Incidence of Physician-diagnosed Osteoarthritis Among Active Duty United States Military Service Members

Objective: To examine the incidence of osteoarthritis and the influence of demographic and occupational factors associated with this condition among active duty US service members between 1999 and 2008.

Methods: To determine the total number of incident cases of osteoarthritis, the Defense Medical Surveillance System (DMSS) was queried by sex, race, age, branch of military service, and rank using code 715 of the International Classification of Diseases, Ninth Revision, Clinical Modification. Multivariable Poisson regression analysis was used to estimate incidence rates, rate ratios, and 95% confidence intervals (95% CIs) for osteoarthritis per 1,000 person-years.

Results: A total of 108,266 incident cases of osteoarthritis were documented in the DMSS within a population that experienced 13,768,885 person-years at risk of disease during the study period. The overall unadjusted incidence rate among all active duty US service members during the study period was 7.86 cases per 1,000 person-years. Significant demographic and occupational risk factors for osteoarthritis included sex, age, race, branch of service, and rank (P<0.001). Women experienced an adjusted incidence rate for osteoarthritis that was nearly 20% higher than that for men (rate ratio 1.19 [95% CI 1.17-1.21]). Service members ages≥40 years experienced an adjusted incidence rate for osteoarthritis that was ∼19 times higher than that for those ages<20 years (rate ratio 18.61 [95% CI 17.57-19.57]). Black service members experienced significantly higher incidence rates of osteoarthritis than those in the white and "other" race categories.

Conclusion: Rates of osteoarthritis were significantly higher in military populations than in comparable age groups in the general population.