"Doctor, just what is a hot flash?"

Hot flashes, hot flushes, power surges-- they go by a variety of names and are one of the most common symptoms of the perimenopause and menopause. Often a premenopausal woman will ask, "how will I know if I am having hot flashes"? This can be compared to the question a woman who has never had a baby asks, "how I will know if it's really a contraction"? If a woman is having significant hot flashes, she will not have to ask! Hot flashes will often appear intermittently long before the menses stop, but then become more intense and frequent during the transition through the menopausal period. The timing of this increase in severity is variable and the increase may appear either before or after the cessation of the menses.

Many aspects of hot flashes are still not completely understood. Over 80% of North American women have them at some time in their lives, and hot flashes most commonly last for a few months up to a couple of years. However, 25 to 50 % of women will have them for over five years, and an occasionally unfortunate woman may have them into her seventies or eighties! On the other hand, a few women never experience them at all. Interestingly, the frequency of hot flashes varies from culture to culture; for instance, Japanese women do not seem to get them as often as American women. However, as with most things in menopause, the frequency as well as the severity is variable. Certainly hot flashes may have a profound effect on a woman's life, and may be devastating when they are frequent and intense.

Hot flashes are described as a feeling or wave of heat that often seems to engulf the upper torso and head. It is a feeling of intense warmth that may spread like a wave over the upper body, and typically lasts from 30 seconds to 3 or 4 minutes. This wave is followed by a visible flushing of the skin, and after this flush the woman will notice profuse sweating over this part of her body. Usually she is turning down the heat (or the air conditioning up) while everyone else around her is comfortable. (And of course this always gives rise to the frequent and repetitive jokes about whether she has taken her hormones that day).

Hot flashes are caused by a phenomenon called vasomotor instability. To understand this phenomenon first one must understand some basic physiology about the body. Blood vessels in the skin of the body can dilate or constrict (open up or narrow down), depending on what the body tells them to do. If the body gets hot, then it sends blood to the outside of the body by dilating or opening the blood vessels in the skin. This allows the heat of the blood, and thus of the body, to dissipate or leave and cool the body down. This is just like in an automobile when the water runs through a radiator to cool the car down. This ability of the body to cool itself is a regulatory mechanism for heat control of the body, and a thermoregulator in the brain directs this regulation. One may think of this as the body's thermostat. The thermoregulator in a woman's brain controls the body's heat and cooling regulatory function, just as the thermostat in a house controls the heater and air conditioner.

If the thermostat on a house is constantly changed, or someone is frequently moving it up and down, then the air conditioner of the house will be constantly be going on and off. This is similar to what happens in a woman having hot flashes; the thermostat in her brain is bouncing up and down. All of a sudden it tells the body it is hot, and tells the body to send all of the blood to the skin to cool the body down. First the woman feels hot as her thermostat has told her she is hot. Next the blood is sent to her skin and the flush or redness appears. Then the sweating begins as her body tries to cool itself off. Then, after only a few minutes, the thermostat resets itself and the woman feels normal again, but only later to undergo the same cycle again.

While many things such as diet, caffeine, heat and stress are known to trigger hot flashes, the underlying cause is known to be a decrease of estrogen in the body. While the general mechanisms of the hot flash can be explained, the reason why less estrogen causes this instability of the body's thermostat is less certain. And, the more rapid the drop of estrogen, the more severe the hot flashes tend to be. A very slow transition into menopause often is associated with less problems than that of a more rapid one, such as may be seen with surgery and removal of the ovaries. So, while we know what is going on, we do not know exactly why it is going on; which is of little comfort when a woman is plagued with severe symptoms.

It is also thought that hot flashes that occur during the night cause many of the problems with sleep disturbance. The hot flash may not entirely wake a woman up, but causes enough of a disturbance in her body to interrupt the restful part of her sleep. It is like someone is gently but repeatedly shaking her throughout the night, just enough to nearly but not quite awaken her! When this occurs over and over throughout the night, then no wonder she gets up still feeling tired. She feels exhausted and fatigued during the day, and cannot understand it because she "sleeps" a normal amount of hours during the night. Unfortunately, it is not a restful or continuous sleep, being broken up by hot flashes without the woman knowing or entirely waking up. This situation probably also contributes to the increased irritability that a women will note during the menopausal and perimenopausal years. Certainly if a woman does not rest well at night, then she does not feel good during the rest of the day.

As for treatment of the hot flashes, there are numerous approaches to resolving or working with them. Replacement of estrogen is generally recognized as the most effective way to stop them, a treatment that certainly makes sense as hot flashes seem to be caused by a drop in a woman's estrogen. Other hormones such as progesterone may also help to alleviate them, and in addition there are many homeopathic remedies and substances that may provide some relief. Often life style changes consisting of such things as increased exercise and dietary changes are recommended and may help. Other approaches such as biofeedback and stress reduction techniques have been shown to provide some decrease in the frequency and intensity. The overall approach to the treatment of hot flashes is beyond the scope of this article, but there are many approaches to working and dealing with them, depending both on the severity of the hot flashes as well as a woman's preferences in managing these symptoms in this phase of her life.