Cooling And Thermo-Regulation

Andrew C. Gallup, Department of Psychology, State University of New York at Albany, Albany, NY 12222, USA.

Gordon G. Gallup Jr., Department of Psychology, State University of New York at Albany.

Abstract:
We conducted two experiments that implicate yawning as a thermoregulatory mechanism. The first experiment demonstrates that different patterns of breathing influence susceptibility to contagious yawning.

When participants were not directed how to breathe or were instructed to breathe orally (inhaling and exhaling through their mouth), the incidence of contagious yawning in response to seeing videotapes of people yawning was about 48%.

When instructed to breathe nasally (inhaling and exhaling through their nose), no participants exhibited contagious yawning.

In a second experiment, applying temperature packs to the forehead also influenced the incidence of contagious yawning. When participants held a warm pack (460C) or a pack at room temperature to their forehead while watching people yawn, contagious yawning occurred 41% of the time. When participants held a cold pack (40C) to their forehead, contagious yawning dropped to 9%. These findings suggest that yawning has an adaptive/functional component that it is not merely the derivative of selection for other forms of behaviour.

The next time you “catch a yawn” from someone across the room, you’re not copying their sleepiness, you’re participating in an ancient, hardwired ritual that might have evolved to help groups stay alert as a means of detecting danger. That’s the conclusion of University at Albany researchers Andrew C. Gallup and Gordon G. Gallup, Jr. in a study outlined in the May 2007 issue in Evolutionary Psychology.

The psychologists, who studied yawning in college students, concluded that people do not yawn because they need oxygen, since experiments show that raising or lowering oxygen and carbon dioxide in the blood fails to produce the reaction. Rather, yawning acts as a brain-cooling mechanism. The brain burns up to a third of the calories we consume, and as a consequence generates heat.

According to Gallup and Gallup, our brains, not unlike computers, operate more efficiently when cool, and yawning enhances the brain’s functioning by increasing blood flow and drawing in cooler air.

To research the theory that yawning evolved to cool the brain, the UAlbany psychologists had students watch videotapes of people yawning and counted the number of contagious yawns. In one experiment they found that 50 percent of the people who were instructed to breathe normally or through their mouths yawned while watching other people yawn, while those told to breathe through their nose did not yawn at all.

In another experiment they found that subjects who held a cold pack to their forehead acted similarly to those who were instructed to breathe through their nose — they, too, did not yawn, while those who held a warm pack or a room temperature pack to their forehead yawned normally.

Evidence shows that blood vessels in the nasal cavity and face send cool blood to the brain, and by breathing through the nose or by cooling the forehead, the brain is cooled, eliminating the need to yawn. Recent evidence has linked multiple sclerosis, a demyelinating disease, to thermoregulatory dysfunction. Excessive yawning is a common symptom of multiple sclerosis, and some MS patients report brief symptom relief after they yawn.

The UAlbany researchers also suggest, again contrary to popular opinion, that yawning does not promote sleep but helps mitigate the need to sleep. Since yawning occurs when brain temperature rises, sending cool blood to the brain serves to maintain optimal levels of mental efficiency. Therefore, the psychologists say, when mental processing slows and someone yawns, the tendency for other people to yawn contagiously might have evolved to promote group vigilance as a means of detecting danger.

So the next time you are telling a story and a listener yawns there is no need to be offended — yawning, a physiological mechanism designed to maintain attention, turns out to be a compliment.

Source: Evolutionary Psychology – 2007. 5(1): 92-101 (25/06/07)

A randomized controlled study of the acute and chronic effects of cooling therapy for MS

Neurology. 2003 Jun 24;60(12):1955-1960
NASA/MS Cooling Study Group

Background
Cooling demyelinated nerves can reduce conduction block, potentially improving symptoms of MS.

The therapeutic effects of cooling in patients with MS have not been convincingly demonstrated because prior studies were limited by uncontrolled designs, unblinded evaluations, reliance on subjective outcome measures, and small sample sizes.

Objective
To determine the effects of a single acute dose of cooling therapy using objective measures of neurologic function in a controlled, double-blinded setting, and to determine whether effects are sustained during daily cooling garment use.

Methods
Patients (n = 84) with definite MS, mild to moderate disability (Expanded Disability Status Scale score < 6.0), and self-reported heat sensitivity were randomized into a multicenter, sham-treatment controlled, double-blind crossover study.

Patients had the MS Functional Composite (MSFC) and measures of visual acuity/contrast sensitivity assessed before and after high-dose or low-dose cooling for 1 hour with a liquid cooling garment.

One week later, patients had identical assessments before and after the alternate treatment.

Patients were then re-randomized to use the cooling garment 1 hour each day for a month or to have observation only.

They completed self-rated assessments of fatigue, strength, and cognition during this time, and underwent another acute cooling session at the end of the period.

After 1 week of rest, they had identical assessments during the alternate treatment.

Results
Body temperature declined during both high-dose and low-dose cooling, but high-dose produced a greater reduction (p < 0.0001).

High-dose cooling produced a small improvement in the MSFC (0.076 +/- 0.66, p = 0.007), whereas low-dose cooling produced only a trend toward improvement (0.053 +/- 0.031, p = 0.09), but the difference between conditions was not significant.

Timed gait testing and visual acuity/contrast sensitivity improved in both conditions as well. When patients underwent acute cooling following a month of daily cooling, treatment effects were similar.

Patients reported less fatigue during the month of daily cooling, concurrently on the Rochester Fatigue Diary and retrospectively on the Modified Fatigue Impact Scale.

Conclusions
Cooling therapy was associated with objectively measurable but modest improvements in motor and visual function as well as persistent subjective benefits.

For further information, refer to the PubMed Report.

Wearing a cooling vest can help MS patients with muscle strength, fatigue and balance, according to a study published in Neurology, the scientific journal of the American Academy of Neurology.

"This is exciting, because it's a relatively easy treatment that brings an immediate benefit", said author and neurologist Jacque De Keyser, MD, PhD of the University Hospital in Groningen, Holland.

For the study, 10 patients whose symptoms respond to temperature changes wore the vests for an hour. Half the patients experienced active cooling, with a coolant at 45 degrees. As a control group, the other half experienced 'sham' cooling, with the coolant set at 79 degrees so the patient would feel a cool contact and would not know whether they were receiving the treatment or not. A week later, the groups were switched around.

Tests of the patients' fatigue level, balance with eyes shut and lower limb muscle strength were performed before the cooling, and again three hours after the session. The patients' temperatures were taken every 15 minutes.

Researchers also tested the blood of patients for white cell production of nitric oxide, a naturally-occurring molecule, before and then three hours after the cooling session.

After active cooling, balance improved by an average of 20%, muscle strength improved by 10%, and the level of fatigue also improved significantly, according to Dr Keyser. "The patients' temperature did not drop during the cooling."

Ref: American Academy of Neurology

For further information, refer to the BBC News article.

Wearing a cool suit reduces MS fatigue, say Swedish researchers.

They tested a suit that cools the head and upper body, reducing core temperature by between 0.1 and 1 deg C. The suits were used for four weeks. All 8 patients in the study reported a reduction in fatigue during the trial period.

Patients reported a reduction in the physical, cognitive and psycho-social impact of fatigue. Fatigue was experienced less often and for shorter periods.

The authors say that the cooling suit is practical, gives freedom and flexibility and can be used in any setting.

Ref: Flensner G, Lindencrona C (2002) The cooling suit: case studies of its influence on fatigue among eight individuals with multiple sclerosis. Journal of Advanced Nursing. 37, 6, 541-550. Source: Nursing Standard, May 31st 2002.

In the Cooling Vest study, the researchers found that MS patients had higher leucocyte nitrite concentrations than controls. The cooling reduced nitrite concentrations by 41% in MS patients; this was not observed in the 'sham' Group.

Dr De Keyser thinks that nitric oxide may contribute to MS symptoms by reducing axonal conduction of demyelinated axons. He said, "If this symptomatic improvement is due to a reduction of leucocyte nitric oxide production, then pharmacological interventions could be developed that achieve the same effect."

Ref: The Lancet. Vol. 358. September 15, 2001.

Symptoms of MS improve after acute cooling sessions, researchers have found. The trial involved 84 MS patients. All were evaluated for MS symptoms before and after undergoing first an hour of high-dose acute cooling and then an hour of low-dose acute cooling with a liquid cooling garment.

Patients were divided into two groups. One used the cooling garment at home for one hour a day for one month, while the other did not. All the patients completed detailed surveys on symptoms.

Following the one-month period, they were again assessed before and after the acute cooling sessions. The high-dose cooling did produce a greater reduction in body temperature when compared with the low dose cooling.

Patients who underwent daily cooling at home also reported a slight reduction in motor and visual symptoms and less fatigue. All patients demonstrated some improvements after the acute cooling sessions, regardless of whether they received the high or low-dose cooling.

Ref: Neurology, 2003;60:1955-1960