Hormone replacement therapy during and after menopause is utilized by millions of women across the country. While it’s well known there may be side effects to the therapy, a recent study has found that worsening migraines may indicate an increased risk of stroke.

Menopause is a natural part of aging for women. It’s when levels of female hormones go up and down, causing a range of undesirable symptoms such as hot flashes. Women take hormone replacement therapy (HRT) to lessen these symptoms. But the treatment comes with its own risks depending on the woman’s lifestyle and history, including a heightened risk of breast cancer, heart disease, and stroke. According to researchers, women using HRT who reported severe migraines were 30 percent more likely to have an ischemic stroke than women who used it in the past or never did.

“Many postmenopausal women use hormone replacement therapy, and a large number also experience migraines, although we’re not sure if these put them at a greater risk of stroke,” said lead author Dr. Haseeb A. Rahman, a neurology resident at Houston Methodist Hospital in Texas, in a press release. “The question we wanted to address was whether there is greater risk of stroke if migraines are becoming more severe while taking hormone replacement.”

Rahman explained past studies had looked at stroke risk factors, but each came to different conclusions, leaving “gray areas” of understanding. He said his study is the first to his knowledge to look at a change in migraine severity with HRT as a risk factor for ischemic stroke.

The study used the medical data of 82,208 women aged 50 to 79 years old from the Health Initiative Study, which began in the 1990s. All of the women reported some degree of migraines when they enrolled in the study, and about 45 percent were using HRT. At a follow-up visit three years later, the women were asked if their migraines had gotten better or worse. And then after 12 years, 2,063 had suffered an ischemic stroke during the study.

After adjusting for common risk-factors including age, high blood pressure, high cholesterol, diabetes, and smoking, the researchers determined those women whose migraines had gotten worse during HRT had a higher risk of stroke. Rahman said the results indicate women with a history of migraines should pay close attention to the risks and benefits of HRT, and if they choose to begin the treatment, they should monitor the severity of their migraines.

“You should not simply ignore an increasingly bad migraine,” Rahman said. “You should also tell your doctor if you’re getting migraines for the first time while on hormone replacement therapy.”

Women should work with their doctors to identify all of their risk factors for stroke, especially if they’re on hormone replacement. Rahman said they can create a plan “to improve and address these factors as best they can.”

Source: Rahman H, Malik A, Saeed O, Thomas A, Quereshi A. Worsening migraines with hormone replacement linked to stroke risk. International Stroke Conference 2016. 2016.