Hospital Discharge Rates for Cerebrovascular Disease -- United States, 1970-1986

Despite a nearly 50% decline in cerebrovascular mortality in the past 30 years, stroke remains the third leading cause of death and continues to be a major public health problem in the United States. The direct health-care costs of stroke were estimated to be approximately $3.3 billion annually in 1976 (1). Hospitalizations represent more than one third of those costs.

This report describes national trends in hospital discharge rates from 1970 to 1986 for cerebrovascular disease and its components. The annual number of hospital discharges was determined from the first-listed diagnosis in the National Hospital Discharge Survey (NHDS) (2) of CDC's National Center for Health Statistics (NCHS).* Data for the NHDS are obtained from a multistage, stratified cluster sample of discharges from nonfederal short-stay hospitals in the 50 states and the District of Columbia. The NHDS collects approximately 200,000 records a year. Each year, 3237-4577 patients in the sample were discharged with a first-listed diagnosis of cerebrovascular disease. Population estimates were determined from data provided by the Bureau of the Census (5) and Demo-Detail** (6).

The general category of cerebrovascular disease under both ICDA-8 and ICD-9-CM includes all discharged persons with a first-listed diagnosis of 430 through 438 (3,4). This grouping was subdivided for further analysis as follows: intracranial hemorrhage (ICDA-8: 430-431; ICD-9-CM: 430-432); occlusion of cerebral arteries (ICDA-8: 433-434; ICD-9-CM: 434); transient cerebral ischemia (ICDA-8 and ICD-9-CM: 435); acute ill-defined cerebrovascular disease (ICDA-8 and ICD-9-CM: 436); and other cerebrovascular disease (ICDA-8: 432, 437-438; ICD-9-CM: 433, 437-438) (7).

Observed changes in hospital discharge rates from 1978 to 1979 reflect a mixture of procedural changes in coding practices and real changes in hospitalization rates.*** For this reason, the following descriptions of trends from 1970 through 1986 omit changes in rates from 1978 to 1979 (Figures 1 and 2).

From 1970 through 1986, hospital discharge rates per 100,000 population for cerebrovascular disease ranged from a low of 254 in 1970 to a high of 384 in 1985. Hospital discharges per 100,000 population for cerebrovascular disease increased an average of 4.9 per year from 1970 through 1986. Rates increased every year except 1974-1975 and 1985-1986.

Trends in hospital discharges per 100,000 population varied among the components of cerebrovascular disease. For intracranial hemorrhage, rates decreased from 26 in 1970 to 19 in 1976, then increased to 32 in 1986. For occlusion of cerebral arteries, rates remained relatively constant from 1970 through 1983, then rose from 45 in 1983 to 81 in 1986. For transient cerebral ischemia, rates increased from 12 in 1970 to 22 in 1978 and from 76 in 1979 to 88 in 1986 (with a peak of 94 in 1983). For acute ill-defined cerebrovascular disease, rates climbed fro 97 in 1970 to 119 in 1978 and from 99 in 1979 to 121 in 1984; they declined to 104 in 1985 and to 92 in 1986. For other cerebrovascular diseases, hospital discharge rates increased from 75 in 1970 to 87 in 1972, fluctuated between 87 and 93 through 1984, then declined to 76 in 1986. Reported by: Office of Surveillance and Analysis, Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note

Editorial Note: This report uses data on hospitalizations to identify trends for one important aspect of the health-care burden of cerebrovascular disease. Hospital discharge rates reflect a variety of influences and often do not correspond to trends in incidence or mortality rates (8). Since 1970, stroke mortality in the United States has declined. This change has been attributed in part to declining incidence resulting from improvements in the detection and control of hypertension (9-11). The data in this report showed an increase in cerebrovascular disease hospitalization rates from 1970 through 1984. Additional evidence suggests that an increased detection of milder strokes may have contributed to increasing hospitalization rates (12,13). Declining hospitalization rates after 1984, together with declining mortality and case-fatality rates, may indicate a declining prevalence of disease.

This analysis showed the greatest decline in discharge rates after 1983 in the less specific disease categories (other cerebrovascular disease, acute ill-defined cerebrovascular disease, and transient cerebral ischemia) and the largest increases in discharge rates in the more specific diagnostic categories (intracranial hemorrhage and occlusion of cerebral arteries). Thus, the introduction of diagnostic related groups, which became widely used after 1983, may have stimulated increased use of more specific diagnoses. Increases in the use of computerized tomography and in elective hospitalization for endarterectomy may also have contributed to increased recognition of intracranial hemorrhage and occlusion of cerebral arteries from 1983 through 1986.

References

1. Goldstein M. Cerebrovascular epidemiology--economic factors. J Neuroradiol 1983;10: 160-4. 2.National Center for Health Statistics. National Hospital Discharge Survey (machine-readable data files). Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, 1970-1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986. 3.National Center for Health Statistics. International classification of diseases, adapted for use in the United States. Eighth revision. Washington, DC: US Department of Health, Education, and Welfare, Public Health Service, 1968; PHS publication no. 1693. 4.Health Care Financing Administration. The international classification of diseases. Ninth revision: clinical modification. 2nd ed. Washington, DC: US Department of Health and Human Services, Public Health Service, 1980; DHHS publication no. (PHS)80-1260. 5.Bureau of the Census. 1970-1980 intercensal population estimates by race, sex, and age (machine-readable data files). Washington, DC: US Department of Commerce, Bureau of the Census, nd. 6.Irwin R. 1980-1986 intercensal population estimates by race, sex, and age (machine- readable data file). Alexandria, Virginia: Demo-Detail, 1987. 7.Duggar BC, Lewis WF. Comparability of diagnostic data: coded by the eighth and ninth revisions of the International Classification of Diseases. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, 1987; DHHS publication no. (PHS)87-1378. 8.CDC. Hospital discharge rates for four major cancers--United States, 1970-1986. MMWR 1988;37:585-8. 9.Garraway WM, Whisnant JP, Drury I. The continuing decline in the incidence of stroke. Mayo Clin Proc 1983;58:520-3. 10.Garraway WM, Whisnant JP, Drury I. The changing pattern of survival following stroke. Stroke 1983;14:699-703. 11.Garraway WM, Whisnant JP. The changing pattern of hypertension and the declining incidence of stroke. JAMA 1987;258:214-7. 12.Gillum RF. Cerebrovascular disease morbidity in the United States, 1970-1983: age, sex, region, and vascular surgery. Stroke 1986;17:656-61. 13.Robbins M, Baum HM. Incidence. In: Weinfeld FD, ed. Report on the National Survey of Stroke. Stroke 1981;12(suppl 1):145-57. *Diagnoses for 1970-1978 are based on he International Classification of Diseases (ICD), Eighth Revision, Adapted (ICDA-8) (3); those for 1979-1986, on the ICD, Ninth Revision, Clinical Modification (ICD-9-CM) (4). **Use of trade names is for identification only and does not imply endorsement by the Public Health Service or the U.S. Department of Health and Human Services. ***To assess the effects of changes in coding practices from ICDA-8 to ICD-9-CM, NCHS calculated comparability ratios for various diseases, including cerebrovascular diseases. The comparability ratio of a disease entity is defined as the ratio of the number of cases coded to a set of ICD codes under the old coding procedures to the number of cases coded to a set of codes (not necessarily identical) under the new coding procedures, when the coding procedures are applied to the same cases. To obtain its comparability ratios, NCHS recoded data from 1975 using ICD-9-CM procedures. Even the adjusted rates seem to be affected by changes in coding procedures from ICDA-8 to ICD-9-CM and therefore are not used in this report.

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