Insomnia Until it Hurts
The role of sleep deprivation in chronic pain, especially muscle pain
Paul Ingraham • updated Aug 29, 2020
We are used to thinking of insomnia as a symptom of stress — and it is.12 However, it is also hazardous in its own right. In this article I’ll discuss what little is known, and what we might reasonably guess, about the relationship between sleep disturbance and pain, especially the murky concept of muscle pain.3
xkcd #1345 © xkcd.com by Randall Munroe
The general biological importance of sleep
Certainly serious insomnia is nothing to mess around with. Insomnia is not generally fatal, of course, because there are all kinds of self-preservation mechanisms that kick in. But unchecked sleep deprivation is so serious that it can actually kill. Laboratory animals subjected to extreme sleep deprivation can die relatively swiftly of unknown causes — exactly what goes wrong is not clear, but their body temperatures start to drop and then they suffer rapid and widespread physiological failure. So sleep is actually required for life — for all life, in fact. Virtually every living organism sleeps — even simple ones without brains or nervous systems, or extremely simple ones, have circadian rhythms with distinct rest phases.
This strongly suggests that sleep-deprivation is potentially dangerous stuff, even when it isn’t lethal. A poison at a non-fatal dosage is still poisonous.4 And in fact there is a considerable amount of science confirming this general hypothesis. In his 1996 book, Sleep Thieves: An eye-opening exploration into the science and mysteries of sleep, Dr. Stanely Coren describes sleep deprivation studies in humans showing a number of ominous effects, and he generally makes a strong case that everyone needs to take sleep deprivation much more seriously than we generally do. Here are some other examples from much more recent scientific research:
Insomnia causes migraines. A study of 1869 migraines clearly showed that “sleep obviously protects against [migraine] attacks rather than provokes them,” while a whopping 29% were actually caused by insomnia. I don’t know about you, but anything that protects against migraine attacks is good and I don’t want to lose much of it.5
Insomnia makes you vulnerable to infections. We know that immunity is “tuned” by sleep6 (among other things). A statistical analysis of insomnia’s relationship to absences from work caused by illness clearly found that there’s a connection: insomnia is followed by periods of increased absenteeism from illness and disease.7 Yikes. Even more disturbing? The evidence shows that the effect is prominent up to two years after insomnia! •shudder•
Insomnia makes you sick in the long term, too. Sleep disturbance is associated with “a wide array of perturbations spanning from obesity, insulin resistance, type 2 diabetes, the metabolic syndrome, and cardiovascular disease risk and mortality in both adults and children.”8 Metabolic syndrome does its dirty work via subtle systemic inflammation, which may be a driver of chronic pain in some people (although normal associated with obesity and inactivity, metabolic syndrome also occur in fitter people as well, due to factors like insomnia, stress, anxiety, depression).
Insomnia can wreck your mood. 40% of psychiatric mood disorders are preceded by insomnia, and insomnia sets in at the same time as another 20% of mood disorders.910
Insomnia impairs athletic performance, getting more sleep boosts it,11 and injury rates and recovery are probably affected too.12
And still more! Roth et al summed some of this up: “Chronic insomnia is associated with absenteeism, frequent accidents, memory impairment, and greater health care utilization. The most consistent impact of insomnia is a high risk of depression.”13
So sleep deprivation involves some ominous potential hazards. But what about pain?
Is insomnia painful?
Yes. “According to the majority of the studies, sleep deprivation produces hyperalgesic changes.”14 Here’s a persuasive selection of many research examples:
In early 2019 (surprisingly late in history), we finally have the first proper brain study of sleep deprivation, one of those studies that looks at what parts of the brain “light up.”15 Although pain doesn’t happen in just one area of the brain, there are specific areas responsible for certain major features of pain. Sleep deprivation boosts responses to pain “within the primary sensing regions of the brain’s cortex,” and — more sinister — suppresses activity in the areas we use to “fine tune” pain experiences (“regions that modulate pain processing-the striatum and insula”). And that is a hellish cocktail: louder pain alarms, and less ability to mute them.
To anyone who has lost a lot of sleep, that sounds very familiar. Stepping on lego in your bare feet is just a lot worse when you’re exhausted.
As if that wasn’t bad enough, the same study also found that even “subtle” sleep disruptions can causes “consequential” changes in pain. It doesn’t take much.
A major driver of chronic pain is sensitization, basically turning up the “volume” on all pain.16 The phenomenon is well-known, but how it works is still a mystery, and its relationship with sleep has barely been studied. A 2016 experiment looked carefully 133 patients with knee arthritis, comparing those who slept well versus those who did not. They found, with a high degree of certainty, that “sleep fragmentation may strongly affect the pain and CS relationship; consequently, these results underscore the importance of considering and treating sleep in patients with chronic pain.”17
The issue with fragmentation came up in a 2007 study: Smith et al experimentally messed with the sleep of 32 innocent women, and found that they were significantly more pain-sensitive, finding that the effect was caused by sleep discontinuity, not deprivation alone (most insomniacs face both problems).18
What about the chicken/egg thing: which comes first, pain or sleeplessness? Once you have both insomnia and pain, they surely do cause each other, but one side of that equation is probably more important than the other, like a cyclist pushing much harder on one pedal than the other.Once you have both insomnia and pain, they surely do cause each other, but one side of that equation is probably more important than the other, like a cyclist pushing much harder on one pedal than the other. In 2017, Gerhart et al studied the which-came-first question of pain and insomnia in 105 chronic low back pain patients. The answer was decisive: pain followed sleeplessness much more than the other way around.19
An internet survey of over 2,500 people with fibromyalgia (a chronic pain condition) showed that insomnia was one of the most commonly identified aggravating factors.20 Whatever fibromyalgics find uncomfortable may be moving healthier people in the direction of increased sensitivity as well — they are a canary in the neurological mine. Simply put, if sleep deprivation does hurt, then fibromyalgics will notice it more readily than other people, and this is at least consistent with the fact that fibromyalgics believe that sleeplessness aggravates their symptoms.
Another survey found the fairly spectacular statistic that 53% of chronic low back pain patients had insomnia, compared with only 3% in pain-free controls.21 Critical thinkers might suggest that it’s most likely that low back pain that is keeping these people awake, but I don’t think that’s obvious at all. The jury must remain out for me. My clinical experience suggests that it’s just the opposite: chronic low back pain patients are often poor sleepers, and insomnia may routinely precede episodes of pain! All of this is also discussed in advanced low back pain tutorial.
And fortunately I’m not alone in this fairly counterintuitive idea. Kundermann et al write, “Although it is well documented that subjects with different pain syndromes suffer from sleep disturbances, the direction of cause and effect in this relationship is still a matter of debate.”22
There hasn’t been much data on this topic outside of wealthier populations. A 2018 study went further abroad and looked at links between pain and severe sleep problems in many poorer populations.23 The data set was humungous, and the results were vivid: pain and sleep problems were strongly linked, and it is definitely not just a case of the “worried well” sweating the little stuff in our relatively cushy lives. The sleep-health link matters no matter where you’re from.
People who hurt cannot sleep and vice versa — and that’s true globally.
If insomnia does cause pain, the costs are even more serious
Can pain shorten your life? It’s a plausible and disturbing possibility.
A large Swedish study of four million Swedes looked for a correlation between increased mortality and work absenteeism due to painful musculoskeletal conditions.24 The costs of pain are often expressed in terms of hair-raising stats on the economics of work absenteeism — but they may be much greater still.They found the first ever evidence that people who have musculoskeletal pain may have “an increased risk of premature death.” The researchers adjusted their data for “several potential confounders.” The costs of pain are often expressed in terms of hair-raising stats on the economics of work absenteeism — but they may be much greater still.
Pain and insomnia are clearly the perfect ingredients not only of a vicious cycle, each one worsening the other, but potential a dangerous one. The stakes are high.
Sleep loss is inflammatory, and inflammation makes us lose sleep (and all of that is bad for our biology)
Sleep loss is probably terrible for our health in general because it’s inflammatory… and, because life is unfair, inflammation probably also makes it harder to sleep. Ugh.
The link between sleep and pain is partly based on some superficially simply inflammatory biology: bad sleep is inflammatory… and inflammation makes it harder to sleep, which is not so widely appreciated. That means that sleeping badly can actually make it harder to sleep well!25 This is a vicious cycle every extremely frustrated insomniac is all-too familiar with: being exhausted from a sleepless is not a guarantee that you will sleep well the next night.26
So inflammation and sleep deprivation reinforce each other, and that vicious cycle is obviously in turn relevant to every kind of health problem that is mediated by inflammation, which appears to be most of them.
Do things really hurt more? Or does it just seem that way?
This is a thorny question, almost a philosophical one. It is well agreed in pain science that “seeming” is the whole ball of wax, the only thing that really matters: if something seems painful, it is. But we can still observe that some seemingly painful things are associated with measurable changes in tissues, while other seemingly painful experiences seem to occur in the absence of any such changes, and this difference is obviously of interest, and we’d like to identify it if we can. For instance, we mostly know about trigger points because they hurt, but only relatively recently in medical history have we begun to identify the tissue changes associated with that pain!
The lack of such signs in the tissues does not indicate an imaginary or hysterical pain, but either that we simply can’t identify an associated change in the tissues, or the difference exists in the complex functioning of the central nervous system itself — not so much a pain that’s “all in the your head” in the psychological sense, but a pain that’s “all in your brain and spinal cord.”
And all pain is also mediated by psychology. There is no such thing as pain that is “all in your body” — it’s impossible. See Pain is Weird for more about that interesting idea.
In 2004, Kundermann et al tried specifically to approach this question of whether or not pain associated with sleep deprivation involves an “organic” change in the tissues, or is simply a difference in how painful things seem. They tested whether or not sleep deprivation changed perception in general or only pain perception. The result was definitely the latter. Pain sensitivity was increased without any other general effects on physical sensations, strongly suggesting that something “actually” hurt more, as opposed to just “seeming” that way (“without alteration of somatosensation in general”).
The authors concluded, “Because this suggests an effect truly specific for pain, research may now focus on its underlying mechanisms of action.”27
Such as …
The case for insomnia as an aggravator of trigger points specifically
Insomnia doesn’t just cause pain in general, and it doesn’t do it just by mucking with the volume of all your nerves. It probably causes “musculoskeletal pain” specifically. We’ve already given the examples of the effects on fibromyalgia patients and migraine sufferers. But insomnia is also a likely cause of increased muscle pain in normal, healthy people.
Quick muscle knot orientation: So-called “muscle knots” — AKA trigger points — are small unexplained sore spots in muscle tissue associated with stiffness and soreness. No one doubts that they are there, but they are unexplained and controversial. They can be surprisingly intense, cause pain in confusing patterns, and they grow like weeds around other painful problems and injuries, but most healthcare professionals know little about them, so misdiagnosis is epidemic. For more information about how trigger points might be involved in your own medical history, see PainScience.com’s best-selling tutorial:
The Complete Guide to Trigger Points & Myofascial Pain An extremely detailed guide to the unfinished science of muscle pain, with reviews of every theory and treatment option ~ 152,500 words
Moldofsky et al’s sleep deprived subjects “reported more musculoskeletal symptoms” and “a significant increase in muscle tenderness.”28 The same researchers repeated those results in a second study.29 In 1999 Lentz et al found in their sleep-deprived subjects a whopping “24% decrease in musculoskeletal pain threshold.”30 That’s tenderness in the muscles specifically — sensitivity to poking or “mechanical” stimualtion — as opposed to sensitivity to cold or heat as is the case in many of the studies mentioned previously.
Another sleep-deprivation study of nine men in 2001 showed that pain sensitivity increased 8% with a “sleep debt” of 40 hours (40 hours of lost sleep with no opportunity to recover). Even more interesting, letting them catch up actually had a much greater pain-relieving effect — “greater than the analgesia induced by level I analgesic compounds.” Cool!31
And so on.
We are still a long way from proving that insomnia affects trigger points specifically or directly. None of these studies even begin to try to correlate pain sensitivity and musculoskeletal symptoms with trigger points specifically. And how could they? A lot of the scientific know-how needed to reliably measure the presence and severity of trigger points is barely any older than this sleep research, and only a few people on Earth have it.
But there is plenty of reason here to make an educated guess that a lot of that increased sensitivity is related to trigger point formation. If we pull back from the science for a moment and think about our subjective experience, if we know that most pain and stiffness is caused by trigger points, then we also know that sleep loss makes them worse: who hasn’t had the experience of having a bad night and feeling distinctly stiffer, achier, more sensitive to pressure? Who hasn’t noticed that it is precisely such a morning when you are most likely to suffer from at least a tension headache, if not a migraine as shown in one of the studies mentioned earlier? Who hasn’t wished especially hard for a good shoulder squeeze after sleeping badly?
These common experiences are definitely consistent with trigger point aggravation. It is likely that there is a whole mess of physiology and psychology that produces those effects, numerous factors above and beyond trigger points alone. But it is also quite reasonable to imagine that the effect is dominated by a straightforward worsening of the same pain and stiffness caused by trigger points that we feel even when we’ve slept perfectly well. And this would be a good use of occam’s razor (Wikipedia) — let’s not make this too much more complicated than it has to be!
A personal example: acute sleep deprivation causes extra muscle soreness after sports (quite a lot extra)
Ultimate is an intense Frisbee sport that can make almost anyone wicked sore.
The first ultimates games of the season have always been an ordeal. They are followed by 3-5 days of harsh delayed-onset muscle soreness. But in 2011 I started the season in unusually good physical condition, thanks to months of sprint intervals and strength training. For the first time ever I was not sore after my first games of the summer. And my DOMS-immunity continued in week two, so it didn’t seem to be a fluke.
That was then followed by some nasty sleep deprivation and jet lag. I suffered a great deal of it for two weeks — before, during and after a holiday to Amsterdam. When I returned to Vancouver and played ultimate again, I was really blasted sore. Quite extreme!
Coincidence? I think not. The scientific evidence is strong that sleep deprivation and disruption are major factors in chronic pain. This is the best example I’ve observed in the laboratory of me!
More personal perspective
I turned to a career in massage therapy in the late 90s largely because I was (and still am) an unusually “triggery” person. I am one of those people who just seems to have more than his fair share of trigger point discomfort. I relate well to my patients. I have been highly motivated to learn study the phenomenon of muscle pain.
In 2005, when I suffered from a particularly long and severe bout of insomnia, sleeping less than 4 hours per night for many weeks at a time, I experienced an inexorable increase in pain of all kinds, but especially trigger point pain. Every familiar old knot became loud and then vicious, and without question these sensations became the single most debilitating consequence of my insomnia.
Like Carl Sagan famously suggested, I try not to “think with my gut” and patiently wait for science to clarify the situation, one study at a time — it is okay to be uncertain. But if there is a topic in musculoskeletal health care that I have a “hunch” about, it’s this: insomnia is probably food for trigger points!