Women’s body temperature rises from age 18 to 42 but we don’t know why
Hot flashes are associated with menopause, but women become progressively hotter from early adulthood through their 40s.
Dmitry Marchenko/Alamy
Resting body temperature increases slightly each year in women aged 18 to 42, for reasons that remain to be understood. This discovery opens the possibility of using temperature-sensitive wearable devices to track aging and detect perimenopause or potential health problems.
“We think the temperature signal contains a lot of information about health,” says Marie Gombert-Labedens of SRI International, a research institute headquartered in California. “We hope this will facilitate investigations to identify new disease markers – it could provide an untapped resource of information about our health.” »
Gombert-Labedens and colleagues analyzed data from a 1990s study that asked more than 750 women aged 18 to 42 to measure their oral or rectal temperature with a thermometer every day when they first woke up.
The results showed that, on average, body temperature was lower during the first half of participants’ menstrual cycles and higher during the second half, after ovulation. Many fertility tracking apps use this temperature jump to predict a user’s fertile window.
Gombert-Labedens and colleagues re-examined the data in more detail to study the effect of age on temperature at different stages of the menstrual cycle. They found that each year, between the ages of 18 and 42, participants on average became a little hotter. As a result, people aged 35 and over recorded a temperature approximately 0.05°C higher than younger subjects during both halves of the menstrual cycle.
This is consistent with the team’s previous research which found that finger skin temperature, measured continuously by a smart ring, was on average warmer in women aged 42 to 55 than in those aged 18 to 35.
More research is needed to explain why this increase in temperature occurs, but it likely has something to do with hormonal changes, particularly toward the end of the breeding years, says Gombert-Labedens. When perimenopause begins, the temperature can rise suddenly and cause hot flashes and night sweats, but it’s unclear whether this is related to the same mechanisms, she says.
The study only included women who were not using hormonal contraception and did not have hormonal disorders such as PMS (polyendocrine ovarian metabolic syndrome, formerly known as PCOS). So we don’t yet know how these factors might affect body temperature over time.
Other research has shown that after menopause, women’s body temperatures tend to drop to a lower level and become similar to men’s.
The higher temperature around midlife may explain why, anecdotally, some women this age say they don’t feel the cold as much as they used to, says Gombert-Labedens. “We think that the higher temperature in middle-aged women could influence their perception and reaction to ambient temperature,” she says.
As smart rings and other wearable temperature-sensing devices become more popular, it may be possible to identify patterns or deviations in individuals’ temperature trends that signal approaching menopause, provide an estimate of their biological aging rate, or detect early signs of ovarian cancer or other conditions, says Gombert-Labedens.
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