April 20, 2004 — Obesity increases the risk of developing rotator cuff tears, tendinitis, and other related shoulder injuries, according to a study by University of Utah School of Medicine researchers.

“Rotator cuff tears are quite common and yet we know very little about what causes or contributes to them,” said Kurt T. Hegmann, M.D., M.P.H., research associate professor of family and preventive medicine and the study’s principal author.

Research results, published in the Journal of Bone and Joint Surgery this month, show that the more obese a person is, the greater the risk for rotator cuff tendon tears.

Hegmann, director of the Rocky Mountain Center for Occupational and Environmental Health at the U medical school’s Department of Family and Preventive Medicine, said the study helps refute a common misconception that rotator cuff tears are mainly experienced by athletes, such as baseball players who overuse their shoulders.

Hegmann said shoulder problems become more common with age, but especially among obese people. “We suspect that the cause could be either the extra weight that the arm carries, or it could be an impairment of the blood supply to the tendon, or both,” he said. Overweight is defined as having a body mass index (BMI) of 25-30, and obesity, as having a BMI of more than 30. According to 1999 national statistics, 61 percent of the American adult population is either overweight or obese.

The study involved a case group of 311 patients, ages 53-77, who underwent rotator cuff surgery, arthroscopy, and/or other repair of the shoulder at LDS Hospital in Salt Lake City from 1992 to 2000. It also included a control group of 933 healthy Utah residents, ages 55-74, enrolled in the National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian Cancer screening trial from 1994-2000, a study that is under way at the University of Utah.

The shoulder bones are held in place by muscles, tendons, and ligaments. The rotator cuff is composed of tendons that, together with muscles, hold the ball at the top of the upper arm bone (humerus) in the socket (glenoid) and gives mobility to the shoulder joint. A person with rotator cuff injury usually feels pain in the shoulder joint, especially when the arm is raised or extended out. About 4 million Americans seek medical care every year for shoulder sprain, strain, dislocation, and other problems.

In addition to Hegmann, the other investigators in the study are: Aaron M. Wendelboe, M.S.P.H.; Lisa H. Gren, M.S.P.H.; Stephen C. Alder, Ph.D., assistant professor; George L. White Jr., Ph.D., M.S.P.H., professor and program director; and Joseph L. Lyon, M.D., M.P.H., professor, all from U medical school’s public health program.