Nationwide cerebrovascular disease mortality study. I. Methods and analysis of death certificates

Invited Commentary: Heterogeneity of Cardiovascular Diseases Among Populations-Recognition and Seminal Explanations

Kuller and Reisler's 1971 publication (Am J Epidemiol. 1971;93(1):1-9) was an important contribution to the understanding of the epidemiology of cardiovascular diseases, particularly stroke. The authors synthesized pathological and risk-factor evidence to theorize why rates of various subtypes of arterial disease might vary across populations. Specifically, they suggested that different population levels of blood pressure, lipids, and glucose led to population differences in the location and extent of arterial disease. The publication is an excellent model of how to integrate data on person, place, and time of a major public health problem, together with information on pathology and factors that determine individual risk, to derive a coherent explanation for population patterns in cardiovascular disease. The authors' basic theory has proven solid for the past 5 decades.

Increasing hospital admission rates for intracerebral hemorrhage during the last decade

BACKGROUND

The incidence and mortality of all types of strokes, including intracerebral hemorrhages, declined during the 1970s. However, some evidence exists that these trends stabilized or reversed during the 1980s. In the present study, a large North American population was observed from 1981 to 1989 to assess changes in the annual hospital admission rates of intracerebral hemorrhage.

METHOD

Data provided by the Connecticut Health Information Management and Exchange (CHIME, Wallingford, Connecticut), a state-wide clinical database of records submitted voluntarily by all of Connecticut's 36 acute care, nongovernment hospitals, was analyzed for all patients with primary diagnosis of intracerebral hemorrhage (ICD-9-CM=431) for the fiscal years 1981, 1983, 1985, 1987, 1988, and 1989.

RESULTS

During the time periods studied, there were 3,277 hospitalizations with a primary diagnosis of intracerebral hemorrhage. There was an initial annual hospital admission rate of 12 per 100,000 in 1981. Rates steadily increased to nearly 20 per 10,000 in 1988 and 1989. This increase in hospital admission rates from intracerebral hemorrhage was statistically significant when the data were adjusted for gender, race, and age (P<.001). When admission rates for intracerebral hemorrhage were stratified by age, admission rates increased dramatically only in those 65 years and older (P<.001). The in-hospital death rate decreased during the study decade (P=.004); however, age-adjusted analysis indicated that in-hospital deaths increased significantly (P<.001) in patients 65 years and older.

CONCLUSIONS

Hospital admission rates for intracerebral hemorrhage nearly doubled from 1981 to 1989. This change may be due to an actual increase in the annual incidence of intracerebral hemorrhage caused by mechanisms that are not yet fully understood.

Comparison of additive and multiplicative models of regional variation in the decline of stroke mortality in the United States

BACKGROUND AND PURPOSE

Although previous studies have shown that geographic variation in the decline of stroke mortality rates may be an important contributor to the changing geographic distribution of stroke mortality in the United States, some concern has been raised that this phenomenon may be model dependent. This study examines the geographic variation in the decline of stroke mortality rates in the United States with the use of both additive and multiplicative models.

METHODS

National Center for Health Statistics and Bureau of the Census data were used to assess regional-level temporal trends of underlying-cause stroke mortality rates in the United States for 1979 through 1989. Both additive and multiplicative models were fit to the data.

RESULTS

Underlying-cause stroke mortality rates have declined fairly steadily in all regions of the United States and for all race-sex groups, although there was significant regional variation in the rate of decline during the period 1979 through 1989. The South, which initially had the highest rates, had the most rapid decline for all race-sex groups when either additive or multiplicative models were used.

CONCLUSIONS

From 1979 through 1989 there was significant geographic variation in the rate of decline of stroke mortality rates, with the most rapid rates of decline in the South. As a result, there has been a decrease in interregional variation in stroke mortality rates.

Geographic variation in reporting of stroke deaths to underlying or contributing causes in the United States

BACKGROUND AND PURPOSE

This study examines the geographic variation in the reporting of deaths with stroke as the underlying or contributing cause in the United States.

METHODS

Data from the National Center for Health Statistics and Bureau of the Census were used to map the geographic distribution of race- and race/sex-specific, underlying-, contributing-, and multiple-cause age-adjusted stroke mortality rates in the United States by state for 1979 through 1981.

RESULTS

Underlying-, contributing-, and multiple-cause age-adjusted stroke mortality rates were significantly clustered for both whites and blacks. However, the spatial distributions of underlying- and contributing-cause rates differed; there was no association between underlying- and contributing-cause rates for either racial group or for the various race/sex groups. There was no association between nonstroke mortality and stroke mortality rates. There was also very little spatial variation and no spatial clustering of the median number of contributing causes reported.

CONCLUSIONS

The overall large-scale spatial distribution of resident underlying-cause stroke mortality rates cannot be explained by geographic variation in the selection of the underlying cause of death from among all causes reported on the death certificate, by different area-dependent tendencies for mortality generally, or by different tendencies to consider stroke as the cause of death when death occurs. Geographic variation in contributing-cause rates is not explained by variation in tendency to report contributing causes of death.

Geographic variation in the decline of stroke mortality in the United States

BACKGROUND AND PURPOSE

This study examines the geographic variation in the decline of stroke mortality rates in the United States.

METHODS

National Center for Health Statistics and Bureau of the Census data were used to assess regional and state level temporal trends of stroke mortality in the United States for 1970 to 1989.

RESULTS

Underlying- and multiple-cause stroke mortality rates have declined fairly steadily in all regions of the United States and for all race/sex groups, although the rates of decline were greater during 1970 to 1978 than during 1979 to 1989. The declines in underlying-cause rates could not be attributed to a shift toward reporting stroke as a contributing rather than underlying cause of death, since both underlying- and multiple-cause rates declined similarly. There was significant regional variation in the rate of decline, particularly during 1979 to 1989. The South initially had the highest rates, but it experienced the most rapid decline, so that by 1989 the South no longer had the highest rates. States with the most rapid rates of decline were significantly clustered in the South and particularly the Southeast. Most of the decline in overall stroke mortality was due to declines in ischemic stroke mortality.

CONCLUSIONS

During 1970 to 1989 there was significant geographic variation in the rate of decline of stroke mortality rates, with the most rapid rates of decline concentrated in the high-rate areas of the South and particularly the Southeast. As a result, there has been a decrease in interregional and interstate variation in stroke mortality rates, which is apparently not due to an artifact of changing reporting patterns.

Effects of interstate migration on the geographic distribution of stroke mortality in the United States

BACKGROUND AND PURPOSE

This study examines the effects of lifetime net interstate migration on the geographic distribution of stroke mortality in the United States.

METHODS

National Center for Health Statistics and Bureau of the Census data were used to map the geographic distribution of age-adjusted, race-, and race/sex-specific stroke mortality rates by interstate migration status for natives, outmigrants, nonmigrants, inmigrants, and residents in the United States for 1979 to 1981.

RESULTS

High age-adjusted stroke mortality rates were significantly clustered in the southeastern United States for both whites and blacks; in addition, for whites, low-rate states were concentrated in some Mountain and northeastern states. Migrant status did not change this large-scale pattern, but individual states showed significant migration effects, which varied in magnitude and direction. Among whites, states that benefited from migration, with markedly lower stroke mortality rates among residents than natives, included Arizona, Colorado, District of Columbia, and Florida, whereas states that suffered from migration included California, Idaho, Montana, North Dakota, Nevada, and Oklahoma. Among blacks, only Colorado showed an apparent large benefit from migration, whereas 21 states suffered from migration.

CONCLUSIONS

Although the overall large-scale spatial distribution of resident stroke mortality rates cannot be explained by migration effects, some individual states had rates that were strongly influenced by migration. Patterns of mortality among migrant groups in Sun Belt retirement destination states probably result from differential selection effects for retirement migration in older adults. Patterns of mortality for black migrants to the North are probably influenced by "carryover" effects from their origin states.

Coronary and cerebrovascular atherosclerosis: two aspects of the same disease or two different pathologies?

Cerebrovascular and coronary disease are characterized by some common aspects. Indeed the same risk factors relate to coronary heart disease and to cerebrovascular disease. However, there may be differences in the pathogenesis of atherosclerotic lesions in coronary and cerebral arteries. In fact some populations are characterized by a high incidence of ischaemic stroke and a low incidence of myocardial infarction, while in other populations there is an opposite trend. These differences could be explained on the basis of: genetic risk factors; a different prevalence of risk factors; a different reactivity of the coronary and cerebral arteries to risk factors; anatomical differences concerning coronary and extracranial cerebral arteries with respect to intracranial cerebral arteries. Atherosclerosis is undoubtedly a systemic disorder and its genetic and environmental causal factors are only partly known. The variable incidence of cerebrovascular and coronary heart disease in the same population or in different populations as well as the different nature of atherosclerotic plaques are probably related to the different prevalence of the causal factors, even though these may not always be identified.

Heart disease deaths in a Japanese urban area evaluated by clinical and police records

BACKGROUND

By national statistics, Japanese ischemic heart disease (IHD) mortality is one of the lowest of all industrialized countries, and the proportion of deaths due to heart failure in heart disease is the highest. There may be a difference in diagnostic preference between Japan and other industrialized countries.

METHODS AND RESULTS

IHD deaths according to the death certificates were reevaluated with World Health Organization MONICA criteria for those 25 to 74 years old by use of clinical and police records in a Japanese city with a population of 347,000. Their cause of death was given on the death certificates as IHD (International Classification of Diseases [ICD], ninth revision, codes 410-414), heart failure (428), or other heart diseases (393-405, 415-427, 429) in 1984 through 1986. Some deaths in 1985 through 1986 from stroke (430-438) or other diseases (250, 272, 278, 440-448, 797-799) were added. Of 409 subjects, 397 (97%) could be examined. Reevaluation of the 106 deaths originally diagnosed as IHD yielded 73 IHDs and 11 sudden deaths of unknown origin (SD), and reevaluation of 160 deaths originally called heart failure yielded 26 IHDs and 50 SDs. In total, reevaluation of all 397 deaths yielded 101 IHDs and 69 SDs. Some 88% of SD cases were originally certified as heart failure (72%) or IHD (16%). Only two SDs were originally certified as stroke.

CONCLUSIONS

Assuming that 30% of SDs were due to IHD, the number of IHD deaths would be 122, which is 11% larger than the number of IHD deaths according to the death certificates. After reevaluation, the IHD mortality in this study area still was the lowest in the industrialized countries.

Reliability of death certificate diagnoses

Consistency between death certificates and clinical records from 5 general hospitals in Kuwait was studied for 470 deaths with the following underlying or associated causes: hypertensive (HYP), ischaemic heart diseases (IHD), cerebrovascular diseases (CVD) and diabetes mellitus (DM). Direct causes were not considered since they are of little interest analytically. Only deaths with definite or most probable ascertainment were included. One cardiologist, who was provided with the WHO criteria and relevant documents on death certification, independently reviewed the records. To test the reviewer's bias and the reliability of his judgement, an adjudication process was effected by having one senior cardiologist re-review a random subsample of 140 records. The two reviewers showed good agreement. Specific diagnoses criteria for deciding the underlying cause of death in multiple morbid conditions by the reviewer were followed. Due to possible reviewer bias, we aimed at measuring the difference between initial certifiers and the reviewer rather than measuring the diagnostic accuracy of initial certifiers in reference to the reviewer. The agreement index kappa showed poor agreement between original and revised certificates. The original certificates under-estimated CVD as an underlying cause of death by 69.2%, DM by 60%, IHD by 33.5% and HYP by 31.8% in our sample. Associated causes were also consistently under-estimated by initial certifiers as compared with the reviewer. This bias calls for basing mortality statistics in Kuwait on hospital death committees' reports rather than on initial certifier death certificates, use of multiple-causes of death instead of one underlying cause and adequate training of the medical profession on the value and process of death certification.

Trends in the geographic inequality of cardiovascular disease mortality in the United States, 1962-1982

Substantial geographic variation of cardiovascular disease (CVD) mortality within the U.S. has been recognized for decades. Analyses reported here address the question of whether relative geographic inequality has increased or decreased during the period of rapidly declining CVD mortality 1962-1982. Trends in geographic inequality, as measured by the weighted coefficient of variation of State Economic Area rates, are analyzed for whites and blacks by sex for 10-year age groups 35-44 to 85 and over. The average annual percent change in the coefficient of variation for each demographic group is presented for all cause mortality, all CVD, stroke and ischemic heart disease. In general, geographic inequalities declined in total mortality for all except the youngest age group. This is consistent with reports of a strong convergence of age-adjusted cancer mortality in U.S. counties. By contrast, increasing geographic inequality dominates in the CVD categories, especially for whites in heart disease and stroke. At younger ages, increases in the coefficient of variation for all race-sex groups exceeded 1% per year in stroke and 2% per year in heart disease. These results suggest that factors influencing the percent decline of CVD mortality are not reaching communities of the U.S. equally. Since increases in relative inequality are strongest in the younger age groups, the pattern of inequality may be accentuated as these cohorts move into ages of higher mortality.

CVD mortality, 1968-1978: observations and implications

U.S. multiple cause of death data were examined for the period 1968-1978. Specifically, the role of cerebrovascular disease mortality as an underlying and associated cause of death was studied. The number of deaths where cerebrovascular disease was cited as the underlying cause of death declined much faster than the number of deaths where cerebrovascular disease was cited as the associated cause of death. This trend is indicative of a possible change in the role of cerebrovascular disease as an associated cause of death. Cause elimination life tables were constructed for cerebrovascular disease as the underlying cause of death and as any cause of death. In the general population, eliminating stroke as a cause of death is projected to have less impact in 1978 than in 1968, for men than for women, and for whites than for nonwhites. Tables were also constructed to examine the life expectancy gains for the group of individuals who died of cerebrovascular disease. For these individuals, the gain in life expectancy at birth ranges from 9 years for white males to 18 years for nonwhite females.

Stroke in south Alabama: incidence and diagnostic features--a population based study

This study has attempted to identify all persons from an area of southern Alabama who had a stroke in 1980 and were hospitalized. Data were gathered on disease onset, clinical course, laboratory results, history of risk factors, and outcome. The age-adjusted incidence rates for initial stroke were 109 per 100,000 for whites and 208 per 100,000 for blacks. Age-specific rates were higher in blacks than whites, and highest for black females. The distribution of cases by type of stroke was: atherothrombotic (6%), embolic (26%), lacunar (13%), infarction of unspecified origin (40%), parenchymatous hemorrhage (8%), subarachnoid hemorrhage (6%), and unidentified type (1%). Blacks had higher incidence rates for hemorrhages, and black females had the highest incidence rate for lacunar stroke. The overall stroke incidence rates in this series were not significantly higher than those from prior population studies, suggesting that southern Alabama is not part of the so-called "Stroke Belt" area of the southeastern United States.

Trends in mortality from cerebrovascular diseases in the United States, 1960 to 1975

A long-term decline in death rates from cerebrovascular diseases in the United States accelerated in 1969, with a further increase in the rate of decline after 1972. This break in the pattern of the mortality curve for stroke was observed in all 4 major sex-color groups, and affected all age groups in which a significant number of stroke deaths occur. The decline for non-whites was relatively and absolutely greater than for the comparable white sex. If the 1960 rates had persisted in 1975, 87,600 more lives would have been lost to cerebrovascular diseases. Although there are no data documenting a declining prevalence of hypertension in the population, detection, treatment and control of hypertension have improved markedly over recent years. A concomitant decrease in the severity of epidemic respiratory infection may have contributed to the improvement in recorded death rates from stroke. Mortality from all major cardiovascular diseases has demonstrated a parallel downward trend. Continued emphasis on public health efforts to detect and treat hypertension and other known cardiovascular risk factors can be expected to result in further improvement in cardiovascular mortality.

Three-area epidemiological study of geographic differences in stroke mortality. I. Background and methods

An epidemiological study was conducted to determine the geographical variations in stroke mortality among three U.S. areas. They were Savannah, Georgia (high stroke rates), Hagerstown, Maryland (intermediate stroke rates) and Pueblo, Colorado (low stroke rates). In each area samples were drawn of the population in the 35--54 age group. The subjects were interviewed and examined to obtain the information required on medical conditions and/or living habits which would characterize each area. A brief medical and family history, as well as demographic and personal data, were obtained by interview. The medical examination included blood pressure, ECG, blood and urine chemistry, height and weight. In all three cities the response rate in the final sample selected was 90% (2,375 individuals) interviewed and 74% (1.939 individuals) examined.

Comparison of hospital admissions for cerebrovascular disease in Michigan and North Carolina

Hospital admission rates and death rates for cerebrovascular disease differ markedly between states. Hospital admission data were analyzed: (a) to ascertain why death rates from this disease group are lower in Michigan than in North Carolina and (b) to clarify whether hospital care in either state has inadequacies that can be corrected quickly. Among both whites and blacks of the same age, case-fatality ratios were higher in North Carolina than in Michigan. Subarachnoid and cerebral hemorrhages were diagnosed more often in the southern state. For both areas, the records showed a marked underreporting of hypertension and diabetes mellitus as secondary conditions in the hospital admissions; elevated blood pressures were about equally common in each state but were treated more vigorously in Michigan. Secondary diagnoses of respiratory disease and use of anti-infective agents were reported more frequently in North Carolina. In contrast, diabetes mellitus was more prevalent in Michigan admissions. Some reasons for these findings are advanced, particularly as they relate to diagnostic and treatment patterns. Finally, the need for more detailed research is emphasized to create guidelines for better hospital care of cerebrovascular disease.

Geographic differences in mortality from stroke in North Caroline. 1. Analysis of death certificates

Analysis of death certification in North Carolina for a three-year period, 1969 through 1971, showed regional differences in mortality rates from stroke in white men, with the highest rates in the Plains (tobacco growing and farming) area and the lowest rates in the Mountain region. These geographic differences in death rates were observed in all but the youngest age decade and also in the various types of stroke, i.e., hemorrhagic and occlusive cerebrovascular diseases. This regional variation in mortality, however, was not present in white women or blacks. The prevalence at death of heart disease, hypertension and diabetes also was higher in the Plains than in the Mountain region, suggesting that the observed geographic variation of stroke mortality is related to one or more of these major risk factors. It is concluded that the geographic differences in stroke mortality, which had been reported during previous decades, are real and are not due to variations in death certification, errors in diagnosis, or other explanations that might artificially produce inaccuracies in vital statistics.

Nationwide cerebrovascular disease morbidity study

Previous studies have noted that the geographic differences in stroke mortality among areas of the United States were not due to artifacts of certification practices or accuracy of the diagnosis. A study of hospitalized stroke patients was completed in order to determine whether the mortality differences were due to a higher incidence or case fatality following a stroke in areas with high stroke death rates. Eight of the nine areas that participated in the Nationwide Mortality Study were included in this study. A total of 2,619 stroke cases were ascertained including 1,631 (62.3%) who were alive at the time of hospital discharge, 937 (35.8%) dead at discharge, 46 (1.7%) who were discharged alive but died outside of the hospital, and five (0.2%) who were dead at discharge and certified by the medical examiner.

The incidence of stroke was higher in the high stroke death rate areas especially for men. The ratio of the incidence of stroke in men as compared to women was higher in the younger age groups (45–54, 55–64) and in the high-incidence as compared to low-incidence areas.

The case-fatality percentage was lowest in Denver and highest in South Carolina. Presence of coma on admission was the principal determinant of subsequent mortality in all areas.

Finally, there was no consistent difference in the distribution of symptoms of stroke among the areas, and diagnostic procedures were performed more often in urban than rural areas. Approximately 80% of the stroke cases could be substantiated by either an autopsy verifying diagnosis, arteriography, hemorrhagic spinal fluid, hemiplegia or coma on admission. Several hypotheses to explain the differences have been suggested as well as the need for new information.