The cause is uncertain but the effect is known only too well to millions of women – a rise in skin temperature of 4 to 6 degrees C, a marked increase in heart rate, palpitations, and a reflex opening of the blood vessels to reduce body temperature, giving the skin a flushed appearance. These symptoms tend to clear after a few minutes and may be followed by a feeling of coldness that can lead to shivering.
Hot flushes are likely to peak in the first months to years after the last menstrual bleed, although they also occur in many women who are menstruating regularly. In either case, they provide a good deal of embarrassment and discomfort.
The rate of hot flushes in the non-menopausal female population is about 10 to 20 per cent. For most women the rate of flushes declines rapidly after menopause, although about 10 per cent are still having flushes ten years later, rather longer than most women would like.
We do know that hot flushes parallel an increased output of luteinising hormone produced in a region of the brain that is close to the body’s heat centre. There also seems to be a link between flushes and changes to the normal working of blood vessels. One theory links low oestrogen levels with an increase in brain chemicals, leading in turn to a change in the temperature monitoring and regulating part of the brain. This is said to result in the experience of a hot flush, with its associated increase in pulse rate and blood flow to the skin.
Another thing that seems to affect the timing and severity of flushes is anxiety. It is sometimes possible to find connections between anxious situations and the onset of a flush. Stress, the vague state of tension that so much ill health is now put down to, can also increase the tendency to flush. Things that can trigger stress reactions include sleep deprivation, a hot and stuffy environment, thyroid disease and alcohol -common enough factors in anyone’s life.