Gender counts in muscle, bone care, studies say

Washington -- Evidence continues to build indicating that sex matters in all aspects of health, including musculoskeletal health, and those differences go deep into the body's cells and molecules.

Yet sex-specific differences are rarely considered when treatment is provided for such common conditions as arthritis, osteoporosis and fractures, according to an article in the July Journal of Bone and Joint Surgery.

The article was based on a four-day workshop held last year by the Women's Health Issues Committee of the American Academy of Orthopaedic Surgeons, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the Office of Research on Women's Health at the National Institutes of Health.

Musculoskeletal problems account for a large number of visits to primary care physicians. It is also one area of medicine in which sex could most influence treatments and outcomes, according to research presented at the workshop.

Differences are seen in injury mechanism, pain sensation, drug actions and in rates of healing. And these differences can't be explained by hormones alone. Inherent biological variations at the cellular and molecular levels are at work, researchers said.

"This has major implications on how women and men should be treated pre- and postoperatively, not only in terms of prescribing medication types and dosages but also in terms of determining the appropriate level and frequency of analgesia and rehabilitation," said Laura Tosi, MD, former chair of the AAOS Women's Health Issues Committee and an organizer of the workshop.

Participants based many of their discussions on some basic and indisputable characteristics of men and women. For example, men tend to be taller than women because boys and girls stop growing at different ages. This phenomenon is related to sex-specific behavior of cells and genes and leads to differences in peak bone mass. It also tends to make women more vulnerable to osteoporosis.

Emerging implications

The researchers also looked at the dissimilar patterns of athletic injuries between the sexes. As men and women mature, their muscle formation, use and joint stability differ. Females are more limber and use their muscles differently from men, researchers said, and this may explain why women have more anterior cruciate ligament injuries.

Research also indicates that the stage of a woman's menstrual cycle could have an effect on such injuries.

The presence of two X chromosomes also might explain why some genetic diseases seem less serious in girls. "Depending on the amount of suppression of the bad allele, girls can have huge variation in disease presentation," Dr. Tosi said. "But in a male it's either on or off."

Cancer also affects men and women in distinct ways. For example, males develop 60% more primary musculoskeletal tumors than females, and females with such tumors have a nearly 15% better chance of survival than do males.

Although such findings are widely recognized by researchers, this information has not always made the jump to the clinical side of medicine, and treatment models are still based, for the most part, on studies of men, conference organizers said.

"I've been very aware of these differences," said Adele Boskey, PhD, director of the mineralized tissue laboratory at the Hospital for Special Surgery in New York City and one of the workshop organizers. "What got me involved was hearing a talk by a prominent orthopedic surgeon who told a group of residents, 'We have to be very careful to treat men and women alike.' "

"But that's not true," she said. "We have to get the word out that there is a difference."

At first clinicians are surprised when they hear this message. "But then they think, of course, it makes sense,'" said Barbara Boyan, PhD, a deputy director of research for the Center for the Engineering of Living Tissues at Georgia Institute of Technology and another workshop organizer. "I think it's just drawing it to their attention that opens up their eyes."

The need for more research on women was one obvious outcome from the workshop, Dr. Tosi said.

She was surprised to learn, for instance, that there are no sex-specific tools for analyzing the risk of bone fracture among women with breast cancer. The tool that is used was developed for men using data from men with prostate cancer.

"Yet women metastasize differently and their bones may break differently, but the same analytical tool is used? No, no, no, no, no," she said.

"If it can be made imperative over the next 10 years for researchers to stratify their data and include women in the various phases of the age span, we will hopefully get better research, better numbers and make better recommendations," Dr. Tosi said.