. I joined the Academy of Sleep Medicine, which in turn led to attending scientific meetings and workshops and reading journals on sleep disorders. I also was the pain psychologist in the Oregon Health & Science University (OHSU) Pain Management Program, where I gained even more knowledge by working with the OHSU Sleep Program. A few years later, a large Portland-based chain of hospitals asked if I could assist in forming sleep centers in each of its facilities. This was a valuable experience, because I was able to work with some fine clinicians who specialized in pul-monology and sleep disorders. Based on these experiences, in addition to 35 years of clinical practice, I have some thoughts regarding pain and sleep that I would like to share with the readers of Practical Pain Management.
One of my primary messages for clinicians is to increase their awareness that sleep disorders should be given careful consideration when evaluating and treating the patient with chronic pain. The scope of this article is limited, so I encourage the reader to refer to the excellent book Sleep and Pain, published by the International Association for the Study of Pain (IASP), for a more in-depth treatment of the subject.1
Insomnia Poses Largest Challenge
The prevalence of chronic pain and the presence of a sleep disorder depend on a number of factors, including the type of pain, the age of the patient, gender, and the existence of comorbid conditions such as depression. My own clinical experience with adults confirms that a dual presentation of pain and sleep disorders occurs quite often, with an estimated incidence of 60% to 80%.2 The most prevalent primary diagnosis is insomnia, which is characterized by difficulty falling asleep and staying asleep. My own clinical experience also confirms that insomnia usually is present in a majority of patients with pain. Other sleep disorders, such as apnea and restless leg syndrome, also should be ruled out. But it is important to keep in mind that sleep diagnoses are not mutually exclusive.3
Primary insomnia is identified by two major factors: elevated psychophysiologic arousal and low sleep drive. Elevated psychophysiologic arousal should be considered as a continuum from low to high, with moderate to high levels of arousal usually diagnosed as some form of anxiety disorder. Further, the level of arousal can be situational, with variability depending on stress demands. In other cases, high levels of arousal can be static. This finding is less frequent, and if documented, serious psychopathology should be ruled out.
Psychophysiologic arousal is a key factor in both sleep and pain. But it has to be understood in the context of the various stages of sleep. In the normal sleeper, a painful stimulus triggers a clear reaction that occurs across all sleep stages—stages I/II (light to moderate sleep) and stages III/IV (deep sleep). In patients with chronic pain, this balance is disrupted: They typically experience a majority of stage I and II sleep, with little or no stage III/IV deep sleep. This disrupted sleep pattern has profound repercussions during waking hours, when the patient with pain often complains of daytime fatigue, depression, a loss of quality of life, and increased stress.
Another important consideration is the role of rapid eye movement (REM) and non–rapid eye movement (NREM) sleep. In normal sleepers, the NREM sleep cycle alternates between stages I and IV and then usually ends in a period of REM sleep. Because patients with pain often don’t achieve the deep stages of sleep, the transition to REM sleep often does not occur. Thus, in patients with chronic pain, treatment should be focused on restoring a balanced sleep cycle.
Since sleep is a natural state, one can argue that natural treatment options should be explored before pharmacologic options are used. The alternative approach—relying too heavily on sleep medications—can be highly problematic. In fact, I recently attended a large national pain meeting where there were a number of presentations describing the negative side effects of opioid therapy for chronic pain. The consensus was that constipation was the No. 1 negative side effect, with no mention of REM suppression! In my opinion, this is an important topic that often is overlooked in treating chronic pain; for a more detailed discussion, see chapter 5 in the IASP’s Sleep and Pain.4 The research findings summarized in the chapter state that the neurotransmitters acetylcholine, adenosine, and g-aminobutyric acid play a major role in the regulation of sleep and that these endogenous substances are all significantly altered by opioid therapy. Clinicians thus would be well advised to balance the benefits of long-term opioid therapy against its negative effects on sleep, including REM suppression. Patients also need to be educated about the ramifications of opioid-induced REM suppression. Further, patients on long-term opioid therapy, including intraspinal routes of administration, need to be carefully monitored for sleep disorders. And a sleep specialist should be part of a multidisciplinary treatment approach to chronic pain.
Don’t Place the Cart Before The Horse
Awareness of the interrelationship between pain and sleep is increasing. This is an encouraging development, because the need to include sleep evaluations within the context of multidisciplinary pain treatment often has been overlooked. It is hard to say whether pain or sleep disorders should be given primary consideration. Perhaps choosing one over the other is not the answer—regardless of the choice, it raises the possibility that we’d be putting the cart before the horse. What is important is the recognition that a very intricate relationship between pain and sleep exists on many levels. Neglecting either disorder in this delicate balance puts the patient—and clinician—at risk for treatment failure.