Sleep is a biological necessity, and its importance in promoting quality of life and well-being is well documented. Thus, sleep deprivation leads to fatigue, excessive daytime sleepiness and cognitive impairments (such as verbal fluency, memory, decision-making, and reaction time)BLOOM; AHMED; ALESSI; ANCOLI-ISRAEL et al., 2009Among the factors that lead to sleep deprivation and sleep restriction, persistent pain is one of the most common reasonsBRENNAN; LIEBERMAN, 2009Thus, many patients believe that the sleep problems they experience are due to the pain they feelHAWKER; STEWART; FRENCH; CIBERE et al., 2008Still, many patients believe that the pain will disappear when the sleep problem is resolvedMORIN; GIBSON; WADE, 1998Therefore, the purpose of this article is to demonstrate the relations between pain and sleep issues.
Relation between sleep and pain
Sleep deprivation leads to changes in pain processing, so that chronic sleep restriction increases pain sensitivityKUNDERMANN; KRIEG; SCHREIBER; LAUTENBACHER, 2004For example, healthy subjects reported pain amplification after 2 nights of sleep restriction (whose nocturnal sleep was restricted to 4h), and perceived pain intensity increased with the number of nights of sleep restrictionHAACK; MULLINGTON, 2005In seven healthy subjects, sleep restriction and REM sleep restriction caused hyperalgesia the next dayROEHRS; HYDE; BLAISDELL; GREENWALD et al., 2006These authors conclude that it is important to exercise caution when administering medications that reduce both total sleep time and/or the proportion of REM sleep during the night, as this may increase individuals' pain sensitivity.
hus, this evidence indicates that acting with a focus on improving sleep quality can be an effective strategy to alleviate pain in these patients. Still, good quality sleep is considered essential in the resolution of persistent painDAVIES; MACFARLANE; NICHOLL; DICKENS et al., 2008and, in addition, patients with persistent pain who are good sleepers report less pain at nightASHWORTH; DAVIDSON; ESPIE, 2010Thus, sleep and pain are directly related when one or the other increases or decreases.
Effects of pain in sleep
Insomnia is defined as sleep onset latency greater than 30 minutes and/or nighttime awakening greater than 30 minutes with a frequency equal to or greater than 3 days a week and duration equal to or greater than 3 monthsSATEIA, 2014Insomnia is highly prevalent in patients with chronic pain, so that 53 to 90% have some degree of clinical insomniaTANG; WRIGHT; SALKOVSKIS, 2007For example, patients who suffer from chronic back pain are 18 times more likely to have insomnia than people who do not present back pain.
Also, constant pain generates disorders and changes in the person's lifestyle that, ultimately, result in a worsening of sleep quality. For example, patients with chronic pain often have reduced levels of daily physical activity and increased bedtime and naps during the day. This pattern of activity can promote and perpetuate insomnia through conditioningSPIELMAN; SASKIN; THORPY, 1987In a cross-sectional study conducted on patients with hip osteoarthritis awaiting hip arthroplasty, more than 50% of these patients suffered from insomnia. On the other hand, pain reduction improved sleep quality in half of these patientsBLÅGESTAD; PALLESEN; GRØNLI; TANG et al., 2016The same fact was observed in patients with rheumatoid arthritis, supporting the impact of sleep restriction on pain severityIRWIN; OLMSTEAD; CARRILLO; SADEGHI et al., 2012In addition, chronic pain is associated with other health conditions, such as increased risk for developing depression, frequent use of medication, poor quality of life and greater use of the health systemBLAY; ANDREOLI; GASTAL, 2007).
Management of chronic pain and sleep disorders
Despite the growing increase in scientific literature involving the topic of sleep in patients with chronic pain, many pain management programs use analgesics and/or hypnotics to treat comorbidities such as insomniaTANG; WRIGHT; SALKOVSKIS, 2007These medications include anticonvulsants, benzodiazepines and non-benzodiazepines, and tricyclic antidepressants. However, it is important to be careful when administering these drugs, since they have side effects. For example, the use of hypnotic medications is related to side effects such as sedation, excessive daytime sleepiness, dizziness, headache, and cognitive and psychomotor impairmentsHOLBROOK; CROWTHER; LOTTER; CHENG et al., 2000In addition, there is evidence demonstrating that medication in people with headache or musculoskeletal pain can worsen sleep and thus increase the sensation of painDOUFAS; PANAGIOTOU; IOANNIDIS, 2012Thus, it is critical that the patient's condition is analyzed and the root of the pain is effectively treated and, in parallel, if necessary, a medication that promotes the least harm possible is administered.
he vast majority of patients with chronic pain have some degree of sleep impairment. On the other hand, sleep restriction causes a worsening in the perception of pain. Thus, these patients need a differentiated treatment that addresses both the root of the pain and the existing sleep disorders. Finally, it is necessary to be cautious regarding the use of hypnotic drugs, since the possible side effects can directly impact the daily lives of these patients
How to assess sleep?
Actigraphy is a technique that can be used to assess sleep pattern and sleep-wake rhythm. The actigraph is a wristwatch-like device that contains light, motion, and temperature sensors. Thus, through this information, it is possible to extract data on variables such as total sleep time, sleep onset latency, time awake after sleep onset, sleep efficiency, time awake and variables related to rhythm, such as cosinor, spectrogram. , periodogram, and non-parametric variables such as L5, M10, IS and IV.