A group of older men and women laugh while standing on a small boatShare on Pinterest
Researchers say lifelong exposure to estrogen can reduce the risk of stroke. Halfpoint Images/Getty Images
  • A new study reports that people who have a long lifetime exposure to estrogen have a lower risk of stroke.
  • Ischemic stroke is caused by blood clots that block blood vessels in the brain and researchers say estrogen can help widen the blood vessels.
  • There are numerous factors that affect estrogen levels, including age, genetics, and environmental and lifestyle factors.

Estrogen therapy and its impact on stroke risk remains a much-debated topic.

While too much estrogen can cause reproductive issues, past research indicates that the risk of cardiac and stroke death increases in the first year after stopping hormone therapy.

Experts say this suggests the crucial role hormones play in heart health.

According to a new study, published today in the journal Neurology, people with longer exposure to estrogen may have a lower risk of stroke, which includes both ischemic stroke and intracerebral hemorrhage.

An ischemic stroke occurs when blood flow to the brain is blocked. An intracerebral hemorrhage, on the other hand, is caused by the rupture of a blood vessel in the brain, which leads to internal bleeding.

For the study, researchers examined nearly 123,000 postmenopausal female participants without a previous history of stroke, collecting data on medical history, lifestyle, and reproductive health information.

The participants were separated into four groups based on their reproductive life span and the number of years from their first period to menopause.

The researchers reported that the female participants with the longest reproductive life span had a 5% lower risk of ischemic stroke and a 13% lower risk of intracerebral hemorrhage compared to women with the shortest reproductive life span.

“Our study suggests that higher estrogen levels due to a number of reproductive factors, including a longer reproductive life span and using hormone therapy or contraceptives, are linked to a lower risk of ischemic stroke and intracerebral hemorrhage,” said Peige Song, Ph.D., a study author and researcher at the Zhejiang University School of Medicine in Hangzhou, China, in a news release. “These findings might help with new ideas for stroke prevention, such as considering screenings for people who have a short lifetime exposure to estrogen.”

Dr. Atif Zafar, the chief of the stroke program at St. Michael’s Hospital of the University of Toronto, said that although more research is needed, there does appear to be a connection.

“The long reproductive lifespan reduces the risk of stroke in women likely due to the cardioprotective benefits of endogenous estrogen hormone,” Zafar told Healthline. “I am using the word endogenous as we do not want people to start supplementing themselves with estrogen until there is more research in the area.”

“Although more research is being done in this area,” he added. “I personally believe there is something in the natural (endogenous) estrogen (probably along with progesterone) that provides protection against stroke.”

“Estrogen has been shown to cause vasodilation, which is the widening of blood vessels, by boosting the synthesis and secretion of nitric oxide and prostacyclin in endothelial cells,” said Dr. Alex Polyakov, an associate professor and gynecologist at the University of Melbourne in Australia.

“It also relaxes the smooth muscle cells in blood vessels by activating specific calcium channels,” he told Healthline.

He added that the new study suggests that higher lifetime exposure to estrogen may have a protective effect against intracerebral hemorrhage, a type of stroke caused by the presence of a hematoma in the brain.

Polyakov said estrogen has been shown to have neuroprotective effects and to have antioxidant properties, which may help to reduce neuronal damage.

“The reason why those who started menstruation early and went through menopause later had a lower risk of stroke may be because longer exposure to estrogen can provide a protective effect against stroke,” added Dr. Adil Maqbool, an expert in nutritional and metabolic diseases at Allama Iqbal Medical College in Pakistan.

Maqbool told Healthline that estrogen has been shown to have anti-inflammatory and vasoprotective effects, which could contribute to a reduced risk of stroke.

The study does not specifically address the relationship between birth control use and stroke risk.

“Birth control, particularly hormonal birth control, involves a different kind of exposure to estrogen and other hormones,” Polyakov said. “In general, hormonal birth control methods increase the levels of hormones like estrogen in the body, and some studies have suggested that there may be a link between hormonal birth control use and an increased risk of stroke, although the evidence in this area is not conclusive.”

Further research is needed to understand the exact relationship between estrogen, birth control, and stroke risk.

“Past studies have shown that estrogen may have a protective effect against cardiovascular disease and stroke,” added Maqbool. “However, it’s important to note that oral contraceptives, which contain synthetic forms of estrogen, have been associated with an increased risk of stroke in some cases.”

Estrogen levels can be affected by a number of factors, according to Polyakov.

These include:

Age: Estrogen levels naturally decline as women approach menopause.

Hormonal birth control: The use of hormonal birth control, such as the pill or IUD, can alter a woman’s estrogen levels.

Pregnancy: During pregnancy, estrogen levels increase.

Body weight: Obesity can affect estrogen levels, as body fat can produce and store estrogen.

Genetics: Genetics can also play a role in determining estrogen levels.

Environmental factors: Exposure to endocrine-disrupting chemicals, such as phthalates, can impact estrogen levels.

Lifestyle factors: Alcohol consumption and smoking can also affect estrogen levels.

“It’s important to note that while these factors can influence estrogen levels, they may not necessarily impact the risk of stroke, which is determined by a complex interplay of genetic, lifestyle, and environmental factors,” Polyakov added.