Understanding Gender Differences in Chronic Pain

Researchers examining chronic pain have long been intrigued by a puzzling scenario: a man and a woman might suffer identical injuries in a car accident, yet the woman often grapples with lingering pain while the man recovers quicker.

In the past, some medical professionals have shrugged off these disparities, attributing them to claims of exaggeration among women or suggesting they handle discomfort differently than men. However, numerous studies have shown that women are generally more prone to chronic pain and tend to endure pain for longer periods.

A recent study published in Science Immunology sheds light on this issue, suggesting that men’s immune systems may be more efficient at managing pain, perhaps due to higher testosterone levels.

Geoffroy Laumet, an associate professor at Michigan State University and a co-author of the study, emphasized, “What we show is a tangible biological mechanism from the immune cells. It’s not just psychological.”

Ann Gregus, an assistant professor at Virginia Tech who investigates chronic pain treatments, pointed out that the findings highlight the importance of acknowledging women’s pain seriously.

“Many women are often encouraged to suppress their pain, as not doing so might lead others to think they are incapable of fulfilling responsibilities,” Gregus, who wasn’t part of the study, remarked.

The research primarily relates to pain that persists after surgery or physical trauma, but other chronic pain conditions, such as fibromyalgia, arise without any previous traumatic event.

“Does this explain everything? I wouldn’t say so. We don’t have a singular solution,” noted Dr. Michele Curatolo, a professor specializing in anesthesiology and pain medicine at the University of Washington, who was not involved in the current research. She now serves as the chief medical officer at 4E Therapeutics, a company focused on neuroscience and pain treatments.

In their study, researchers asked 245 participants who had suffered traumatic injuries—mostly from car accidents—to evaluate their pain levels. Although both men and women reported similar severity on the day of the injury, men showed quicker pain resolution over a three-month follow-up.

Blood analysis revealed that men exhibited higher levels of a molecule known as interleukin-10, which helps reduce pain signals sent to the brain. Laumet attributed this increased production of interleukin-10 to testosterone’s effects on white blood cells.

These results were mirrored in experiments conducted with mice. After administering injections to provoke an inflammatory response, male mice displayed quicker pain resolution, while female mice did not. Furthermore, male mice recovered faster from minor surgical procedures as well as from being temporarily restrained, mirroring the stress experienced in a car accident.

Throughout all experiments, active white blood cells producing interleukin-10 were significantly more prevalent in male mice.

Gregus suggested that these findings could reflect evolutionary distinctions between the sexes.

“It builds upon earlier studies indicating that men generally utilize their innate immune systems more effectively than women,” she explained. (The innate immune system serves as the body’s primary defense against pathogens.)

Curatolo, however, cautioned that these differences shouldn’t be viewed in black-and-white terms, as men can also experience enduring pain.

Ultimately, Laumet believes that these insights might pave the way for new treatments for chronic pain specifically in women, such as testosterone patches. He indicated that topical treatments often entail fewer side effects compared to systemic drugs.

Presently, many chronic pain relief methods come with worrying side effects and may not fully address symptoms. Prolonged use of over-the-counter painkillers can cause kidney issues or ulcers. Opioids, typically a last resort, carry addiction risks. Sometimes, doctors may prescribe antidepressant or anti-seizure medications off-label for pain, but not all patients respond effectively. Physical therapy or acupuncture also varies in effectiveness among patients.

“We clearly need alternative options,” Gregus asserted.