The long-term monitoring of cardiovascular disease: is it feasible?

The Sino-MONICA-Beijing Study: report on results between 1984 and 1986

The Beijing Heart Lung and Blood Vessel Medical Center has participated in the World Health Organisation MONICA project since 1981. Our study, named Sino-MONICA-Beijing, has been carried out in Beijing and covers a population approximately of 700,000. After a 2-year pilot study, the project started formally January 1, 1984. This paper presents the organization and methodology of the study, with emphasis on the monitoring system and on how events were found. The main results of the cardiovascular disease (CVD) event monitoring are as follows: average annual mortality from all causes, for the 3-year period of 1984-86 was 319/100,000 for men and 238/100,000 for women aged 25-64; from CVD 119/100,000 for men and 101/100,000 for women; from ischemic heart disease 29/100,000 for men and 14/100,000 for women; and from cerebrovascular disease 59/100,000 for men and 52/100,000 for women. Preliminary experience has shown that Sino-MONICA-Beijing is a well-standardized project of long-term surveillance of CVD in the communities of Beijing.

Incidence, comorbidity, case fatality and readmission of hospitalized stroke patients in Canada

BACKGROUND

Stroke is a leading cause of death and disability, and poses a significant burden of care for those who survive.

OBJECTIVES

To estimate the incidence of hospitalization for stroke and describe the impact of age, sex and comorbidity on in-hospital mortality, length of stay and readmission rates.

METHODS

Health insurance numbers were used to link acute care hospitalizations across Canada in 1999/2000 for stroke patients with no discharges for a stroke within the preceding five years. Patients were followed up for one year from the date of their initial admission.

RESULTS

The numbers of men (15,367) and women (16,740) in the study were similar. The incidence of all types of stroke (International Classification of Diseases, ninth revision, codes 430, 431 and 434/436) for hospitalized men and women was 14.4 per 10,000, with a 15-fold rise from 8.7 for the age group of 45 to 64 years to 131.9 per 10,000 for the age group 80 years and older. For the index episode, stroke patients spent an average of 21.0 days in the hospital, and 18.2% died in the hospital within 28 days. Of those who survived the first episode, 10.3% were readmitted to the hospital within one year with a recurrent stroke, and overall 37.1% were readmitted for any cause (including stroke). Among these stroke patients, hypertension was codiagnosed in 35%; diabetes in 17%; arrhythmia in 15%; ischemic heart disease in 13.6%; and congestive heart failure in 5%.

CONCLUSIONS

Hospital records linked by patient identification can produce more accurate national estimates of patients hospitalized with stroke than any current countrywide surveillance system.

Helicobacter pylori, Chlamydia pneumoniae and myocardial infarction

BACKGROUND

Several epidemiological studies have suggested a positive association of coronary heart disease with both Helicobacter pylori and Chlamydia pneumoniae infection. The issue has been difficult to resolve because of the potential impact of several confounding factors, in particular, socioeconomic status for H. pylori and smoking for C. pneumoniae.

METHODS

A case-control study was carried out of 341 patients with a recent myocardial infarction (MI) and 831 community controls who had serology tests for H. pylori and C. pneumoniae (selected from a total study number of 1745 subjects). Individuals of Pacific Island or Maori ethnicity were excluded because they were infrequent.

RESULTS

H. pylori seropositivity was associated with increasing age (P < 0.001) and lower household income (P = 0.0003) but not with gender, smoking status or alcohol intake. H. pylori was associated with lower high-density lipoprotein cholesterol (P = 0.007) and a higher body mass index (P = 0.007). The overall seropositivity for H. pylori was 41.6% for patients with MI and 34.5% for age and sex-matched population controls. The odds ratio was 1.34 (95% confidence interval (CI): 1.00-1.80; P = 0.038) after adjusting for age and sex. C. pneumoniae seropositivity was significantly associated with male sex, younger age (P = 0.03) and smoking status (P = 0.004) but not associated with household income or any other measured risk factor for coronary heart disease. The overall seropositivity for C. pneumoniae was 51.2% for patients with recent MI and 43.5% for controls. After adjusting for age and sex, the odds ratio was 1.24 (95%CI: 0.95-1.62; P = 0.11). Subgroup analysis showed no clear pattern within different age groups. In particular, the odds ratio for H. pylori seropositivity in younger subjects (aged 35-49 years) was similar to the overall group (1.38; 95%CI: 0.83-2.29).

CONCLUSION

The association between H. pylori or C. pneumoniae seropositivity and coronary heart disease was significant but may not indicate a causal association.

Incidence of the major stroke subtypes: initial findings from the North East Melbourne stroke incidence study (NEMESIS)

BACKGROUND AND PURPOSE

Population-based stroke incidence studies are the only accurate way to determine the number of strokes that occur in a given society. Because the major stroke subtypes have different patterns of incidence and outcome, information on the natural history of stroke subtypes is essential. The purpose of the present study was to determine the incidence and case-fatality rate of the major stroke subtypes in a geographically defined region of Melbourne, Australia.

METHODS

All suspected strokes that occurred among 133 816 residents of suburbs north and east of Melbourne, Australia, during a 12-month period of 1996 and 1997 were identified and assessed. Multiple overlapping sources were used to ascertain cases, and standard criteria for stroke and case-fatality were used. Stroke subtypes were defined by CT, MRI, and autopsy.

RESULTS

Three hundred eighty-one strokes occurred among 353 persons during the study period, with 276 (72%) being first-ever-in-a-lifetime strokes. Of these, 72.5% (95% CI 67.2% to 77.7%) were cerebral infarction, 14.5% (95% CI 10.3% to 18.6%) were intracerebral hemorrhage, 4.3% (95% CI 1.9% to 6.8%) were subarachnoid hemorrhage, and 8.7% (95% CI 5.4% to 12.0%) were stroke of undetermined type. The 28-day case-fatality rate was 12% (95% CI 7% to 16%) for cerebral infarction, 45% (95% CI 30% to 60%) for intracerebral hemorrhage, 50% (95% CI 22% to 78%) for subarachnoid hemorrhage, and 38% (95% CI 18% to 57%) for stroke of undetermined type.

CONCLUSIONS

The overall distribution of stroke subtypes and 28-day case-fatality rates are not significantly different from those of most European countries or the United States. There may, however, be some differences in the incidence of subtypes within Australia.

Stroke incidence on the east coast of Australia: the North East Melbourne Stroke Incidence Study (NEMESIS)

BACKGROUND AND PURPOSE

Community-based stroke incidence studies are the most accurate way of explaining mortality trends and developing public health policy. The purpose of this study was to determine the incidence of stroke in a geographically defined region of Melbourne, Australia.

METHODS

All suspected strokes occurring in a population of 133 816 residents in suburbs north and east of Melbourne, Australia, during a 12-month period of 1996 and 1997 were found and assessed. Multiple overlapping sources were used to ascertain cases, and standard definitions and criteria for stroke and case fatality were used.

RESULTS

A total of 381 strokes occurred among 353 people during the study period, 276 (72%) of which were first-ever-in-a-lifetime strokes. The crude annual incidence rate (first-ever strokes) was 206 (95% CI, 182 to 231) per 100 000 per year overall, 195 (95% CI, 161 to 229) for males, and 217 (95% CI, 182 to 252) for females. The corresponding rates adjusted to the "world" population were 100 (95% CI, 80 to 119) overall, 113 (95% CI, 92 to 134) for males, and 89 (95% CI, 70 to 107) for females. The 28-day case fatality rate for first-ever strokes was 20% (95% CI, 16% to 25%).

CONCLUSIONS

The incidence rate of stroke in our population-based study is similar to that of many European studies but is significantly higher than that observed on the west coast of Australia.

Ethnic differences in coronary heart disease case fatality rates in Auckland

Data from the Auckland Coronary or Stroke (ARCOS) study for the years 1983 to 1992 were analysed to describe 28-day case fatality rates from coronary heart disease among Europeans, Maori and Pacific Islands people in Auckland, New Zealand. The case fatality rate was consistently higher in each age group and for both sexes among Maori and Pacific Islands people than in Europeans. Age-standardised case fatalities for Maori and Pacific Islands people were similar at around 65 per cent, compared with around 45 per cent among Europeans, and these differences were not explained by ethnic differences in possible underreporting of nonfatal myocardial infarction, in socioeconomic status, smoking, symptoms or past myocardial infarction. There was evidence of a more rapid progression of acute coronary events to a fatal outcome among Maori and Pacific Islands people, partly explained by delays in access to life support and coronary care: greater proportions of Pacific Islands people than Maori or Europeans who died did so within an hour of onset of symptoms (56 per cent of Pacific Islands people, 47 per cent of Maori, 45 per cent of Europeans). Pacific Islands and Maori people with acute coronary events took longer to reach a coronary care unit (mean times: Pacific Islands people 8.6 hours, Maori 7.4 hours, Europeans 6.7 hours, P < 0.05), although the median times were not significantly different; life-support units were used by a majority of Pacific Islands people and Europeans (57 per cent and 55 per cent, respectively), compared with only 46 per cent of Maori, but hospital care was similar for the three groups. Further qualitative and quantitative research is needed to investigate the reasons for these ethnic disparities in case fatality rates.

Prevalence of stroke and stroke-related disability. Estimates from the Auckland stroke studies

BACKGROUND AND PURPOSE

To provide estimates of the prevalence of stroke and stroke-related disability for international comparisons and for planning purposes.

METHODS

Estimates of prevalence were derived from two population-based studies conducted 10 years apart in Auckland, New Zealand. The first, carried out in 1981, included information on survival and stroke-related disability to 14 years after stroke, and the second, undertaken in 1991 to 1992, included this information up to 3 years after stroke. An actuarial model was developed that took into account changes in incidence, long-term survival, and population structure.

RESULTS

Overall, it was estimated that 7491 people (3793 men and 3698 women) living in Auckland (total population 945,000) in 1991 had experienced a stroke at some stage in the past. This represents an age-standardized rate of 833 per 100,000 (991 per 100,000 in men and 706 per 100,000 in women) in the population aged 15 years and older. When only those who have made an incomplete recovery are considered, prevalence falls to 461 per 100,000. Of this group, one third (173 per 100,000 population 15 years and older) required assistance in at least one self-care activity.

CONCLUSIONS

Usual estimates of stroke prevalence, which include all people who have ever experienced a stroke, may overestimate by almost twofold the prevalence of stroke-related disability, since many have either recovered or have no continuing dependency related to stroke. Overall prevalence does not provide information with sufficient precision for planning and purchasing ongoing services for stroke patients.

Comparable studies of the incidence of stroke and its pathological types: results from an international collaboration. International Stroke Incidence Collaboration

BACKGROUND AND PURPOSE

Comparing stroke rates in different parts of the world may increase our understanding of both etiology and prevention. However, comparisons are meaningful only if studies use standard definitions and methods, with comparably presented data. We compared the incidence of stroke and its pathological types (cerebral infarction, primary intracerebral hemorrhage, and subarachnoid hemorrhage) in recent studies from around the world.

METHODS

Studies with a midyear of 1984 or later, fulfilling standard criteria for a comparable, community-based study, provided original data for comparative analyses.

RESULTS

By mid-1995, data were available from 11 studies in Europe, Russia, Australasia, and the United States, comprising approximately 3.5 million person-years and 5575 incident strokes. Age- and sex-standardized annual incidence rates for subjects aged 45 to 84 years were similar (between approximately 300/100,000) and 500/100,000) in most places but were significantly lower in Dijon, France (238/100,000), and higher in Novosibirsk, Russia (627/100,000). In subjects aged 75 to 84 years, however, Novosibirsk no longer ranked higher than the other studies. The distribution of pathological types, when these were reliably distinguished, did not differ significantly between studies.

CONCLUSIONS

The similarities in stroke incidence and pathological types are perhaps not surprising given that all the populations were westernized and mainly white. The higher rates in Novosibirsk, disappearing in the elderly, and the lower rates in Dijon have several potential explanations. These include methodological artifact and different patterns of population risk factors. Further work is needed to explore these possibilities and to extend our knowledge of stroke incidence to other parts of the world, especially developing countries.

Comparing stroke incidence worldwide: what makes studies comparable?

BACKGROUND

Comparing stroke rates in different parts of the world and at different points in time may increase our understanding of the disease. Comparisons are only meaningful if they are based on studies that use similar definitions, methods, and data presentation.

SUMMARY OF REVIEW

We discuss the criteria that make such studies comparable, drawing on the experiences of recent studies performed around the world. If only those studies that fulfill the proposed criteria for comparison are considered, comparable data do not exist for vast areas of the world, including Africa, Asia, and South America. The importance of complete, community-based case ascertainment, including strokes managed outside the hospital, is emphasized. An approach for measuring and comparing the incidence of the pathological types of stroke (cerebral infarction, primary intracerebral hemorrhage, and subarachnoid hemorrhage) and subtypes of cerebral infarction is suggested.

CONCLUSIONS

The "ideal" stroke incidence study does not exist, but studies closely approaching it will reveal the most reliable and comparable results. There is a need for further studies to fill the gaps in our knowledge of the worldwide incidence of stroke, particularly for developing countries.

Community surveillance of coronary heart disease in the Atherosclerosis Risk in Communities (ARIC) Study: methods and initial two years' experience

The community surveillance component of the Atherosclerosis Risk in Communities (ARIC) Study is designed to estimate patterns and trends of coronary heart disease (CHD) incidence, case fatality, and mortality in four U.S. communities. Community surveillance involves ongoing review of death certificates and hospital discharge records to identify CHD events in community residents aged 35-74 years. Interviews with next of kin and questionnaires completed by physicians and medical examiners or coroners were used to collect information on deaths, and review and abstraction of hospital records were used to collect information on possible fatal and nonfatal myocardial infarctions (MIs). Events were classified using standardized criteria. The initial 2-years' experience with case ascertainment and availability of information needed for classification of events is described. Average annual age-adjusted attack rates of definite MI and CHD mortality rates for blacks in two communities and whites in the four communities are presented and compared with rates based on unvalidated hospital discharge data and vital statistics. Age-adjusted rates based on ARIC classification of definite MI were lower than those based on hospital discharge diagnosis code 410 (e.g., 5.60/1000 and 11.50/1000 among Forsyth County white men, respectively). Age-adjusted rates of definite fatal CHD based on ARIC classification were similarly lower than rates based on underlying cause of death code 410; for example, Jackson black men had rates of 2.82/1000 and 4.52/1000 for definite fatal CHD and UCOD 410-414 or 429.2, respectively.

Changes in stroke incidence and case-fatality in Auckland, New Zealand, 1981-91

The explanation for the substantial decline in stroke death rates can be investigated only by measuring trends in stroke incidence and case-fatality. Two community-based studies carried out in Auckland, New Zealand, in 1981 and 1991 used comparable methods and definitions, met criteria for well-designed studies, and had the power to detect small changes in incidence and case-fatality rates. 703 events (representing 50% of all strokes) were registered in 1981 and 1735 events in 1991. 521 (74.1%) and 1255 (72.3%) events in 1981 and 1991, respectively, were first-ever (in a lifetime) strokes. Although there was no change in overall stroke incidence between 1981 and 1991, there were changes in age and sex groups. The incidence rate among women younger than 75 years rose by a fifth (rate ratio 1.23 [95% CI 1.04-1.47]), whereas that in men of 75 years and older fell by a third (rate ratio 0.67 [0.54-0.82]). The 28-day case-fatality declined from 27.1 (21.7-32.6)% to 21.9 (18.1-25.7)% in men and from 37.6 (31.8-43.5)% to 25.8 (22.3-29.4)% in women from 1981 to 1991, but the decline was not statistically significant in any age or sex group. These findings suggest that we need to reappraise strategies for the prevention of stroke and assess the implications of improved survival in elderly stroke patients.

Stroke trends in Australia and New Zealand: mortality, morbidity, and risk factors

Stroke death rates are declining in Australia and New Zealand as in many other industrialized countries. An explanation for the decline in mortality requires information from population-based incidence studies. Two studies that meet the criteria for well-designed stroke studies have been conducted, one in Auckland, New Zealand, in 1991 and the other in Perth, Western Australia, in 1988 to 1989. Comparisons between the two studies reveal similar incidence and case-fatality rates for both men and women, reflecting the similar mortality rates. The Auckland study repeats one carried out 10 years earlier and allows an insight into the changes in incidence, case fatality, and severity of stroke in a large urban population. Between the two study periods there was no overall change in the incidence rates but case-fatality rates improved in both men and women. Although there have been significant improvements in the level of smoking in both Australia and New Zealand during the 1980s, only marginal improvements in mean population blood pressure have occurred, despite efforts and resources directed at identification of individuals with raised blood pressure. This high-risk strategy has apparently had only a very limited impact on reducing the incidence of stroke in the population.

Alcohol consumption and risk of coronary heart disease

OBJECTIVE

To investigate the hypothesis that the apparent protective effect of habitual alcohol consumption on coronary heart disease is due to drinkers at high risk of coronary heart disease becoming non-drinkers.

DESIGN

Case-control population based study. Data were obtained from interviews with patients with non-fatal myocardial infarction and their controls and with the next of kin of those who had died of coronary heart disease and their controls.

SETTING

Auckland, New Zealand.

SUBJECTS

Two groups of cases were studied. The first comprised 227 men and 72 women with non-fatal myocardial infarction identified from a population based surveillance programme for coronary heart disease; controls were 525 men and 341 women randomly selected from the same population group and matched for age and sex. The second group comprised 128 men and 30 women who had died of coronary heart disease and had been identified from the surveillance programme; controls were a sample of the previous control group and comprised 330 men and 214 women matched for age and sex. All participants were aged 25-64 years and without diagnosed coronary heart disease.

MAIN OUTCOME MEASURES

Regular alcohol consumption; high density lipoprotein cholesterol and low density lipoprotein concentrations.

RESULTS

Men with myocardial infarction and men who had died of coronary heart disease were more likely to have been never drinkers (had never drunk more than once a month) than controls (18% v 12% and 23% v 13% respectively). After possible confounding factors had been controlled for, people in all categories of drinking (up to more than 56 drinks per week) had at least a 40% reduction in risk of fatal and non-fatal coronary heart disease compared with never drinkers. Former drinkers also had a lower risk of non-fatal myocardial infarction than never drinkers (relative risks 0.41 and 0.10 in men and women respectively) but a similar risk of death from coronary heart disease. The reduction in risk was consistently greater in women than in men in all drinking categories but there was no clear dose-response effect in either sex.

CONCLUSIONS

The results support the hypothesis that light and moderate alcohol consumption reduces the risk of coronary heart disease. This protective effect in this population was not due to the misclassification of former drinkers with a high risk of coronary heart disease as non-drinkers.

Predicting survival after stroke: a three-year follow-up

We examined characteristics associated with a high risk of mortality within 3 years after a stroke. Analyses are based on data from a population-based register of stroke events that occurred in Auckland (total population 829,545), New Zealand during a 1-year period in 1981-1982 and a 3-year follow-up study of all survivors (97% complete). Statistical techniques that allow for the simultaneous evaluation of multiple factors indicated that retention of consciousness, decreasing age, and place of residence at the onset of the stroke were the strongest predictors of survival over 3 years. The survival rate for those living at home at the onset of the stroke who did not lose consciousness was 58% compared with 5% for people in institutional care who lost consciousness. Marital status, history of stroke, and ethnic group also predicted survival. Most of the important prognostic factors we identified in our study cannot be modified, testifying to the importance of the prevention of stroke in the first place.

Validation of coronary heart disease hospital discharge data

Data from a 1983 Auckland coronary heart disease register applying current World Health Organization criteria have been used to validate routine hospital discharge data. The register contained 905 patients under 65 years admitted to hospital and 858 of these patients were matched with hospital discharge records. Of the registered definite myocardial infarction cases 86% received the International Classification of Diseases code 410 (acute myocardial infarction); 9% of these cases received a code 411-414 (other forms of coronary heart disease or angina) and 5% received other codes. Only 405 of the 604 cases (67%) coded 410 in the hospital discharge data were true definite myocardial infarctions according to the World Health Organization criteria. The routine hospital International Classification of Diseases data do not provide diagnostic groups sufficiently close to World Health Organization categories for them to be used alone to monitor trends in coronary heart disease morbidity rates.

Cigarette smoking and risk of premature stroke in men and women

A case-control study was carried out of the relation between cigarette smoking and hypertension and stroke. A total of 132 cases of stroke (79 in men, 53 in women) identified as a part of a population based register were compared with 1586 controls (1017 men, 569 women) from a survey of cardiovascular risk factors conducted in the same population. Cigarette smokers had a threefold increase in the risk of stroke compared with current non-smokers. This association remained significant after adjusting for hypertension. Those who both smoked and had hypertension had an increased risk of stroke of almost 20-fold compared with those who neither smoked nor had hypertension. Overall, in this population roughly 37% of stroke events may be attributed to cigarette smoking and 36% to hypertension.

The problem of home management in the estimation of the incidence of acute myocardial infarction from hospital records

Past studies of the incidence of acute myocardial infarction (AMI) have found information for patients managed at home difficult and expensive to obtain. This study attempted to find whether the efficiency of gathering this information could be improved, or if this group of patients could be neglected entirely. A random sample of 270 doctors in Perth were asked about their management of cases of suspected AMI at home. Of these doctors, 78% said that they never managed AMI at home; excluding such doctors before seeking voluntary notification of new cases managed at home could make population surveys of AMI more efficient. For patients under 65 it was estimated that about 1% or less of non-fatal cases meeting World Health Organization criteria for definite AMI were managed at home. Thus neglecting this group would probably cause little bias in computing incidence rates for AMI in Perth.

Subarachnoid hemorrhage: epidemiology, diagnosis, management, and outcome

A population-based study of primary subarachnoid hemorrhage in Auckland (population 829,454), New Zealand, identified 180 cases in a two-year period. This represented an age adjusted incidence rate of 10.5 and 18.3 per 100,000 for men and women respectively. Sixty-eight percent of all cases had a proven intracranial aneurysm or arteriovenous malformation, 15% had negative angiographic findings and in the remaining 17%, the presence or absence of a localized lesion was unknown since neither angiography nor autopsy were performed. Twenty-six patients (15%) died before hospitalization and a further 36 patients (20%) died within 48 hours of onset. Only 94 patients (53% of all patients registered) were fit enough to undergo angiography. A surgical operation was carried out on 60 of the 68 patients in whom an aneurysm was confirmed at angiography. The overall case fatality rate was 36% within the first 48 hours, 43% in the first week and 57% at both six months and one year. The high early case fatality rates are similar to those found in previous population-based studies, suggesting that despite the major advances to individual patients from technological advances, the potential contribution of hospital management to the reduction of subarachnoid haemorrhage mortality rates is likely to be limited.

Trends in survival after myocardial infarction in New Zealand, 1974-81

Coronary heart disease mortality in New Zealand has declined by 20% in the 13 years since 1968. One possible explanation for this decline is lower case-fatality rates resulting from improvements in the management of myocardial infarction. This paper tests this hypothesis by examining trends in 1-year survival following a definite myocardial infarction for the population aged 35-69 in Auckland. The data were obtained from two methodologically identical population-based registers of myocardial infarction compiled in 1974 and 1981 in Auckland. In both periods the 1-year crude case-fatality rate was 30% and the pattern of survival over 1 year was similar. These data suggest that factors other than the improved care of myocardial infarction patients are responsible for the decline in coronary heart disease mortality rates in New Zealand.