The main female hormone, estrogen, is hard to overestimate. And now we have even more evidence of this fact. Women with higher cumulative lifetime estrogen exposure have a lower risk of both ischemic stroke and intracerebral hemorrhage. These are the results of a new study published in the online issue of Neurology. It’s the medical journal of the American Academy of Neurology on February 1, 2023, ScienceDaily informs.
Ischemic stroke is caused by blockage of blood flow to the brain and is the most common type of stroke. Intracerebral hemorrhage occurs due to a ruptured blood vessel that leads to bleeding in the brain.
12.2 million people worldwide have their first stroke every year, and 6.5 million die from it. More than 110 million people in the world have experienced a stroke, and about half of them will die in the next 5 years. The incidence of stroke increases significantly with age, but more than 60% of strokes occur in people under the age of 70, and 16% in people under the age of 50.
Estrogen and stroke risk
A study by the Zhejiang University School of Medicine in Hangzhou, China, involved 122,939 postmenopausal women with an average age of 58. All of them lived in China and never had a stroke at the start of the study.
Participants answered questions about lifestyle and personal factors. Namely, age and occupation; their bad habits such as smoking and alcohol, data on physical activity and medical history. Plus, the researchers collected information on reproductive health. That included the age of first menstruation and menopause, the number of pregnancies and miscarriages, and the use of combined oral contraceptives (COCs).
The researchers analyzed health insurance and disease registry data to determine which participants had suffered a stroke. During the average follow-up period of nine years, 15,139 people had a stroke. Among them, 12,853 had an ischemic stroke, 2,580 had an intracerebral hemorrhage. Also, 269 had a subarachnoid hemorrhage, which is bleeding between the brain and the membrane that covers it.
The participants were divided into four groups according to the length of their reproductive life – the number of years from the first menstruation to menopause. Women with the shortest reproductive life span had up to 31 reproductive years. Those with the longest reproductive life span had 36 reproductive years or more.
When looking at different types of stroke, 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.
The researchers also looked at other factors that affect estrogen levels. These included the number of births and the use of COCs, based on the hypothesis that during these periods, estrogen has relatively higher sustained blood estrogen levels. The duration of breastfeeding, associated with lower estrogen levels, was also considered. Scientists have found that high concentrations of estrogen reduce the risk of all types of stroke.