- Stroke is an age-related disease due to hormonal and genetic factors but little is known about how reproductive experience influences risk.
- Epidemiological data suggest that sex-specific life experiences such as pregnancy increase stroke risk.
- Though pregnancy increases the risk of stroke, the recovery after stroke was better in mice which never reproduced.
Stroke is an age-related disease that disproportionately affects women. Although experimental studies have identified several hormonal and genetic factors underlying these differences, little is known about how pregnancy influences risk as this has not been previously studied in the laboratory setting.
However, new research published in the Proceedings of the National Academy of Sciences shows that while perimenopausal female mice that gave birth multiple times (multiparous) were at higher risk of stroke, they recovered better than mice that had not ever reproduced.
‘Female mice that had given birth multiple times demonstrated a surprising resistance to ischemic brain injury and improved behavioral recovery at chronic time points after stroke.’
Risk Factors of Stroke
Extensive clinical and statistical studies have identified several factors that increase the risk of stroke. Most of them can be controlled as they are the result of changing lifestyle and our consumption habits.
High blood pressure, cigarette smoking, physical inactivity, cardiovascular diseases, alcohol intake and a previous family history of stroke increases the risk in both men and women.
There are few risk factors which are unique to women. These include:-
Giving Birth Have Lasting Effects in Brain
- Use of hormonal contraceptives (birth control pills, birth control patch) slightly increases the risk of stroke.
- Risk of stroke increases in some pregnant women just before and after giving birth.
- The warning signs in these women are high blood pressure, protein in the urine, swelling of the hands and high blood sugar.
"Pregnancy and parturition have lasting effects on the brain and its response to injury," said Rodney Ritzel, PhD, a postdoctoral fellow at the University of Maryland School of Medicine and lead author of the study.
"Multiparity improves outcomes after cerebral ischemia in female mice despite features of increased metabovascular risk."
Multiparous mice, or females that have given birth more than once, typically exhibited many factors that put them at higher risk for stroke, the study found. This included increased body weight, elevated triglyceride and cholesterol levels, significant immune suppression, greater sedentary behavior and muscle fatigue.
While these attributes are generally associated with higher metabovascular risk, the female mice that had given birth multiple times demonstrated a surprising resistance to ischemic brain injury and improved behavioral recovery at chronic time points after stroke, the study found.
"Mice that were pregnant and had given birth had less brain inflammation, smaller brain injuries, and recovered better after stroke, despite showing signs of increased cardiovascular risk," Dr. Ritzel said.
The study examined the role of pregnancy and parturition on neurovascular function and behavior in both normal female mice and in females exposed to stroke. The research found that reproductive experience increases systemic metabolic risk and results in significant behavioral deficits that are associated with central nervous system immunosuppression
After stroke, however, multiparous females exhibited smaller infarct volumes, attenuated inflammatory responses, enhanced angiogenesis, and improved behavioral recovery.
Ritzel added that this study provides valuable insight into stroke recovery in women. He highlighted the importance of modeling the differences between child-bearing and non-child-bearing women when researching the impact of strokes and other brain injury.
- Rodney M. Ritzel et al., Multiparity improves outcomes after cerebral ischemia in female mice despite features of increased metabovascular risk, Proceedings of the National Academy of Sciences (2017)