Menstrual Cycle Influences Concussion Outcomes

How well a woman recovers from a concussion may depend on that time of the month.

Researchers found that women injured during the two weeks leading up to their period (the premenstrual phase) had a slower recovery and poorer health one month after injury compared to women injured during the two weeks directly after their period or women taking birth control pills.

The University of Rochester study was published today in the Journal of Head Trauma Rehabilitation. If confirmed in subsequent research, the findings could alter the treatment and prognosis of women who suffer head injuries from sports, falls, car accidents or combat.

Several recent studies have confirmed what women and their physicians anecdotally have known for years: Women experience greater cognitive decline, poorer reaction times, more headaches, extended periods of depression, longer hospital stays and delayed return-to-work compared to men following head injury. Such results are particularly pronounced in women of childbearing age; girls who have not started their period and post-menopausal women have outcomes similar to men.

Few studies have explored why such differences occur, but senior author Jeffrey J. Bazarian, M.D., M.P.H.says it stands to reason that sex hormones such as estrogen and progesterone, which are highest in women of childbearing age, may play a role.

"I don't think doctors consider menstrual history when evaluating a patient after a concussion, but maybe we should," noted Bazarian, associate professor of Emergency Medicine at the University of Rochester School of Medicine and Dentistry who treats patients and conducts research on traumatic brain injury and long-term outcomes among athletes. “By taking into account the stage of their cycle at the time of injury we could better identify patients who might need more aggressive monitoring or treatment. It would also allow us to counsel women that they’re more - or less - likely to feel poorly because of their menstrual phase.”

Although media coverage tends to focus on concussions in male professional athletes, studies suggest that women have a higher incidence of head injuries than men playing sports with similar rules, such as ice hockey, soccer and basketball. Bazarian estimates that 70 percent of the patients he treats in the URMC Sport Concussion Clinic are young women. He believes the number is so high because they often need more follow-up care. In his experience, soccer is the most common sport leading to head injuries in women, but lacrosse, field hockey, cheerleading, volleyball and basketball can lead to injuries as well.

Sex hormone levels often change after a head injury, as women who have suffered a concussion and subsequently missed one or more periods can attest. According to Kathleen M. Hoeger, M.D., M.P.H., study co-author and professor of Obstetrics and Gynecology at the University of Rochester School of Medicine and Dentistry, any stressful event, like a hit to the head, can shut down the pituitary gland in the brain, which is the body’s hormone generator. If the pituitary doesn't work, the level of estrogen and progesterone would drop quickly.