Hot flashes can result in forgetfulness among women approaching menopause, says a new study by US researchers.
The study, which found that women in midlife underreport the number of hot flashes - the uncomfortable symptoms of menopause -they experience by more than 40 percent, is the first to explore the relationship between objectively measured hot flashes and memory performance.
Memory complaints are common at midlife, and previous research indicates that about 40 percent of midlife women report forgetfulness.
"The problem is that the physiology of hot flashes and the science of hot flashes is more complex than we previously understood," said the study's author.
In the research, 29 midlife women with moderate to severe hot flashes were enrolled in an observational study.
The women wore monitors that measured changes in skin conductance during a hot flash. Both subjective and objective hot flashes were recorded during a 24-hour period. The average number of objective hot flashes was 19.5 per day.
The research team also objectively measured memory performance - the recollection of words, names, word pairs, paragraphs and stories - using standard neuropsychological tests.
"When we looked at the relationship between the hot flashes that the women truly had - that is, the hot flashes that the monitor picked up - and memory performance on the cognitive tests, we found a very strong relationship. So, the more true hot flashes a woman had, the worse her memory performance," the researcher said.
The researcher added: "In other words, the hot flash-memory relationship is not all in a woman's head. It's actually a physiological relationship that you can pick up on, if you measure hot flashes objectively with a monitor."
When the researchers looked at the relationship between hot flashes women thought they had - their subjective hot flashes - there was no relationship with memory performance.
The team also observed a relationship between the total number of hours slept and memory performance the next day.
"The total number of hours slept predicted worse memory performance, but also the total number of hot flashes during the night when a woman was sleeping predicted memory dysfunction. So, the two together worsen memory in women the next day," the researcher said.
The study suggests that if women are treated for their vasomotor symptoms it may improve memory function in women with hot flashes.
The study is published is published online and will appear in the September/October issue of the journal Menopause.