Case subjects and age-matched (within 5 years) control subjects will be recruited under a protocol approved by the Johnson and DeBakey VA Medical Centers, and the Medical University of South Carolina (MUSC) Human Investigation Review Board. All patients will be provided a written informed-consent form for their signature of acceptance before participation in the study. The case subjects and the control subjects will be derived from military service Veteran populations. The following criteria will be used for inclusion and exclusion, sample size, and recruitment of subjects in the study based on a previous, successful study conducted by the investigators' consultant, Dr. A O Edwards.