Vasomotor Hot Flushes

The hot flush is a sudden, transient sensation that ranges from warmth to intense heat, spreading over the face, scalp, and anterior thorax. It usually is accompanied by erythema and perspiration and is often followed by a chill. In some women, palpitations and anxiety accompany the flush. Each episode usually lasts from 30 seconds to several minutes, and the frequency and severity of flushes are quite variable.

Data have suggested that hot flushes occur in up to 75% of women.(44) Women who have undergone surgical menopause are more likely to have hot flushes than those with a natural menopause. Prevalence is highest in the first 2 postmenopausal years, and the episodes usually lessen with time. However, hot flushes may precede menopause by several years and may continue for 10, 20, or even more than 40 years after menopause.(10)

Severe hot flushes, which occur in roughly 15% of women, can disrupt a woman's life. Such episodes usually occur spontaneously, but are often increased in frequency or severity with hot, humid weather; confining spaces; or the ingestion of caffeine, alcohol, or spicy foods. Often, the flushes are increased by stress and tension, but they may be less frequent or less severe in obese women.

The precise etiology of the hot flush remains controversial, but it is associated with a drop in estrogen concentration.(10) The effects of estrogen go beyond the reproductive tissues to include thermoregulatory, neural, and vascular function. The firing rate of thermosensitive neurons in the preoptic area of the hypothalamus in response to thermal stimulation can be modified by estrogen.(10,45) Estrogen also influences internal body temperature.(10,46) The responsiveness of vascular smooth muscle to vasoreactive substances such as epinephrine and norepinephrine has been shown to be greater in women who have hot flushes than in those who do not.(47) Thus, estrogen probably has peripheral as well as central effects important in the physiology of the hot flush.

A primary problem caused by hot flushes is the disruption of sleep. Often, a woman is not only awakened from sleep, but also finds herself soaked with perspiration.(48) Although many women adapt by modifying diet and behavior, reducing room temperatures, and wearing light, layered clothing, 25% of women experience so much discomfort that they seek medical relief. Although available treatment does not "cure" them, it does provide symptomatic relief. The positive effects of estrogen therapy in this area have been documented for quite some time.(10) (Table 6) lists several nonpharmacologic actions that may help women establish more restful sleep patterns.(49)

Table 6