People with higher cumulative estrogen exposure over their lifetime may have a lower risk of stroke, according to a new study published February 1, 2023 in the online edition of neurology®, the medical journal of the American Academy of Neurology. The lower risk was found for both ischemic stroke and intracerebral hemorrhage.
An ischemic stroke is caused by a blockage in blood flow to the brain and is the most common type of stroke. An intracerebral hemorrhage is caused by bleeding in the brain.
“Our study suggests that higher estrogen levels are associated with a lower risk of ischemic stroke and intracerebral hemorrhage due to a number of reproductive factors, including longer reproductive lifespan and use of hormone therapy or contraception,” said study author Peige Song, PhD, from the Zhejiang University School of Medicine in Hangzhou, China. “These results could help with new ideas for stroke prevention, such as
The study enrolled 122,939 postmenopausal female participants with an average age of 58 years who lived in China without a stroke at the start of the study.
Participants answered questions about personal factors such as age, gender, and occupation, as well as lifestyle factors such as smoking, alcohol consumption, exercise, and medical history. They also answered questions about reproductive health information, including age at first menses and at onset of menopause, number of pregnancies and miscarriages, and use of oral contraceptives.
Researchers looked at health insurance and disease registry data to determine which participants had a stroke. During a median follow-up of nine years, 15,139 suffered a stroke. Of these, 12,853 had an ischemic stroke, 2,580 an intracerebral hemorrhage, and 269 a subarachnoid hemorrhage, which bleeds between the brain and the membrane surrounding it.
Participants were divided into four groups based on their reproductive lifespan, the number of years from the first menstrual period to menopause. Participants in the group with the shortest reproductive life span had up to 31 reproductive years. Participants in the group with the longest reproductive life span had 36 reproductive years or more.
As a percentage, participants in the longest group had slightly more strokes than those in the shortest group, 13.2% versus 12.6%. However, when the researchers considered other factors that might affect stroke risk, such as age, smoking, physical activity and high blood pressure, they found that participants in the longest group had a 5% reduced risk of all types of stroke.
Looking at different types of stroke, participants with the longest reproductive lifespan had a 5% reduced risk of ischemic stroke and a 13% reduced risk of intracerebral hemorrhage compared to women with the shortest reproductive lifespan.
The researchers also looked at other factors that affect estrogen levels, such as number of births and oral contraceptive use, both of which are associated with higher levels, and length of breastfeeding, which is associated with lower levels, based on the hypothesis that Pregnancy and oral contraceptive use represent relatively higher sustained levels of estrogen in the blood. They found that higher levels of estrogen resulted in a lower risk of all types of stroke, as well as ischemic stroke and intracerebral hemorrhage.
“Lifetime estrogen exposure could potentially be a useful predictor of a person’s risk of having different types of stroke after menopause,” Song said. “However, more research is needed on the biological, behavioral, and social factors that may contribute to the association between estrogen exposure and stroke risk across a woman’s lifespan.”
A limitation of the study was that reproductive factor information was collected primarily based on participants’ ability to recall events, and participants may not have correctly recalled such events.