The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 60:1328-1332 (2005)
© 2005 The Gerontological Society of America
Cerebrovascular Diseases as Primary Hospital Discharge Diagnoses: National Trend (1970–2000) Among Older Adults
Ali Ahmed1,
Jose Ness2,,
George Howard3 and
Wilbert S. Aronow4
1 Division of Gerontology and Geriatric Medicine, Department of Medicine, Schools of Medicine, and Department of Epidemiology and International Health, School of Public Health, Center for Aging, and Geriatric Heart Failure Clinic, University of Alabama at Birmingham, Section of Geriatrics and Geriatric Heart Failure Clinic, Birmingham VA Medical Center, and Heart Failure Project, Alabama Quality Assurance Foundation, Birmingham, Alabama.
2 Division of General Internal Medicine, Department of Internal Medicine, University of Iowa Health Care, Iowa City.
3 Department of Biostatistics, School of Public Health, University of Alabama at Birmingham.
4 Sections of Cardiology and Geriatrics, Department of Medicine, New York Medical College, Valhalla, New York, and Mount Sinai School of Medicine, New York, New York.
Address correspondence to Jose Ness, MD, University of Iowa Hospitals and Clinics, Division of General Internal Medicine, Department of Internal Medicine, SE624, GH, 200 Hawkins Drive, Iowa City, IA 52242. E-mail: jose-ness{at}uiowa.edu
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Abstract
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Background. Cerebrovascular diseases are a common cause of mortality, morbidity, and hospitalization among older adults. However, the long-term national trends in cerebrovascular disease-related hospitalizations in this age group are not well known.
Methods. We used the National Center for Health Statistics trend data from the National Hospital Discharge Surveys (1970–2000) to determine incidence of cerebrovascular disease-related hospitalizations among persons 65 years and older in the United States. Only patients discharged with a primary discharge diagnosis of cerebrovascular disease were included. We estimated rates of hospitalization per 1000 civilian residents 65 years and older, for all patients and stratified by age, sex, and race.
Results. Among persons 65 years of age and older, the total number of cerebrovascular disease-related hospitalizations increased from 372,000 in 1970 to 711,000 in 2000. However, the rates of hospitalization due to cerebrovascular disease remained unchanged at 20.7/1000 in 1970 and 20.4/1000 in 2000. The rates for persons 75–84 years and >85 years were, respectively, 2 and 3 times higher than that for persons 65–74 years throughout the study period. Rates for men and women were comparable and stable during the study period. Rates for African Americans, in contrast, increased from 14/1000 in 1970 to 20.6/1000 in 2000, peaking in 1985 (27.4/1000).
Conclusions. The overall rates of hospitalization due to cerebrovascular disease remained high yet stable. However, the absolute number of hospitalizations due to cerebrovascular disease increased considerably, with potential for serious social, financial, and public health implications for the coming decades.
STROKE is the third leading cause of death and a leading cause of chronic disability among older adults in the United States (1). Whereas earlier studies may have underestimated the incidence and prevalence of cerebrovascular disease (2), newer data suggest that as many as 750,000 strokes occur among Americans every year (3,4). Age plays an important role as a predictor of cerebrovascular disease incidence, with significant increases in stroke incidence rates taking place for every 10-year increase in age after 55 (4). Approximately one in four men and one in five women will develop cerebrovascular disease if they live to their 85th birthday (5). The proportion of older people in the community has been pointed out as a predictor of increasing cerebrovascular disease incidence (6). Male sex and being African American or Hispanic American also correlate with an increased prevalence of cerebrovascular disease (3,4).
The costs of providing care for patients suffering from cerebrovascular disease are staggering. Direct annual costs have been estimated at $17 billion, with an additional burden of $13 billion in lost earnings (7). Inpatient hospital costs are the largest component of direct costs in the acute stages of management (8). The clinical and economic implications of cerebrovascular disease justify the need for a thorough and updated understanding of the temporal trends in cerebrovascular disease-related hospitalizations in the United States among older adults, who are highly prone to the dire consequences of this devastating disease. However, the long-term national trends in the demographic correlates of hospitalizations due to cerebrovascular diseases in older Americans have not been well studied. The purpose of this study is to examine age-, sex-, and race-related variations in the trends in cerebrovascular disease hospitalizations among older adults between 1970 and 2000 in the United States.
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METHODS
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Study Sample
The individuals studied were persons 65 years of age and older, discharged with a primary discharge diagnosis of cerebrovascular disease from non-Federal short-stay hospitals in the United States between 1970 and 2000.
Cerebrovascular Disease
The diagnosis of cerebrovascular disease was determined by the International Classification of Diseases (ICD), 9th Revision, Clinical Modification (CM) codes 430–438 between 1979 and 2000. Between 1970 and 1978, the diagnosis was based on the ICD (8th Revision) codes for cerebrovascular disease.
The National Hospital Discharge Survey
The National Center for Health Statistics has been conducting the National Hospital Discharge Surveys (NHDSs) since 1965. By abstracting hospital discharge records, data are collected on medical and demographic information for calculating statistics on hospital utilization, and on the nature and treatment of illness among the hospitalized population. Until 1984, data abstraction was performed manually at the respective hospitals by hospital personnel or by Bureau of Census staff contracted by the National Center for Health Statistics. Since 1985, in addition to manual data collection, an automated system was introduced to collect data. These surveys are made available to the public annually.
Statistic Analysis
We used Beyond 20/20 (http://www.beyond2020.com) and Microsoft Excel 2000 (Redmond, WA) software programs for data analysis. The Beyond 20/20 browser allows analysis of aggregate data to customize tables and figures. At first we described the 31-year prevalence (1970–2000) of hospitalization among persons 65 years of age and older as estimated numbers and discharge rates per 1000 civilians. Discharge rates are calculated by dividing the estimated number of discharges in the population in a year by the midyear civilian resident population in the demographic group. To eliminate differences in observed values that result from differences in population composition, rates were adjusted for age to the U.S. standard population by using age-specific rates for persons 65–74 years, 75–84 years, and 85 years and older. Then, we compared the rates of discharge due to cerebrovascular disease for patients 65 years and older by 10-year age categories: 65–74 years, 75–84 years, and 85 years and older, and for all patients, stratified by sex and race.
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RESULTS
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Table 1 demonstrates the numbers of civilian residents and hospital discharges in thousands, and age-adjusted rates of hospital discharges per 1000 civilian residents 65 years of age and older due to a primary discharge diagnosis of cerebrovascular disease in the United States, between 1970 and 2000 (data for all persons and stratified by sex). The absolute number of people hospitalized with cerebrovascular disorder increased from 372,000 in 1970 to 711,000 in 2000. However, the overall rates of hospitalization per 1000 civilian residents were comparable in 1970 (20.7/1000) and 2000 (20.4/1000). The rates were somewhat higher (24–25 per 1000) during 1979–1987. Male residents had somewhat higher rates of hospitalization compared to female. However, within each individual sex group, the trends were comparable to those of the entire cohort.
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Table 1. Civilian Resident Population in 1000s, Number of Hospital Discharges in 1000s, and Age-Adjusted Rates of Hospital Discharges per 1000 Civilian Residents 65 Years of Age and Older Due to a Primary Discharge Diagnosis of Cerebrovascular Disease in the United States, 1970–2000 (Data for all Persons and Stratified by Sex).
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Table 2 displays the numbers of civilian residents and hospital discharges in thousands, and age-adjusted rates of hospital discharges per 1000 civilian residents 65 years of age and older due to a primary discharge diagnosis of cerebrovascular disease in the United States between 1970 and 2000 (data for all persons and stratified by race). The rates of hospitalization per 1000 civilian residents were higher for whites (17.8/1000 vs 14/1000 for African Americans) in 1970. However, the rate was higher for African Americans (20.6/1000 vs 15.1/1000 in whites) in 2000. During the 31-year study period, the rates of hospitalization due to cerebrovascular disease increased by 47% for African Americans and decreased by 16% for whites. The rates between the two races were comparable during the early 1980s.
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Table 2. Civilian Resident Population in 1000s, Number of Hospital Discharges in 1000s, and Age-Adjusted Rates of Hospital Discharges per 1000 Civilian Residents 65 Years of Age and Older Due to a Primary Discharge Diagnosis of Cerebrovascular Disease in the United States, 1970–2000 (Data for All and Stratified by Race).
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Figure 1 demonstrates that age was positively associated with higher rates of hospitalization due to cerebrovascular disease during the entire study period. Figure 2 demonstrates that white males had the highest rate of hospitalization between 1970 and 1984. After that, African-American female patients had the highest rate of hospitalization for the rest of the study period. African-American males, in contrast, had the lowest rate during the 1970s (less than half the rate of whites). However, during the late 1990s, the rates for African-American males were comparable or even lower than those of white males.
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Figure 1. Rates of hospitalization per 1000 civilian residents due to cerebrovascular disease as the primary discharge diagnosis between 1970 and 2000 in the United States by age category 65–74 years, 75–84 years, and 85 years and older
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Figure 2. Age-adjusted rates of hospitalization per 1000 civilian residents due to cerebrovascular disease as the primary discharge diagnosis between 1970 and 2000 in the United States by sex and race
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DISCUSSION
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One of the major findings of our analysis is that, although overall rates of hospitalization for Americans 65 years and older with cerebrovascular disease as the primary discharge diagnosis have remained high and stable during the past three decades, the absolute numbers of hospitalizations have increased significantly during this time. These findings have multiple public health implications for American older adults.
With the aging of the U.S. population in general, and the increase of the number of those persons 85 years and older in particular, the total number of persons developing cerebrovascular disease is likely to increase over the next several decades, leading to a subsequent growth in the total number of cerebrovascular disease-related hospitalizations. We observed that rates of hospitalization due to cerebrovascular disease increased with aging, and this association remained unchanged during the past three decades. In a previously published analysis of overall stroke hospitalization trends in the United States between 1988 and 1997 (9), a temporal increase in the number of hospitalizations was noticed among people aged 65 and older but not among younger patients. However, in that study, the rates of hospitalization for persons 85 years and older were not studied. We noted that rates of hospitalization were the highest among people 85 years and older, suggesting that the oldest old are particularly vulnerable to the burden of cerebrovascular disease. This finding is consistent with the results of a large population-based study where 36.6% (1316/3594) first-ever ischemic strokes occurred in patients 80 years old or older, accounting for one-third of health care utilization and for 59.8% of deaths within 30 days (10).
The increasing rates of hospitalization due to cerebrovascular disease among African Americans are rather alarming, as many of the modifiable stroke risk factors, such as hypertension and diabetes, are particularly common in this ethnic group (11,12). The incidence of cerebrovascular disease is known to be higher among younger African Americans (13). In a cohort of 15,792 men and women 45–64 years followed for approximately 7 years, there were 267 incident cerebrovascular disease cases, of which 221 (83%) were ischemic strokes, and the age-adjusted rate ratio for ischemic stroke was higher (2.41; 95% confidence interval: 0.85, 3.15) among African Americans (vs whites). The association was weakened after adjustment for baseline hypertension, diabetes, educational level, smoking status, and prevalent coronary heart disease (age-adjusted rate ratio: 1.38; 95% confidence interval: 1.01, 1.89). Our results reveal higher rates of cerebrovascular disease-related hospital discharges among elderly African Americans, reinforcing the need for targeted and intensive interventions to manage modifiable risk factors for cerebrovascular disease in this population (14). Howard and colleagues (15) are currently recruiting over 30,000 participants in the National Institute for Neurological Disorders and Stroke-funded study REasons for Geographic And Racial Differences in Stroke (REGARDS). The results of this prospective follow-up study will provide critical data about stroke risk factors, incidence, and mortality rates among African Americans and whites throughout the United States (15).
We observed a significant increase in rates of hospitalization during 1978–1979. Even though the NHDS data sets have used comparable diagnostic groups to enable tracking trends through the years spanning the use of both ICD coding systems, changes in the discharge rates of cerebrovascular disease between 1978 and 1979 could still be due to the coding system transition from ICD-8 to ICD-9 codes (16,17). Of note, the introduction of the new Medicare Prospective Payment System in 1983 influenced both hospitalization practices and disease reporting on discharge records (18), but was not temporally associated with an increase in rates of hospitalization in our study.
Our study suffers from several limitations. Long-term and federal hospitals are not included in the sample, leading to an underestimation of the total number of hospitalizations associated with cerebrovascular disease (19). We are also unable to ascertain if the distribution of such hospitalizations among the different types of facility has changed over time. Hospital discharges (not individuals) are sampled, and patients who are hospitalized more than once will be counted correspondingly (19). The results of our study related to racial variations should also be interpreted with caution. The data on race in the NHDS data sets have become increasingly incomplete in recent years. During the 1980s, race was not reported in about 10% of the discharges, in about 16% in 1990, and in about 18% in the 1990s. About 25% of the discharges in 2000 had missing data on race (20). Discharges of white patients are probably more likely to be underreported than those of other racial groups and likely had a minimal impact on the findings related to African Americans. A substantial shortcoming of the NHDS data is that initial hospitalizations cannot be distinguished from hospitalizations for subsequent events. A decline in case fatality during the study period (21–23) would likely be associated with a larger number of cerebrovascular disease survivors in the population. Because stroke survivors are at substantially higher risk for additional cerebrovascular disease (24), it is possible that the lack of a temporal decline in hospitalized stroke is a product of repeated stroke in an increasing population of stroke survivors. Finally, our study does not address stroke hospitalization among patients younger than 65 years of age, who account for a significant number of stroke hospitalizations.
Conclusion
We observed that, over the past three decades, the rates of hospitalization have increased for African Americans and with increasing age. We also observed that, although the overall rates were stable, the absolute numbers of hospitalizations due to cerebrovascular disease have increased remarkably and that this is likely to have a serious impact on the care of older adults suffering from this disabling condition.
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Footnotes
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Decision Editor: John E. Morley, MB, BCh
Received May 7, 2004
Accepted August 2, 2004
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Abstract
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