The authors surveyed 128 girls and women aged 12 to 21 who had either a head injury or an orthopedic injury from athletic or recreational activity within the 30 days before the study started. Nearly a quarter of the 68 girls who had concussions -- 23.5% -- experienced two or more abnormal bleeding patterns in the 120 days after their injuries, while only 5% of the 60 girls without concussions had the same irregularity.
The irregular periods are caused by the disruption of the neuroendocrine hypothalamic-pituitary-ovarian axis, which can occur from concussion, according to the study. This refers to the part of the brain that helps develop and regulate the body's reproductive and immune systems.
Anthony P. Kontos, research director at the University of Pittsburgh Medical Center Sports Medicine Concussion Program and a co-author of the study, said the idea was formulated when Dr. Meredith Snook, an OB-GYN fellow, approached him. She wanted to take a look at menstrual cycle patterns and potential irregularities after concussion.
When they began to examine existing research, they found that almost all studies on concussions had to do with the relation to traumatic brain injuries, but some of the literature suggested that brain injury could disrupt menstrual function, Kontos said.
They decided to focus on a younger group of girls because they were more interested in seeing whether a disrupted menstrual cycle could have any negative consequences later in life, he said. The participants were told to send text message updates regarding their periods.
"We did not know if the participants would even provide us with this information because it was somewhat sensitive," he said. "We just didn't know if they would respond, and we had a 95% response rate, which was off-the-charts ridiculous, so clearly they were interested."
The study did not control for at what point participants were in their sporting seasons. Female athletes who perform intense exercise are more prone to menstrual irregularities, said Dr. Dennis Cardone, co-director of the Concussion Center at NYU Langone Medical Center and an associate professor in the Department of Orthopaedic Surgery.
"They didn't control for that, and that's key," said Cardone, who was not involved in the study. "If you took a female population in the beginning of their sporting season compared to middle or end, in an intense strenuous sport, then the likelihood is that a decent amount probably are going to have menstrual irregularities, just related to the strenuous exercise that they're doing. So the timing really would make a big difference here.
"I think that this is a good awakening study in the sense that I don't think, for many of us, this was near the top of our list for things we should be paying attention to in our female athletes who sustain a concussion."
A 2015 study
found that for every 10,000 times a student athlete participated in a soccer game or practice, there were 4.5 concussions among girls and 2.8 among boys. Other research has showed
that female concussed athletes report more concussion symptoms than males.
Cardone said it was possible that the study could give insight into why women report more severe concussion symptoms.
"It could add to it, right? It's the chicken and the egg thing, like which comes first in some sense. Is it the concussion or the hormonal irregularity exacerbating the effect of the concussion?" he said. "So maybe this really does play some role in recovery."