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2008 Atlas of Stroke Hospitalizations Among Medicare BeneficiariesSection Seven: Maps At-a-Glance
In this section, we placed multiple maps on a page to enhance the reader’s ability to visually compare geographic patterns. To ease visual comparison across maps in this section, we only included the continental United States, and we omitted the frequency distribution graphs. Stroke SubtypesIschemic Stroke—a stroke caused by a deficiency of blood to the brain, usually due to the functional constriction or blockage of a blood vessel. Hemorrhagic Stroke—a stroke caused by the escape of blood (bleeding) to the brain, usually due to the rupture of a blood vessel. Ill-Defined Stroke—diagnosis or classification used when there is not enough medical information to classify a stroke as ischemic or hemorrhagic. Two-thirds (67.0%) of the stroke hospitalizations among Medicare beneficiaries in this Atlas were ischemic, 11.6% were hemorrhagic, 20.3% were ill-defined, and 1.1% were late effects from a stroke (Figure 7.1). Hospitalizations due to late effects from a stroke were not mapped in this Atlas because the numbers are too small to produce stable county-level rates. Figure 7.1 Percentage of stroke hospitalizations, by stroke subtype—Medicare beneficiaries ages 65 and older, 1995–2002
Discharge StatusFor this section, the first set of maps compares the geographic patterns of different discharge destinations for the total population of Medicare beneficiaries in this study. The next sets of maps compare the geographic patterns for each discharge destinations by race/ethnicity. Discharge Destinations*
* Categories of discharge destination defined by Centers for Medicare & Medicaid Services. Figure 7.2 Percentage of stroke hospitalizations, by discharge status—Medicare beneficiaries ages 65 and older, 1995–2002
Selected ComorbiditiesFor this section, the first set of maps compares the geographic patterns of hypertension, diabetes, and atrial fibrillation for the total population of Medicare beneficiaries in this Atlas. The next sets of maps compare the geographic patterns for each of the selected comorbidities by race/ethnicity. Figure 7.3 Percentage of stroke hospitalizations with selected comorbidities—Medicare beneficiaries ages 65 and older, 1995–2002
Selected Comorbidities
Among the stroke hospitalizations examined in this Atlas, 61.3% included a diagnosis of hypertension, 24.7% included a diagnosis of diabetes, and 18.7% included a diagnosis of atrial fibrillation (Figure 7.3). A Note on MethodsStroke hospitalizations were defined as those for which the principal diagnosis on the Medicare hospital claim form was cerebrovascular disease, indicated by codes 430–434 and 436–438 according to the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM). Hospitalizations for which the principal diagnosis was transient ischemic attacks (ICD-9-CM code 435) were excluded. For each map, the counties are categorized according to quintile; the darkest color represents counties with the highest rates or percentages (depending on the data being presented), and the lightest color represents counties with the lowest rates or percentages. All county-level rates and percentages have been spatially smoothed to enhance the stability in counties with small populations. Counties are categorized as having “insufficient data” if the sum of stroke hospitalizations in the index county plus the neighboring counties is less than 20 or if the Medicare population is less than 10. For percentages, a relative standard error >30% is an additional criterion for categorizing a county as having insufficient data. For a detailed explanation of the methods, see Appendix B. A Cautionary NoteIn the Medicare data sets, the accuracy of codes for Hispanic race and ethnicity is limited because these codes are not reported separately. For example, a person who is white and Hispanic is reported as either white or Hispanic. This reporting practice can result in misclassification of race and ethnicity. According to 1996 data, the probability that the racial/ethnic designation on Medicare claim forms is correct is 96.6% for whites and 95.5% for blacks, but only 19.4% for Hispanics. At the same time, the probability that a person identified as Hispanic in the Medicare data set is actually Hispanic is 98% (Arday SL, Arday DR, Monroe A, Zhang MD. HCFA’s racial and ethnic data: current accuracy and recent improvements. Health Care Financing Review 2000;21[4]:107–16). Together, these data suggest that Hispanics are underreported in the Medicare data sets and that this underreporting could introduce bias into the results presented here. Links to the Different MapsStroke Hospitalization Rates for the Total Population Stroke Hospitalization Rates for All Strokes Stroke Hospitalization Rates for Ischemic Stroke Stroke Hospitalization Rates for Hemorrhagic Stroke Stroke Hospitalization Rates for Ill-defined Stroke Stroke Hospitalizations by Discharge Status
Stroke Hospitalizations: Discharged Home Stroke Hospitalizations: Discharged to a Skilled Nursing Facility Stroke Hospitalizations: Discharged to Other Care Facility Stroke Hospitalizations: Discharged to Any Care Facility Stroke Hospitalizations: Died Before Discharge Stroke Hospitalizations: Died Within 30 Days Stroke Hospitalizations: Selected Comorbidities Stroke Hospitalizations: Hypertension Stroke Hospitalizations: Diabetes Stroke Hospitalizations: Atrial Fibrillation
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