The study was led by Timothy A. Roehrs, Ph.D. of the Sleep Disorders and Research Center at the Henry Ford Hospital and supported by the Fund for Henry Ford Health System. Roehrs and his colleagues studied 18 pain-free, but mildly sleepy volunteers.
For the study, the participants were randomly assigned to four nights of either their normal amount of sleep, or extending their sleep time to 10 hours in bed per night. Their daytime sleepiness was measured on days one and four using the Multiple Sleep Latency Test (MSLT), a tool that measures how quickly a person falls asleep. Their pain sensitivity was also measured using finger withdrawal latency pain testing to a radiant heat stimulus.
The first study to prove sleep reduces pain.
The results of the study were published in the Dec. 1 issue of the journal Sleep. It is the first research of its kind to prove that extended sleep in mildly sleep-deprived adults can significantly reduce their sensitivity to pain.
The results showed that the extended sleep group—those who slept more than normal—slept 1.8 hours more per night than the normal sleep group. It also showed that they experienced less daytime sleepiness. This increase in sleep time during the four nights correlated to increased daytime alertness, as well as less sensitivity to pain.
Regarding the pain test, the extended sleep group showed a greater tolerance for pain/reduced pain sensitivity. The length of time before participants removed their finger from a radiant heat source increased by 25 percent. The researchers noted that this increase in “finger withdrawal latency” is greater than the effect found in a previous study where participants used 60 milligrams of codeine.
In their report, the researchers stated that the results, combined with data from previous research, suggest that increased pain sensitivity in sleepy individuals is the result of their underlying sleepiness.
Timothy Roehrs, PhD, the study’s principal investigator and lead author said, “The results suggest the importance of adequate sleep in various chronic pain conditions or in preparation for elective surgical procedures. We were surprised by the magnitude of the reduction in pain sensitivity, when compared to the reduction produced by taking codeine.”
Read the press release for the study, “Extended sleep reduces pain sensitivity.”
Lack of sleep and an increase in strokes.
Roehrs’ study adds to growing evidence that more regular, restorative sleep can help reduce the risk of health problems, and the opposite is true, as well.
Last June, the University of Alabama at Birmingham released the results of a study that regularly sleeping less than six hours a night significantly increases the risk of stroke symptoms in middle-age to older adults who are of normal weight and at low risk for obstructive sleep apnea (OSA). That’s worth repeating: Less than six hours of sleep per night increases the risk of strokes in adults of normal weight and not at risk for OSA.
It seems that under six hours of sleep per night is the critical variable, but why? Let’s take a look at the study. The University of Alabama researchers followed 5,666 people for up to three years who had no history of strokes or stroke-like symptoms, transient ischemic attacks (when blood flow to the brain stops for a brief period causing stroke-like symptoms), or high risk for OSA at the start of the study.
For a period of three years, the researchers followed and studied the subjects’ first stroke symptoms, stroke risk factors, depression symptoms, demographic information and other various health behaviors. What they found was—after adjusting for body-mass index (BMI)—there was a strong association between daily sleep periods of less than six hours and a greater incidence of stroke symptoms for middle-age to older adults, even beyond other risk factors. Interestingly, the researchers did not find any link between short sleep periods and stroke symptoms in overweight and obese participants.
Still, the connection between short sleep and strokes is worthy of great attention from the medical community and general public. I agree with the Alabama study’s lead author, Megan Ruiter, PhD., who said, “The results of the Alabama study provide a strong argument for increasing physician and public awareness of the impact of sleep as a risk factor for stroke symptoms, especially among persons who appear to have few or no traditional risk factors for stroke.”
It looks like the medical community is taking this message to heart, no pun intended. Another study announced in late July is going on at the Alberta Health Services and the University of Calgary. There, Dr. Patrick Hanly of the university’s Hotchkiss Brain Institute is leading a study to learn more about the physiological connection between sleep apnea and stroke—specifically, the brain’s blood flow response in people with and without sleep apnea.
For the study, participants with sleep apnea stay overnight in the sleep laboratory at Calgary’s Foothills Medical Centre, where their breathing and cardiovascular responses are continuously monitored while they sleep. The next day, their brain blood flow response to reduced oxygen levels is assessed while they are awake. Then, the participants receive supplemental oxygen during sleep for two weeks, and are tested again to see if their cerebral defense mechanisms have improved. The researchers are also studying people without sleep apnea to see if their cerebral defense mechanisms function better than in those with sleep apnea. Hanly and team’s theory is that it is the lack of oxygen, or hypoxia, that people with sleep apnea experience during sleep that impairs the body’s normal defense mechanisms in the brain. A better understanding of this connection will lead to better prevention and treatment strategies.
I applaud the work of the Alabama and Calgary researchers. It’s time we all wake up to the health benefits of regular, restorative sleep
For more information, read the University of Alabama at Birmingham study, “Under 6 Hours of Sleep Tops Risks for Stroke in a Low-risk Population.”
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