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Stress fracture risk varies by race, sex
White U.S. Army soldiers were more likely to sustain a stress fracture over 10 years vs. soldiers of other races, with the highest risk observed among white women, according to findings from a retrospective cohort study.
“The increased granularity of the race-based analyses in this study provides a more in-depth description of race/ethnic origin as a risk factor for stress fractures,” Lakmini Bulathsinhala, MPH, of the military performance division of the U.S. Army Research Institute of Environmental Medicine in Natick, Massachusetts, and colleagues wrote. “Importantly, the results of this study showed that for both sexes, non-Hispanic white soldiers have the highest risk of stress fracture, non-Hispanic black soldiers have the lowest risk, and Hispanic soldiers possess a comparatively intermediate risk.”
Bulathsinhala and colleagues analyzed 21,549 stress fracture cases in 1,299,332 soldiers, using records from the Total Army Injury and Health Outcomes Database between 2001 and 2011 (63.76 white; 17.38% black; 10.3% Hispanic). Researchers used Cox-proportional hazard models to calculate the time until stress fracture stratified by race, adjusting for age, education and BMI.
During 5,228,525 person-years of risk, researchers found the overall incidence rate for stress fractures was 4.12 per 1,000 person-years, with a 3.6-fold higher rate among women vs. men (7.45 vs. 2.05 per 1,000 person-years). Those of mixed race had the highest crude incidence rate of stress fracture (5.4 per 1,000 person-years), followed by American Indian/Native Alaskan soldiers (5.1 per 1,000 person-years) and white soldiers (4.7 per 1,000 person-years).
Researchers found that white soldiers had the highest risk for stress fracture. Compared with black soldiers as a reference group, white men had a 59% higher risk; white women had a 92% higher risk. The second highest risk group was Hispanics, with Hispanic men and women having a 19% and 65% greater risk for stress fracture, respectively, compared with black soldiers. Among American Indian/Native Alaskan and Asian soldiers, only women showed an increased stress fracture risk vs. black soldiers, with a 72% and 32% increased risk, respectively.
Researchers also found that younger soldiers (aged 20 years or younger) were more likely to sustain a stress fracture vs. those aged 20 to 30 years; OR for men was 5.98 (95% CI, 5.69-6.28); OR for women was 4.71 (95% CI, 4.47-4.96). However, men and women aged at least 30 years had a 61% and 53% lower risk, respectively, for sustaining stress fracture vs. younger adults. Body weight also played a role in stress fracture risk; men with obesity had a 24% increased risk for stress fracture vs. those with a normal BMI (OR = 1.24; 95% CI, 1.17-1.31).
“These findings provide a more in-depth analysis of the differences in risk of stress fracture by race-origin, which contributes to a better understanding of who may be at greatest risk of stress fracture in the U.S. Army,” the researchers wrote. “This type of information can also help medical providers with differential diagnoses and appropriate workup for musculoskeletal overuse or stress injuries. The factors that contribute to the different risk of stress fracture by racial/ethnic origin remain to be elucidated.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.