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From Classic Sleep Care

“Everybody talks about the weather, but nobody does anything about it,” is usually attributed to Mark Twain but may have originated with a friend of Twain’s Charles Dudley Warner. Temperature effects on sleep seem to mirror this sentiment for many sleep disorders’ patients, who frequently complain about being too hot or too cold and cannot find satisfactory solutions to the dilemma. Although in this post no “cures” are offered, a number of strategies could be considered and implemented that have been known to make a difference in many cases.

To start, knowing something about temperature issues in the two most common sleep disorders, insomnia and sleep apnea, will assist your efforts. Although you know from other posts a surprisingly large overlap occurs between these two disorders, yet it is an individual’s perception of his or her chief sleep complaint that predicts how temperature issues affect slumber.

Insomnia patients by definition suffer either from frank anxiety or “somatized tension,” a technical term indicating the individual has difficulty experiencing emotions, such as anxiety, and instead stores the feelings as physical tension in the body. As you might imagine, an insomniac’s tenseness or tension correlates with adverse changes in the nervous system. You would expect a chronic insomniac to experience above average resting heart rates, elevations in blood pressure and even faster breathing rates. The tension manifesting in these three examples affects the heart, overall circulation, and respiration. For all these changes to occur requires activation of the sympathetic nervous system (which in extreme circumstances generates a fight or flight response) targeting key organs in the body. Among insomniacs, sympathetic activation often vasoconstricts blood vessels in the periphery of the body (meaning farthest from the heart), that is, the hands and feet. With less blood in the arms and legs, sooner than later the insomniac reports cold hands and cold feet. This patient must do something to warm up, because going to bed cold is very uncomfortable and aggravates sleeplessness.

The sleep apnea patient has the opposite problem in which higher temperatures worsen breathing. A few studies as far back as the 1980s and 1990s demonstrated cold air improves breathing. A couple studies suggested Fahrenheit temperatures in the mid to upper 50 degree range was optimal for normalizing breathing. You can imagine of course the individual would need to find a way to stay warm throughout the night, which then raises the question of whether or not such efforts to bundle up would diminish the effect of an ambient room temperature of say, 59 degrees? As an aside, in our intake system, we ask individuals whether they notice difficulty sleeping in a warm and stuffy room, and it is interesting how many patients report this exact experience despite presenting to the sleep center without any breathing complaints save snoring. Nearly all these patients turn out to suffer from previously undiagnosed sleep apnea; yet, many sought treatment for the problem of insomnia.

These are the two main scenarios: the insomniac wants it warmer, and the sleep apneic wants it colder. Put the two disorders into the same person, and instead canceling things out, the outcome is more like double trouble. Nonetheless, there are strategies to attempt to lessen the effects of temperature for each disorder or in combination.

For the insomniac, artificially warming the four extremities of the body yields very interesting and consistent results. When an individual bathes in a warm to hot tub before bedtime, it will not only raise body temperature but also eliminate the vasoconstriction in the hands and feet. Thus, the insomniac slips into bed with no cold-related discomfort. Moreover, since most but not all vasoconstriction subsides during sleep, the insomniac might sleep all through the night without suffering cold hands or feet. The use of the hot bath has been studied and consistently shows most individuals with insomnia report improvements.

Moreover, another facet of temperature specific to insomniacs likely explains the improved sleep from artificially increasing body temperature near bedtime. Due to their sympathetic activation, insomniacs may experience slight elevations in their normal baseline temperature (not a fever, just higher than average); and, one current theory indicates the temperature of the insomniac does not drop near sleep onset or during the night. This static temperature may be highly problematic, because part of the sleep onset cycle appears related to the release of melatonin into the body, and germane to our discussion, a melatonin spike co-occurs to some extent with the body’s natural drop in temperature at bedtime and through part of the night. Indeed, this theory suggests that the sleepiness triggered by temperature drops not only causes you to fall asleep but it also sustains sleep through the night. Halfway or two-thirds of the way through the night, temperatures start to rise and facilitate awakening in the morning.

Insomniacs may suffer from this problem without realizing it, because it would be unusual for someone to track body temperature so closely. Remarkably, because the hot bath seems to raise the body’s temperature artificially, it means the temperature can now fall further than under the individual’s normal circumstances, and then this “deeper” drop in temperature facilitates the onset of sleepiness feelings. In the same vein, it is not unusual for an insomniac to resort to a heating blanket, and the worthy attribute of this device is the rapid ability to turn it off in the middle of the night when the higher temperature becomes counterproductive to maintaining sleep. Then again, this step might trigger a new bout of insomnia if the individual is particularly sensitive to even the shortest awakenings. Nowadays, such electric blankets would have timer systems that might resolve this issue.

For the patient with clear-cut sleep apnea without co-occurring insomnia, finding a cooler temperature is a priority. Even though current treatment might be PAP or OAT, this type of patient still prefers cooler temperatures. The simplest steps taken are usually lowering the temperature with stronger air conditioning effects (summer), lowering the heating effects (winter), or use of outside temperature effects by open windows (seasonally). Two additional common techniques are the limitations on bedclothes and bed linens. Arguably, the majority of sleep apnea patients have already learned to take these steps because of past experiences before ever having received treatment for the condition. However, some patients need education on these simple steps, and once applied, they will usually report clear benefits by lowering the temperature in the bedroom either through the mechanical efforts of heating, cooling and window systems or evaporative loss of heat through fewer clothes and blankets.

Remarkably, just opposite to the insomniac’s situation, the sleep apnea patient could purchase a cooling blanket. This technology is in early stages of development, but several products are available, and some include the capacity for warming and cooling in the same device, see:

Long-term expectations are that this technology will gain huge market share, because the dynamic nature of sleep cycles clearly indicates variation in temperature through the night. Indeed, during REM sleep there is a relative loss of thermoregulation capacity of which one distinctive feature is a rise in brain temperature combined with a potential for a cooler body due to muscle atonia (loss of muscle tension). As more research is gathered, it would not be surprising to see the development of various devices for heating or cooling specific parts of the body with adjustable or timed effects throughout the night. Think about the “Power Nap Head Pillow” and imagine all the extras that might be added to influence temperature adjustments.

The last area of concern for the sleep apnea patient is how to manage the PAP humidifier. Moisturizing air is essential for the vast majority of PAP users, although some patients dislike humidification altogether or some prefer pass over cold humidification. As important as humidifying the air is for most patients, there can still be a problem with too much heat generated by the device. This problem arises specifically with patients who want maximum humidification, which means using the highest settings and water temperatures on the humidifier chamber. As you would expect, the higher the settings and temperature ratings, the more heat is delivered into the airway along with moisturized air. This effect is discernible to most patients who feel overly sensitive to temperature changes. So, in the sleep apnea patient who likes the bedroom very cold, this individual needs to fastidiously sort out how high the humidity settings can go without creating too much of a “warm air” sensation that foils the effects of the cool bedroom. Further complicating this effort, the cold air in the bedroom may cause the moisturized air in the PAP tube to condense into water droplets, and then water splashes into the nose and throat (an unforgettably unpleasant sensation!). Wrapping the PAP tube may protect against this phenomenon.

Finally, there are patients with comorbid insomnia and OSA/UARS. In some ways, these circumstances should be the trickiest to manipulate due to the opposing temperature requirements of each disorder, but as it turns out, it may just be a matter of timing the priorities to suit the specific disorder. For example, the insomnia portion may still benefit from raising the temperature in a hot bath or shower before bedtime to eliminate the vasoconstriction in the hands and feet. Once asleep, this same person should benefit from an overall cooler ambient temperature that supports better breathing. In the next phase of sleep, however, what if the cooler temperature creates susceptibility to vasoconstriction and colder extremities. If the temperatures in the room go too low, perhaps the insomnia portion takes over and awakens the patient. Still, a perfect convergence of factors can materialize to save the day (er, night!): the patient could learn to ramp up the humidification to a level that moisturizes the air, but which maintains enough heat to prevent changes in core body temperature and yet remains low enough to facilitate better breathing. Throughout, this individual will most likely factor in different bedclothes and bed linen scenarios to further tweak the system. Seasonally, a person might need to discover a pattern that works well for each period; whereas, those living in climates with modest variation may find making these adjustments much easier.

As complicated as some of these steps might seem, they are well worth your efforts if you suffer from sleep disorders of insomnia or OSA/UARS, because your risks for temperature-driven changes in your sleep are very high. Learning to combat these temperature effects in your bedroom or in your own body will often dramatically change the quality of your slumber for the better.


Interesting References:

Dorsey CM, Lukas SE, Teicher MH, Harper D, Winkelman JW, Cunningham SL, Satlin A.

Effects of passive body heating on the sleep of older female insomniacs. J Geriatr Psychiatry Neurol. 1996 Apr;9(2):83-90.

Wehr TA. A brain-warming function for REM sleep. Neurosci Biobehav Rev. 1992 Fall;16(3):379-97. Review.


From Classic Sleep Care