Validity of military service as reported on U.S. death certificates

BACKGROUND: Although death certificates are widely used to study mortality in the general population, their use to study mortality among individuals with military service has been limited in part by a lack of information on the validity of military service reported on death certificates. Our objective was to estimate bias parameters for misclassification of military service to facilitate quantitative bias analysis in studies of mortality in military populations. METHODS: We included 2014-2021 death certificates from decedents aged 18-64 years who resided and died in Alabama, Michigan, Minnesota, Montana, or Oregon. Death certificates were linked to military service records by the U.S. Defense Manpower Data Center (DMDC) using Social Security Number. Military service was defined as any service in the Regular, Reserve, or National Guard components of the U.S. military in DMDC records. We estimated sensitivity, specificity, and predictive values for military service reported on death certificates stratified by demographics, military characteristics, and manner of death. RESULTS: Among the 467,075 death certificates included, 9.3% indicated military service; however, military records showed that 10.9% had served (sensitivity 81.5%, 95% confidence interval [CI]: 81.2-81.8%; specificity 99.5%, 95% CI: 99.5-99.5%). Sensitivity was lower among female (72.3%) compared to male (82.2%) servicemembers and was particularly low for those who had never served on active duty (63.5%). CONCLUSIONS: Military service was underreported on death certificates, especially for female servicemembers and those without active-duty service. The bias parameters we estimated can be used to account for this misclassification when analyzing death certificates.