The study, published in the Archives of Internal Medicine, comes from Maurice Ohayon, MD, DSc, PhD, of Stanford University's medical school.
"Severe hot flashes are strongly associated with chronic insomnia in midlife women," writes Ohayon, who recommends asking women with chronic insomnia about hot flashes and possibly treating hot flashes to improve sleep quality.
About Hot Flashes
Hot flashes are a common symptom of menopause. Up to 85% of menopausal women experience them, according to background information cited in the study.
Data for Ohayon's findings came from 982 California women age 35-65 years. Ohayon split the women into three groups:
- Before menopause (premenopausal): 562 women
- Around the time of menopause (perimenopausal): 219 women
- After menopause (postmenopause): 201 women
Menopause doesn't happen overnight. Here's what those terms mean in this study:
- Premenopause: Women at least 35 years old who reported regular menstrual periods in the last year.
- Perimenopause: Women who reported irregular menstrual periods during the last year and had at least one period in the previous year.
- Postmenopause: Women who reported no menstrual bleeding during the last 12 months.
During telephone interviews, the women were asked if they had hot flashes. They also rated their hot flashes' severity by these standards:
- Mild: Hot flashes usually don't cause sweating.
- Moderate: Hot flashes usually include sweating that doesn't limit activities.
- Severe: Hot flashes usually cause sweating that prompts a woman to stop her activity.
Severity of Hot Flashes
Nearly a third of the women reported having at least three weekly hot flashes in the previous month. About 12% of the premenopausal group, 79% of the perimenopausal group, and 39% of the postmenopausal group reported having hot flashes that often.
Of the women with frequent hot flashes, about half experienced mild hot flashes and nearly one-third had moderate ones. But 15.5% said they suffered from severe hot flashes, Ohayon writes.
Like hot flashes, chronic insomniawas most commonly reported by perimenopausal women, followed by the postmenopausal women.
More than half of the perimenopausal women had chronic insomnia (nearly 57%). So did about half of the postmenopausal women (almost 51%).
Chronic insomnia was rarest among premenopausal women, the study shows.
Hot Flashes and Sleep
Many health problems can disrupt sleep. Ohayon took that into account.
Self-reported poor health, chronic pain, and sleep apnea(in which breathing stops temporarily during sleep) were tied to chronic insomnia. After considering those factors, Ohayon still found a strong link between severe hot flashes and chronic insomnia.
Of the 48 women who experienced severe hot flashes, about 80% had problems with chronic insomnia.
The women weren't followed over time. But more than half of the perimenopausal women and one in five postmenopausal women said their chronic insomnia began before, not during, menopause.
Even so, Ohayon found that "chronic pain and moderate or severe hot flashes were associated with chronic insomnia occurring around or after menopause."
"Treating hot flashes could improve sleep quality and minimize the deleterious consequences of chronic insomnia," Ohayon writes.
However, Ohayon's study didn't test any treatments for hot flashes.
The study was partly funded by NV Organon, which makes hormone therapies for menopause.