Introduction:
It is helpful to begin from the premise that pain is not an object; it is a type of event. Pain is a way of being-in-the-world. Bourke 2013
As Bourke stated above, pain is an experience typically dichotomized in the healthcare field as acute and chronic pain. This classification is based on a few factors, including the time-frame of pain chronicity, the presence of an identifiable mechanism of injury (MOI), or a distinct pathophysiological/pathoanatomical problem.
Before we get into this discussion, my bias is against dichotomizing the pain experience in this manner. With that said, most consider acute pain as pain whose onset is associated with a clear MOI or problem, and resolves within a timely manner somewhat arbitrarily related to tissue healing. There are layers of missteps in this logic, however this isn’t our focal discussion for the month so we will run with it.
For persistent (or “chronic”) pain, Treede 2015 defines it as,
...persistent or recurrent pain lasting longer than 3 months.
Pain as a word is rather complicated to define and we do not have sufficient time or space in this month’s review to do that discussion justice. With that said, there are a multitude of proposed definitions for the word pain throughout history, both scientifically and philosophically rooted. Inconsistencies in how to define pain, and for our context chronic pain, leaves a lot of unknowns and can cause heterogeneity in research data, leading many to search for a better definition and classification system. Steingrímsdóttir 2017
The International Association for the Study of Pain (IASP) proposed a new classification system for chronic pain in 2019, creating an additional dichotomy with chronic “primary” and chronic “secondary” pain. If you’ve helped those dealing with persistent headaches and migraines then you are likely familiar with such an approach, as the IASP pulled from the International Headache Classification to build this new system. According to the IASP,
The definition of the new diagnosis of CPP [chronic primary pain] is intended to be agnostic with regard to etiology; in particular, it aims to avoid the obsolete dichotomy of ‘physical’ vs ‘psychological,’ as well as exclusionary terms that define something by what is absent, such as ‘nonspecific.’ The meaning of ‘functional’ is also ambiguous. Some take it to mean ‘all in the mind’ and others as a ‘disorder of function.’ The introduction of ‘chronic primary pain’ eliminates this ambiguity. Nicholas 2019
The authors then outline criteria necessary to meet the diagnosis of chronic primary pain by having pain in one or more locations that:
Persists or recurs for > 3 months
Is associated with emotional distress (examples: anxiety, anger frustration, or depressed mood) and/or functional disability (ADLs affected as well as societal roles)
Cannot be better explained by another diagnosis (enter secondary classification) Nicholas 2019
The IASP’s journal, PAIN, previous January 2019 edition then has additional articles to review regarding the secondary classifications (chronic secondary pain syndromes): chronic cancer pain, chronic postsurgical or posttraumatic pain, chronic neuropathic pain, chronic secondary headache or orofacial pain, chronic secondary visceral pain, and chronic secondary musculoskeletal pain.
I have several concerns regarding these proposals. The bulk of these concerns lie with the meaningfulness of these labels for the patient, but extend to the championing of a biopsychosocial lens despite obvious physical/“body" labels tied to finding problems to explain pain. We are still left wondering whether something is a problem in the context of the patient’s pain experience through further bodily objectification.
Perhaps more importantly, who gets to be the arbiter of what is a “pain driver”? If history is a teacher in this regard, then we know consensus is VERY difficult to come by related to singular causes and functions of pain. Such an approach likely moves us no closer to helping the human in front of us with their pain-related suffering beyond providing a label that some are in search of. However, this label can be a double-edged sword, leaving a feeling of helplessness with a label that describes no identifiable problem(s) to fix and, in some cases, an unspoken approach of “just live with it [pain].” Although acceptance is often a necessary part of helping those dealing with persistent pain, we must ensure the “just live with it” narrative isn’t overtly or covertly disseminated, and instead we should focus on instilling self-efficacy in patients to gain some level of control over their situation and take steps towards their valued life goals.
Why is this being brought up when this month’s edition is all about sleep? As clinicians helping those dealing with pain-related suffering, we are tasked with examining influential variables that may help our patients gain control over, and influence or modulate their pain experience. The question we are here to answer with this month's review is whether sleep has a demonstrable relationship with persistent pain, and if so, what can we do about it.
For clarity, we will examine a recent review by Husak et al, Chronic Pain and Sleep Disturbances: A Pragmatic Review of Their Relationships, Comorbidities, and Treatments.
Sleep connection to persistent pain:
Persistent pain has an estimated prevalence rate between 17-25% in the general population, and 24-32% of this group have clinical insomnia as defined by the DSM (Diagnostic and Statistical Manual of Mental Disorders), which is about double the rate in the general population (~10-15%). Husak 2020
We’ve already discussed defining persistent pain, and a similar discussion is needed for insomnia. Currently, the DSM classifies insomnia based on a multi-pronged approach:
1. Dissatisfaction with sleep quality or quantity with:
Difficulty initiating sleep
Difficulty maintaining sleep (frequent awakenings or problems returning to sleep post-awakenings)
Early-morning awakening with inability to return to sleep
2. Duration of symptoms occur at least 3 days per week for ≥ 3 months
3. Sleep disturbances lead to significant distress or impairment in social, occupational, educational, academic, behavioral, or other functionally related areas
4. Sleep disturbances continue to occur in spite of adequate opportunities for sleep
5. Insomnia not otherwise explained, for example, sleep-related such as narcolepsy or sleep apnea, medical conditions, mental disorders, or substance related (i.e. drug abuse or medication usage). DSM-5 Insomnia In this article, Husak et al assessed DSM-classified insomnia as well as sleep disturbances. Unfortunately, the difficulties we discussed with defining persistent pain are also an issue with sleep disturbances. The authors chose to follow Cheatle et al definition: low-quality sleep issues not otherwise medically explained (e.g. sleep apnea, restless leg syndrome, etc.).