Estimated incidence of multiple sclerosis among United States Armed Forces personnel using the Defense Medical Surveillance System.

Background: The comprehensive longitudinal medical records of the U.S. Armed Forces provide a valuable tool to study the epidemiology of multiple sclerosis (MS) in persons from a diverse demography.

Objective: This study's objectives were to estimate the frequencies, incidence rates (IRs), trends, and correlates of MS among active component U.S. military members from 2000 to 2009.

Methods: An International Classification of Diseases, 9th Revision, code algorithm was used to identify MS cases from the Defense Medical Surveillance System database. IRs were determined by dividing the number of cases of MS by the total person-time of the active component during each year.

Results: During the 10-year period, there were 1,827 incident cases of MS with an overall IR of 12.9 per 100,000 person-years (p-yrs). Black non-Hispanics had a higher IR: (18.3 per 100,000 p-yrs) than White non-Hispanics (12.5 per 100,000 p-yrs). The incidence of MS by birth month and geographic home did not show a clear trend of seasonality or latitudinal gradient.

Conclusions: This investigation is the first longitudinal study of MS incidence in U.S. Armed Forces personnel. The study demonstrates higher IRs than seen in other populations and reveals a novel pattern of MS incidence by race.