DISEASES OF THE BLOOD AND BLOOD-FORMING ORGANS

Diseases of the blood and blood forming organs include conditions affecting blood cells (erythrocytes, leukocytes, platelets) as well as the organs where these cells are produced (bone marrow, lymph nodes, spleen). The etiology of these disorders is varied, including genetic conditions, exposure to toxins and medications, infections or nutritional deficiencies. Diseases of the blood were not considered separately from other conditions in Volume 4, thus, this section does not include a summary of that volume. Primary studies are summarized in Table 4-2.

Updated and Supplemental Literature

Primary Studies

A number of studies have compared hospitalizations for diseases of the blood in veterans deployed and nondeployed to the Gulf War. For the purpose of this review, those studies have been considered primary. In addition to hospitalization studies, three published reports have examined hematologic parameters using laboratory tests in deployed and nondeployed Gulf War veterans.

Gray et al. (1996) used a retrospective cohort approach comparing hospitalizations among 547,076 Gulf War deployed and 618,335 nondeployed active-duty personnel at DoD medical facilities. Hospitalizations for 14 ICD-9-CM diagnostic categories, which included “diseases of the blood,” were assessed across three time periods following the war: August 1, 1991, to December 31, 1991; January 1, 1992, to December 31, 1992; and January 1, 1993, to September 30, 1993. Hospitalizations for diseases of the blood, primarily anemia, were increased among the Gulf War deployed personnel (vs nondeployed) during 1992 only. Differences, however, were not consistent over time and could be accounted for by deferred diagnoses during deployment. Limitations of this study include the relatively short follow-up, the lack of outpatient data, restriction to DoD hospitals, restriction to hospitalizations of those who remained on active duty after the war, and limited adjustment for potential confounders.

A later publication expanded the previous study to include hospitalizations for reservists and separated military personnel over the same three time periods as Gray et al. (1996). In addition to examining hospitalization data from DoD hospitals, this study also included hospital stays from the VA system and the California Office of Statewide Health Planning and Development for the years 1991-1994 (Gray et al., 2000). Denominator data for this analysis (the total number of veterans in each group) were not available, which led the researchers to use proportional morbidity ratios. The results did not provide evidence that blood diseases were more frequent among deployed than nondeployed veterans. Age and sex-adjusted proportional morbidity ratios for blood diseases in deployed versus nondeployed were 1.1 (95% CI 1.0-1.2) in DoD hospitals, 0.8 (95% CI 0.5-1.0) in VA hospitals, and 1.1 (0.2-2.0) in California hospitals. This analysis is limited since outpatient diagnoses were not included. Hospitalization rates were not estimated, and the analysis did allow for adjustment for confounding.

Hospitalizations for blood disorders were examined in an additional study comparing hospitalization rates in DoD hospitals through 2000 in three cohorts of veterans: Gulf War veterans, veterans deployed to Southwest Asia after the Gulf War, and veterans deployed to Bosnia (Smith et al., 2006). After adjustment for sex, age, marital status, pay grade, race/ethnicity, service branch, occupation, and predeployment hospitalizations, the rate of



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