In many cultures throughout history and even today, the methods of bathing are different from ours. Some of the rituals would seem quite strange to those of us that have a shower and bathtub in our own homes or apartments. But as we travel, we become aware of other cultures and developments that at first seem odd, but later seem to invade our society. One of the more prevalent customs that has made it to the US is the use of the hot tub or Jacuzzi.
One of my classmates made a commercial for hot tubs. I am not sure that it is a good idea for doctors to be making commercials; on the other hand, it is a doctor's responsibility in taking the lead and teaching consumers about health. In Japan it is quite common to use shared public baths that in fact are hot tubs. In that country, soaping and washing takes place before entry into the tub. In other countries, the practice of a dry hot sauna followed by a cold shower may be more common. The concept of a shared bath is often strange to people born in the US, but in some areas of the globe it is a communal and culturally different experience brought on initially by the lack of running water in most houses or villages.
From the medical point of view, the shared bath has been claimed by some to have therapeutic value based on water content in some cases due to radioactivity, in others due to dissolved minerals, and by others to be a source of spread of infections. What has been the source of some interest from the cardiology point of view is the possibility that the use of hot tub or sauna might be dangerous for the patient with any type of heart disease. In this litigious country (we have more lawyers per population than any other country in the world) it is quite common to see signs at any public Jacuzzi, hot tub, or sauna suggesting that people should not enter if they have high blood pressure, heart disease, or pacemakers, and should discuss use with their physician. I have been requested to provide a doctor's note on one occasion. What is the basis for this warning, and have their been true scientific studies that relate to this subject?
Initially, after immersion in hot dry air or water Jacuzzi, hot tub, hot bath), the blood vessels closest to the skin will dilate causing a drop in blood pressure. This is accompanied by constriction of the splanchic vessels (and thus less flow to the gut, slowing digestion). It was presumed that this constriction of the splanchnic vessels could include the vessels to the heart and the brain therefore increasing the possibility of heart attack (no evidence for this). It has also been suggested that the drop in blood pressure, or changes in heart rate due to the dilation of the skin or "resistance vessels" would be too much for patients to tolerate in certain cardiac conditions. These suggestions are not based upon any scientific observations. In fact, several properly accomplished studies have demonstrated that a 10-minute hot-tub immersion in patients with treated hypertension is safe. Of course blood pressure does go down while in the tub, and for some time afterward, but isn't that the goal of treatment of high blood pressure?
There is also no evidence that immersion in such a bath is dangerous for people that chronically have lower blood pressures.
Interestingly, the observation that blood pressure can be lowered by hot tub immersion, and an old observation that excess water can be effectively driven from the body by the diuretic effect of what was called many years ago "head out water immersion," has led to the thought that this could be used as a treatment of patients with congestive heart failure. Recent scientific studies on the use of hot tubs in patients with congestive heart failure have demonstrated clinical benefits. No studies or observations have suggested danger to pacemaker patients in the use of hot tubs.
It is important to note that all hot tub studies in "cardiac patients" have been limited to 10-minute exposures (at 106 degrees Fahrenheit) and have been done in safe conditions. Neither scalding water nor blistering heat is beneficial for anyone. Slippery surfaces still cause more accidents then cardiac or infectious problems in the sauna, whirlpool, Jacuzzi or hot tub. As always, please consult your physician.