Summary: Researchers report getting more sleep, and for those who can’t sleep, increasing caffeine uptake, can help relieve chronic pain better than standard pain killers.
Source: Boston Children’s Hospital.
In sleep-deprived mice, caffeine and other drugs to promote wakefulness ease pain better than analgesics.
New research from Boston Children’s Hospital and Beth Israel Deaconess Medical Center (BIDMC) shows that chronic sleep loss increases pain sensitivity. It suggests that chronic pain sufferers can get relief by getting more sleep, or, short of that, taking medications to promote wakefulness such as caffeine. Both approaches performed better than standard analgesics in a rigorous study in mice, described in the May 8, 2017 issue of Nature Medicine.
Pain physiologist Alban Latremoliere, PhD, of Boston Children’s and sleep physiologist Chloe Alexandre, PhD, of BIDMC precisely measured the effects of acute or chronic sleep loss on sleepiness and sensitivity to both painful and non-painful stimuli. They then tested standard pain medications, like ibuprofen and morphine, as well as wakefulness-promoting agents like caffeine and modafinil. Their findings reveal an unexpected role for alertness in setting pain sensitivity.
Keeping mice awake, through custom entertainment
The team started by measuring normal sleep cycles, using tiny headsets that took electroencephalography (EEG) and electromyography (EMG) readings. “For each mouse, we have exact baseline data on how much they sleep and what their sensory sensitivity is,” says Latremoliere, who works in the lab of Clifford Woolf, PhD, in the F.M. Kirby Neurobiology Center at Boston Children’s.
Next, unlike other sleep studies that force mice to stay awake walking treadmills or falling from platforms, Alexandre, Latremoliere and colleagues deprived mice of sleep in a way that mimics what happens with people: They entertained them.
“We developed a protocol to chronically sleep-deprive mice in a non-stressful manner, by providing them with toys and activities at the time they were supposed to go to sleep, thereby extending the wake period,” says Alexandre, who works in the lab of Thomas Scammell, MD, at BIDMC. “This is similar to what most of us do when we stay awake a little bit too much watching late-night TV each weekday.”
To keep the mice awake, researchers kept vigil, providing the mice with custom-made toys as interest flagged while being careful not to overstimulate them. “Mice love nesting, so when they started to get sleepy (as seen by their EEG/EMG pattern) we would give them nesting materials like a wipe or cotton ball,” says Latremoliere. “Rodents also like chewing, so we introduced a lot of activities based around chewing, for example, having to chew through something to get to a cotton ball.”
In this way, they kept groups of six to 12 mice awake for as long as 12 hours in one session, or six hours for five consecutive days, monitoring sleepiness and stress hormones (to make sure they weren’t stressed) and testing for pain along the way.
Pain sensitivity was measured in a blinded fashion by exposing mice to controlled amounts of heat, cold, pressure or capsaicin (the agent in hot chili peppers) and then measuring how long it took the animal to move away (or lick away the discomfort caused by capsaicin). The researchers also tested responses to non-painful stimuli, such as jumping when startled by a sudden loud sound.
“We found that five consecutive days of moderate sleep deprivation can significantly exacerbate pain sensitivity over time in otherwise healthy mice,” says Alexandre. “The response was specific to pain, and was not due to a state of general hyperexcitability to any stimuli.”
Analgesics vs. wake-promoting agents
Surprisingly, common analgesics like ibuprofen did not block sleep-loss-induced pain hypersensitivity. Even morphine lost most of its efficacy in sleep-deprived mice. These observations suggest that patients using these drugs for pain relief might have to increase their dose to compensate for lost efficacy due to sleep loss, thereby increasing their risk for side effects.
In contrast, both caffeine and modafinil, drugs used to promote wakefulness, successfully blocked the pain hypersensitivity caused by both acute and chronic sleep loss. Interestingly, in non-sleep-deprived mice, these compounds had no analgesic properties.
“This represents a new kind of analgesic that hadn’t been considered before, one that depends on the biological state of the animal,” says Woolf, director of the Kirby Center at Boston Children’s. “Such drugs could help disrupt the chronic pain cycle, in which pain disrupts sleep, which then promotes pain, which further disrupts sleep.”
A new approach to chronic pain?
The researchers conclude that rather than just taking painkillers, patients with chronic pain might benefit from better sleep habits or sleep-promoting medications at night, coupled with daytime alertness-promoting agents to try to break the pain cycle. Some painkillers already include caffeine as an ingredient, although its mechanism of action isn’t yet known. Both caffeine and modafinil boost dopamine circuits in the brain, so that may provide a clue.
“This work was supported by a novel NIH program that required a pain scientist to join a non-pain scientist to tackle a completely new area of research,” notes Scammel, professor of neurology at BIDMC. “This cross-disciplinary collaboration enabled our labs to discover unsuspected links between sleep and pain with actionable clinical implications for improving pain management.”
“Many patients with chronic pain suffer from poor sleep and daytime fatigue, and some pain medications themselves can contribute to these co-morbidities,” notes Kiran Maski, MD, a specialist in sleep disorders at Boston Children’s. “This study suggests a novel approach to pain management that would be relatively easy to implement in clinical care. Clinical research is needed to understand what sleep duration is required and to test the efficacy of wake-promoting medications in chronic pain patients.”
Alexandre (BIDMC) and Latremoliere (Boston Children’s) were co-first authors on the paper. Woolf (Boston Children’s) and Scammell (BIDMC) were co-senior authors. Ashley Ferreira and Giulia Miracca of Boston Children’s and Mihoko Yamamoto of BIDMC were coauthors.
Funding: This work was supported by grants from the NIH (R01DE022912, R01NS038253). The Neurodevelopmental Behavior and Pharmacokinetics Cores at Boston Children’s Hospital, the metabolic Physiology Core at BIDMC (P30DK057521) and P01HL09491 also supported this study.
Source: Bethany Tripp – Boston Children’s Hospital
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “Decreased alertness due to sleep loss increases pain sensitivity in mice” by Chloe Alexandre, Alban Latremoliere, Ashley Ferreira, Giulia Miracca, Mihoko Yamamoto, Thomas E Scammell & Clifford J Woolfn in Nature Medicine. Published online May 8 2017 doi:10.1038/nm.4329
[cbtabs][cbtab title=”MLA”]Boston Children’s Hospital “Caffeine and More Sleep Help Improve Chronic Pain .” NeuroscienceNews. NeuroscienceNews, 8 May 2017.
<https://neurosciencenews.com/caffeine-sleep-pain-6619/>.[/cbtab][cbtab title=”APA”]Boston Children’s Hospital (2017, May 8). Caffeine and More Sleep Help Improve Chronic Pain . NeuroscienceNew. Retrieved May 8, 2017 from https://neurosciencenews.com/caffeine-sleep-pain-6619/[/cbtab][cbtab title=”Chicago”]Boston Children’s Hospital “Caffeine and More Sleep Help Improve Chronic Pain .” https://neurosciencenews.com/caffeine-sleep-pain-6619/ (accessed May 8, 2017).[/cbtab][/cbtabs]
Decreased alertness due to sleep loss increases pain sensitivity in mice
Extended daytime and nighttime activities are major contributors to the growing sleep deficiency epidemic as is the high prevalence of sleep disorders like insomnia. The consequences of chronic insufficient sleep for health remain uncertain3. Sleep quality and duration predict presence of pain the next day in healthy subjects suggesting that sleep disturbances alone may worsen pain, and experimental sleep deprivation in humans supports this claim. We demonstrate that sleep loss, but not sleep fragmentation, in healthy mice increases sensitivity to noxious stimuli (referred to as ‘pain’) without general sensory hyper-responsiveness. Moderate daily repeated sleep loss leads to a progressive accumulation of sleep debt and also to exaggerated pain responses, both of which are rescued after restoration of normal sleep. Caffeine and modafinil, two wake-promoting agents that have no analgesic activity in rested mice, immediately normalize pain sensitivity in sleep-deprived animals, without affecting sleep debt. The reversibility of mild sleep-loss-induced pain by wake-promoting agents reveals an unsuspected role for alertness in setting pain sensitivity. Clinically, insufficient or poor-quality sleep may worsen pain and this enhanced pain may be reduced not by analgesics, whose effectiveness is reduced, but by increasing alertness or providing better sleep.
“Decreased alertness due to sleep loss increases pain sensitivity in mice” by Chloe Alexandre, Alban Latremoliere, Ashley Ferreira, Giulia Miracca, Mihoko Yamamoto, Thomas E Scammell & Clifford J Woolfn in Nature Medicine. Published online May 8 2017 doi:10.1038/nm.4329