Hot flushes: where they come from, how long they last and what you can measure yourself

In this article you will read where hot flushes come from, how long they last and what you can measure yourself. That matters, because once you know what is happening, you can choose better what you do about it. It starts in your chest or your neck, moves up to your face in a few seconds, and then you are sweating while everyone around you simply sits there. At night it wakes you up and the duvet ends up on the floor. Hot flushes are the best known complaint of the menopause, and still most women do not know where they come from, how long they last or what they can measure themselves. The BioProfile hormone scan measures how much trouble these complaints give you, and gives you an indication of where you stand today in this area, the first of the 11 health areas the full scan assesses. This is not a diagnosis. It is insight, to see where you stand today. And to help you make better choices in your food and your lifestyle. What this scan does not do: measure a hormone or make a diagnosis. Only a doctor can do that.

What a hot flush is

You suddenly feel very warm, you go red, you sweat and sometimes your heart pounds. A hot flush usually lasts 3 to 5 minutes, sometimes longer, and most women going through the menopause have them, from a few a month to a few an hour.⁠³

What happens then is a cooling response far too large for what set it off. Normally your body has a window in which a small swing in core temperature starts nothing at all: only above the upper limit do you begin to sweat, only below the lower limit do you begin to shiver. During the menopause that window narrows, partly because oestrogen falls away and partly because of higher activity in the part of your nervous system that puts your body on alert. A small rise in core temperature then reaches the upper limit straight away, and your body answers with heavy sweating and the blood flow to your skin thrown wide open, as if you were overheated.⁠¹

How long hot flushes last

Thuisarts puts it at usually 3 to 7 years.⁠³ The two large cohorts that followed women for years came out higher. In the American SWAN study, 1,449 of the 3,302 women followed had frequent hot flushes or night sweats; for them the median duration of those complaints was 7.4 years, for more than half of them longer than seven years, and in the 881 of them whose last period was established during the study, the complaints carried on for a median of 4.5 years after that. Those who began early, before or at the start of the menopause, came out at a median above 11.8 years; those who only began after the last period, at 3.4 years.⁠⁴ A second cohort, followed for thirteen years, came out at a median of 10.2 years for moderate to severe hot flushes, with the start most often between the ages of 45 and 49.⁠²

What goes together with more hot flushes

In 3,198 women who were followed for six years, the stage was linked most strongly with hot flushes: in the late transition the chance was more than six times as high as before that. Smoking, a higher weight and anxiety symptoms at the start of the study were also linked with more frequent hot flushes.⁠⁵ That is an association, not a cause, but these are the things that belong on the table in a conversation with a doctor.

Thuisarts also names what can set off a hot flush: alcohol, above all when it comes to sweating at night, hot drinks and spicy food.⁠³

Hot flushes and sleep

Many hot flushes at night coincide with a measurable awakening, and the time you then lie awake counts for a good deal of the total restlessness of the night; 26 per cent of women going through the menopause have sleep problems bad enough to get in the way during the day.⁠⁶

What stands out is which hot flushes do that. In 52 women who were measured at home for four full days and nights, with a skin sensor for the hot flushes and a wrist monitor for sleep, the hot flushes they remembered in the morning were linked with worse sleep: less efficient and with more time awake. The hot flushes the sensor recorded but that they had not noticed barely did so.⁠⁷ So what you notice yourself is exactly what counts for your day, and that is exactly what a questionnaire records.

What a hormone scan measures

The hormone scan starts with your stage of life. Women in or around the menopause get four questions about the past few weeks, and the first one is about hot flushes or night sweats; the other three about vaginal dryness, irritability or mood swings, and sleep that is disturbed by hormonal changes. Each question is given points, the points are converted into a hormone score from 0 to 100, with the reading band it falls into. Higher is better.

The questions are modelled on the Menopause Rating Scale, a questionnaire of eleven questions in three groups, physical, psychological and urogenital, which has been tested in nine countries and turned out to measure the same thing everywhere.⁠⁸ Our four questions follow that construct in our own words, are not a copy of it, and so the score is not a validated clinical score.

What a hormone scan does not measure

Complaints, never hormones. The scan says nothing about your oestrogen, your testosterone or your thyroid; only a blood test sees a hormone, and pronounced complaints are the reason to ask for one. A hormone scan does not make a diagnosis. Four things are a reason to make an appointment with your GP: very heavy bleeding, complaints before the age of forty, bleeding more than a year after your last period, and a lot of trouble from hot flushes.⁠⁹

What you do with your score

A score from today is your baseline. Repeat the scan in a few weeks, over the same questions, and you have two numbers instead of a feeling about a stage that lasts years. If you want to try something in those weeks, pick something from the Thuisarts list and keep track of what you notice: the hot flushes you remember are the hot flushes that cost you sleep.⁠⁷