How to Become Smarter (23 page)

You can use the cold shower for the head (the head shower) as follows. Insert earplugs, set water temperature to about 20°C (68°F), kneel by the tub or shower stall, and tilt your head so that it is horizontal, face down. You can now apply the cold shower to the head, but avoid wetting the neck. Adjust the flow of water to a comfortable level. If you do not use the earplugs, the water will enter the ear canal, which is uncomfortable. The head shower is effective against headache; several studies support this observation [
411
-
414
]. You can use it more frequently than cold showers (up to once an hour) and the combination with pain medication is more effective against headache than either treatment alone. As a side note, there is some evidence that “natural diets” may be effective against recurrent headaches, as explained
at the end
of endnote X.

The modified cold shower procedure has similar beneficial effects compared to the adapted cold shower, without worsening a cough. Keep in mind that cold food and drinks as well as going outdoors in cold weather will worsen coughing.

Another useful trick during an upper respiratory tract infection is the washing the nasal cavity with saline. You can use a kit called “SinuCleanse.” This removes all the mucus that accumulates in the nose during this kind of illness and reduces discomfort. But first you need to decongest the nose. You can achieve this using a decongestant spray or by holding the breath. Exhale normally, pinch your nose, and hold your breath for 30 to 40 seconds or longer if you can. Then wait 2 or 3 minutes and repeat the procedure two or three more times. The breath-holding session can unblock the nose for 3 to 7 minutes. The mechanism of this effect of breath holding is unknown. Patients with anxiety disorders should be careful because this procedure can trigger a panic attack in this group of patients [
415
]. I did not invent breath holding; similar breathing exercises are a part of yoga. You can use nasal washing while the nose is unblocked. When pouring saline into your nostril, tilt your head back in order to fill the nasal cavity with saline completely. When blowing your nose after a nasal washing, do not strain too forcefully because this can cause discomfort or pain in the ears. Blow your nose gently out of both nostrils simultaneously to minimize pressure on the ear canal. Use moderately hot saline because heating will promote decongestion of the nose. The nasal cavity is a peculiar part of the body in that cooling causes dilation of the blood vessels (vasodilatation), whereas heating causes constriction of the blood vessels (vasoconstriction) in the nose. This is the opposite to what will happen to any other body part. After the head shower and after a cold shower that includes the head, nasal congestion may worsen temporarily—this should not be a cause for concern. If you take a cold shower
excluding
the head, this will reduce nasal congestion. I find head showers and adapted cold showers useful during respiratory infections, even though they can worsen nasal congestion temporarily. When the symptom of runny nose (rhinorrhea) is present, you can do nasal washings once or twice a day.

In conclusion, cold showers at 20°C (68°F) will not cause a respiratory illness. If you have a respiratory tract infection, you need to consult your doctor before using cold showers or any of the above treatments.

• A cooling procedure that does not lower
  normal
  core body temperature, such as a cold shower at 20°C (68°F), is usually safe and cannot cause a respiratory illness.
  
• On the other hand, transmission and survival of influenza virus increase in cold dry air. In addition, inhaling cold air inhibits immune defenses of the respiratory tract. These two observations can explain the predominant occurrence of respiratory infections in the winter.
  
• Eating ice-cold food and drinks for several days can cause a respiratory illness.
  
• When core body temperature is elevated (fever), cold hydrotherapy reduces it.
  
• Adapted cold showers at 20°C (68°F) work as a fever-reducing treatment; cold showers for the head (head showers) are effective against headache. Combining these methods with fever- and pain-reducing drugs such as aspirin or acetaminophen is more effective.
  
• Washing the nasal cavity with saline is effective against the symptom of runny nose.
  
• If a cough is present, you need to either avoid cold showers or modify them to exclude wetting the neck and chest areas.
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This section discusses the potential negative effects of cooling and heating in detail. The general advice is to avoid using either hot or cold showers daily, unless needed for occasional sleep problems. As they say, “don’t fix it if it ain’t broke.” (Readers can skip the detailed discussion of this topic and jump to the key points: press the skip button or
this link
.) My own experience suggests that each of these treatments can cause symptoms of hypomania when a healthy person uses them daily for many weeks or months. Daily use of hot showers can also cause physical health problems, including but not limited to back pain, muscle pain, skin irritation, and increased fatigue, based on my self-experimentation. On the other hand, once a week is fine and should not cause problems. If you feel nervous or depressed, you can use cold and hot showers, or the combination, as often as you like, up to 3 times a day. Don’t use adapted cold showers after 7 p.m. and if you use hot hydrotherapy
before
9 p.m., you need to follow it with an adapted cold shower, in order to prevent changes in your sleep pattern.

A recent publication reviewed negative effects of exposure to acute cold [
393
] (an open access article). The article concluded that a body cooling procedure should have few or no adverse effects on health if it does not involve hypothermia, psychological stress, and inhalation of cold air [
393
]. Winter swimming does not satisfy these criteria. Note that Raynaud’s syndrome, or excessive sensitivity to cold, is a contraindication for (moderate) cold water treatments [
416
].

1. Water colder than 14°C (56°F) can cause pain in the skin [
   417
   ,
   418
   ].
   
2. Exposure to acute cold for extended periods can cause a significant drop of core body temperature (hypothermia). This can have adverse effects on health, such as ataxia, hypovolemia, atrial dysrhythmias, and mental confusion [
   419
   ,
   420
   ]. Immersion in cold water in the range of 16 to 23°C (60 to 74°F) will not cause hypothermia (core body temperature of 35°C {95°F} or lower) in healthy human subjects [
   378
   ]. Hypothermia will not happen even if such immersion lasts for several hours. During this procedure, core body temperature stays virtually unchanged during the first hour [
   378
   ] due to the unusual efficiency of the human thermoregulatory system [
   421
   ]. Some elderly and people with certain metabolic disorders may develop hypothermia under these conditions; therefore, someone should monitor their body temperature if they use cold hydrotherapy [
   419
   ,
   420
   ].
   
3. The coldest months of the year show a higher incidence of acute heart failure and stroke (these problems are also more frequent during hot months) [
   422
   -
   424
   ]. In the experiment by Holloszy and Smith, where rats stood in cold water 4 hours per day, the incidence of cardiovascular problems increased according to postmortem examination. The average lifespan, however, also increased, by about 5%, and the incidence of tumors declined [
   395
   ]. It is not known whether daily
   brief
   exposure to moderately cold water (20°C, under 15 minutes), with gradual adaptation, has similar cardiovascular effects in the long term. Studies also show that sudden immersion in cold water can cause transient arrhythmias in some patients with heart problems [
   425
   -
   427
   ]. But short-term cardiovascular effects of cold water immersion are benign in normal test subjects [
   397
   ].
   
4. Swimming in ice-cold water can cause transient pulmonary edema (swelling of the lungs) in humans [
   401
   -
   403
   ], which may be due to severe hypothermia, among other things [
   420
   ].
   
5. Some studies show that sudden immersion in ice-cold water increases permeability of the blood-brain barrier in mice [
   428
   ,
   429
   ]. When repeated daily it can also increase mortality of neurovirulent infections (for example, West Nile virus, Sindbis virus). This is due to propagation of the infection to the brains of the mice [
   430
   ,
   431
   ]. The increased permeability of the blood-brain barrier in these studies can be due to the psychological stress associated with a dive into ice-cold water. This is because a different treatment that also causes distress to the animals, isolation, has similar adverse effects [
   429
   ]. In addition, immersion in ice-cold water rapidly causes severe hypothermia in mice [
   432
   ]. Hypothermia increases permeability of the blood-brain barrier in healthy animals [
   433
   ]. The proposed adapted cold shower procedure at 20°C (68°F) will not compromise the blood-brain barrier because it is not stressful (it contains a gradual adaptation phase) and is brief. Therefore, core body temperature will remain in the normal range.
   
6. If coughing is present, you need to avoid cold showers because they can sometimes worsen this symptom, according to my unpublished observations.
   
7. Because adapted cold showers promote wakefulness [
   343
   ,
   361
   ,
   362
   ], you shouldn’t use them at night or they may cause insomnia.
   
8. Because brief moderate cooling has psychostimulant effects, patients with bipolar disorder should be careful with adapted cold showers. Stimulant drugs can trigger mania in susceptible people (stimulant-induced mania). Bipolar patients should avoid cold showers during manic and hypomanic episodes. Personal experience suggests that if overactivity or elevated mood are present, adapted cold showers will further elevate activity and mood. (I have never had a diagnosis of bipolar disorder.)
   
9. Most contraindications of stimulant drugs may be applicable to adapted cold showers. In theory, this treatment may increase frequency of epileptic seizures in susceptible people, just like stimulants such as caffeine or amphetamine [
   87
   ].
   
10. Adapted cold showers can increase optimism and impulsivity. If you are trying
    not
    to make a rash decision, you need to avoid cold showers. Cold showers also seem to enhance anger and argumentativeness if these symptoms are present (whereas hot showers reduce these problems).
    
11. The list of contraindications is probably incomplete and readers who are taking medication or have a chronic medical condition need to consult with their physician regarding the safety of adapted cold showers.
    

According to numerous studies, moderate and brief cooling of the body is safe and does not have either short-term or long-term adverse effects on healthy subjects [
394
-
399
]. In the Holloszy and Smith experiment [
395
], scientists immersed rats in 23°C (74°F) water (up to the collar bone) for 4 hours 5 days a week. The experiment showed that the long-term repeated moderate cooling did not have visible negative effects on health. It extended the average lifespan of the rats by a statistically insignificant 5% compared to control rats [
395
]. According to another study [
394
], daily immersion in water at 20°C (68°F) for 1 hour for 5 weeks did not have adverse effects on healthy volunteers. On the other hand, the evidence presented above suggests that the practice of winter swimming (sudden immersion in ice-cold water) is unsafe and can have adverse health effects. Nonetheless, in a 4-month study of winter swimmers, who used this type of cold hydrotherapy 4 times a week, participants did not report adverse effects on health [
365
]. Adapted cold showers at 20°C (68°F) are safer and less stressful than swimming in ice-cold water and I recommend moderately cold showers instead of winter swimming.

Heat-based treatments are not appropriate for people who are taking the following medications or substances: alcohol, alpha-andrenergics, amphetamines, anticholinergics, antihistamines, benzodiazepines, beta-blockers, calcium channel blockers, cocaine, diuretics, laxatives, neuroleptics, phenothiazines, thyroid agonists, and tricyclic antidepressants [
654
,
655
].

Prolonged exposure to heat, for several hours to several days, can cause heat-related illnesses such as heat exhaustion and heat stroke.
Heat exhaustion
can happen at core body temperature between 37°C and 40°C (98.6°F to 104°F). It has the following symptoms: dizziness, confusion, headache, malaise or weakness, loss of appetite, nausea or vomiting, and vision disturbances.
Heat stroke
is a more serious condition. It can happen when core body temperature stays above 40°C (104°F) for several hours or longer. In addition to the above symptoms, heat stroke can result in a coma, seizures, loss of motor coordination, or internal organ failure.