Changing patterns of medical treatment in acute myocardial infarction

TYPE OF STUDY

Descriptive study of trends in the drug therapy for acute myocardial infarction.

SETTING

Population-based register of acute coronary events compiled for the years 1984 to 1990 in the course of the Perth MONICA project.

CASES

5294 cases meeting clinical criteria for acute myocardial infarction.

RESULTS

Striking changes were seen in the use of aspirin before admission to hospital (from 4% to 18%). During the stay in hospital the use of beta-blockers increased steadily from 52% to 76%, while the use of aspirin increased 3.5-fold from 25% to 88% and the use of streptokinase increased 13.5-fold from 2.4% to 32.4%. The proportion of patients prescribed beta-blockers on discharge from hospital increased from 46% to 65% and that for aspirin rose from 16% to 83%. There were also major relative increases in the use of lipid-lowering agents and declines in the use of antiarrhythmic drugs.

CONCLUSION

These trends in the pharmacological management of myocardial infarction mirror the emerging evidence from clinical trials, although the increases in the use of certain types of drugs antedated publication of the results of major randomised studies. The changes in therapy would partly explain observed improvements in case fatality and may have contributed to the decline in coronary mortality observed in the Perth community.

Follow‐up care after acute myocardial infarction

OBJECTIVE

To examine the medical care received by patients following discharge from hospital after acute myocardial infarction (AMI).

SETTING AND DESIGN

Community-based cross-sectional survey.

PATIENTS

2836 consecutive patients aged 25-64 years living in the Perth Statistical Division who were admitted to hospital with AMI during 1984-1988. After one reminder the response rate was 71%.

RESULTS

Half of all respondents were in full-time employment at the time of their AMI. At follow-up this had fallen to a third. Over 80% of patients visited a cardiologist after AMI, with half remaining under consultant care to the time of survey. However, one in five patients reported no follow-up care at the time of survey. Seventy-three per cent of patients reported undergoing at least one exercise stress test after AMI, with 61% undergoing angiography, 16% angioplasty and 24% coronary bypass surgery. Large proportions of the patients accurately reported being prescribed beta-blockers and antiplatelet agents. The pattern of prescribing at discharge corresponded closely with the use of cardioactive agents at the time of survey and with drugs reported to have been taken continuously since discharge to the time of survey.

CONCLUSIONS

These data suggest that follow-up care after AMI is both comprehensive and widespread. Such care may have contributed significantly to the overall decline in mortality from ischaemic heart disease.

Measuring the incidence of acute myocardial infarction: the problem of possible acute myocardial infarction

Variations in the ratio of "definite" to "possible" myocardial infarction for non-fatal cases were examined in studies that used World Health Organization criteria. There were large variations in this ratio, variations which appeared to be due to differences in the ascertainment of non-fatal cases of "possible" myocardial infarction, which, in turn, contributed to reported differences in the incidence of myocardial infarction. A significant proportion of cases of "possible" myocardial infarction probably do not have ischemic heart disease at all, since, in our data, cases of "possible" myocardial infarction (non-fatal) with a hospital discharge diagnosis of chest pain (undiagnosed) had a risk of death that was no worse than that in the general population. Thus the most reproducible, and possibly most accurate estimates of the incidence of myocardial infarction may come from including only fatal cases of "possible" myocardial infarction with both fatal and non-fatal cases of "definite" myocardial infarction.

Surgeon experience and trends in intraoperative complications in laparoscopic cholecystectomy

BACKGROUND

Intraoperative complications, particularly bile duct injuries (BDIs), have increased since the introduction of laparoscopic cholecystectomy (LC). This excess risk is expected to decline as surgeon experience in laparoscopic surgery increases.

METHODS

This was a population-based study of trends in intraoperative injuries in 33 309 cholecystectomies carried out in Western Australia between 1988 and 1998, based on hospital discharge abstracts. Endpoints were identified from diagnostic and procedure codes in index or postoperative readmissions, or a register of endoscopic retrograde cholangiopancreatography procedures, and validated using hospital records. Multivariate analysis was used to estimate the risk of complications associated with potential risk factors.

RESULTS

Following the introduction of LC in 1991, the prevalence of all complications doubled by 1994 then stabilized, whereas that of BDI declined after 1994. The risk of complications increased with age, was higher in men, teaching and country hospitals, and was higher for LC and more complicated operations. It was lower when intraoperative cholangiography was performed and with increasing surgeon experience. Approximately 20 per cent of all complications and 30 per cent of BDIs were attributable to surgeons who had performed 200 or fewer cholecystectomies in the previous 5 years.

CONCLUSION

The risk of intraoperative complications declined with increasing surgical experience and use of intraoperative cholangiography.

Prior calcium channel blockade and short-term survival following acute myocardial infarction

There is concern over the safety of calcium channel blockers (CCBs) in acute coronary disease. We sought to determine if patients taking calcium channel blockers (CCBs) at the time of admission with acute myocardial infarction (AMI) had a higher case-fatality compared with those taking beta-blockers or neither medication. Clinical and drug treatment variables at the time of hospital admission predictive of survival at 28 days were examined in a community-based registry of patients aged under 65 years admitted to hospital for suspected AMI in Perth, Australia, between 1984 and 1993. Among 7766 patients, 1291 (16.6%) were taking a CCB and 1259 (16.2%) a betablocker alone at hospital admission. Patients taking CCBs had a worse clinical profile than those taking a beta-blocker alone or neither drug (control group), and a higher unadjusted 28-day mortality (17.6% versus 9.3% and 11.1% respectively, both P < 0.001). There was no significant heterogeneity with respect to mortality between nifedipine, diltiazem, or verapamil when used alone, or with a beta-blocker. After adjustment for factors predictive of death at 28 days, patients taking a CCB were found not to have an excess chance of death compared with the control group (odds ratio [OR] 1.06, 95% confidence interval [CI]; 0.87, 1.30), whereas those taking a beta-blocker alone had a lower odds of death (OR 0.75, 95% CI; 0.59, 0.94). These results indicate that established calcium channel blockade is not associated with an excess risk of death following AMI once other differences between patients are taken into account, but neither does it have the survival advantage seen with prior beta-blocker therapy.

Underuse of beta-blockers following myocardial infarction: a tale of two cities

AIMS

To measure factors associated with underuse of beta-blocker therapy after myocardial infarction (MI).

METHODS

The Newcastle and Perth collaborating centres of the World Health Organization (WHO) MONICA project (to MONItor trends and determinants of Cardiovascular disease) systematically evaluated all patients admitted to hospital in their respective regions with possible MI. A total of 1766 patients in Newcastle and 4,503 patients in Perth, discharged from hospital after confirmed MI from 1985 to 1993, were studied. Rates of beta-blocker use before and after hospital discharge were evaluated and correlates of beta-blocker use determined.

RESULTS

Beta-blocker use was similar in Newcastle and Perth before MI (21% of patients in each centre). During hospital admission, beta-blocker therapy was initiated nearly twice as frequently in Perth compared with Newcastle (66 vs 36%, respectively) and more patients were discharged from hospital on beta-blockers in Perth (68%) than in Newcastle (45%). The main factors associated with underuse of beta-blockers in multivariate analysis were geographical centre (odds ratio (OR) for Newcastle compared with Perth 0.3; 95% confidence interval (CI) 0.3-0.3), a history of previous MI (OR 0.6, 95% CI 0.5-0.7), admission to hospital in earlier years (OR 0.4, 95% CI 0.3-0.4 for years 1985-87 compared with years 1991-93), diabetes (OR 0.6, 95% CI 0.5-0.8) and the concomitant use of diuretics (OR 0.5, 95% CI 0.4-0.6) and calcium antagonists (OR 0.6, 95% CI 0.5-0.8).

CONCLUSIONS

Underuse of beta-blockers after MI was strongly related to hospital prescribing patterns and not to community use of beta-blockers. Underuse occurred in patients with diabetes and in patients with left ventricular dysfunction, patients who stand to benefit most from beta-blocker use following MI.

Opportunities for control of coronary heart disease in Australia

OBJECTIVE

To estimate the number of coronary events that could be prevented in Australia each year by the use of preventive and therapeutic strategies targeted to subgroups of the population based on their levels of risk and need.

METHODS

Estimates of risk reduction from the published literature, prevalence estimates of elevated risk factor levels from the 1995 National Health Survey and treatment levels from the Australian collaborating centres in the World Health Organization's MONICA Project were used to calculate numbers of coronary events preventable among men and women aged 35-79 years in Australia.

RESULTS

Approximately 14,000 coronary events could be avoided each year if the mean level of cholesterol in the population was reduced by 0.5 mmol/L, smoking prevalence was halved and prevalence of physical inactivity was reduced to 25%. This represents a reduction in coronary events of about 40%. Even with less optimistic targets, a reduction of 20% could be attained, while the achievement of some internationally recommended targets could lead to almost 50% reduction. In the short term, aggressive medical treatment of people with elevated levels of risk factors and established coronary disease offers the greatest opportunity for reducing coronary events.

CONCLUSION

A comprehensive approach to reduce levels of behavioural and biological risk factors and improve the use of effective treatment could lead to a large reduction in coronary event rates. In the long term, primary prevention--especially to reduce smoking, lower cholesterol levels and increase exercise--has the potential to reduce the population levels of risk and hence contain the national cost of coronary disease.

Cocaine inhibits human neutrophil phagocytosis and phagolysosomal acidification in vitro

Cocaine, used intravenously, increases the risk of infections, but its effects on neutrophil phagocytosis have not been examined in vitro. Human neutrophils were suspended in cocaine hydrochloride 0, 1, 10, 50, 100 or 200 microg/ml in Hank's balanced salt solution to which was added a phagocytic meal of killed Saccharomyces cerevisiae stained with the pH indicator dye bromcresol purple. Yeast per phagocytosing neutrophil and the percent neutrophils phagocytosing yeast were reduced in neutrophils treated with cocaine 100 and 200 microg/ml (P < 0.05). When examined for percent of yeast phagocytosed after 10 minutes, neutrophils treated with cocaine 1-200 microg/ml demonstrated a decrease (P < 0.05). However, at 60 minutes only neutrophils treated with cocaine 50 and 100 microg/ml still showed a decrease in percent of yeast phagocytosed. Phagolysosomal acidification was impaired in neutrophils treated with 50, 100 and 200 microg/ml cocaine. Thus, cocaine inhibits neutrophil phagocytosis and phagolysosomal acidification in vitro, offering a reason for cocaine users/abusers to have impaired host defense and to be potentially at higher risk for infections.

Population-based linkage of health records in Western Australia: development of a health services research linked database

OBJECTIVES

To introduce the Western Australian Health Services Research Linked Database as infrastructure to support aetiologic, utilisation and outcomes research. To compare the study population, data resources, technical systems and organisational supports with international best practice in record linkage and health research.

METHOD AND RESULTS

The WA Linked Database systematically links the available administrative health data within an Australian State of 1.7 million people. It brings together, initially, six core data elements (birth records, midwives' notifications, cancer registrations, in-patient hospital morbidity, in-patient and public out-patient mental health services data and death records). It will be updated regularly and is designed, in future extensions, to include data on primary, residential and domiciliary care and health surveys. Linkage uses probabilistic matching of patient names and other identifiers. Geocodes for spatial analysis are assigned using address linkage and mapping software. By June 1997, the project had taken 2 1/2 years to develop the system and link seven million core data records from 1980 to 1995.

CONCLUSIONS

The system is consistent with international benchmarks, from four centres of excellence, for the study population, core datasets, matching and geocoding, and collaborative networks. There are prospects to redress deficiencies in primary medical contact and other data resources, validation studies, tracing systems and a more supportive legal framework.

IMPLICATIONS

The WA Linked Database will be used in combination with medical record audits to provide a comprehensive evaluation of health system performance.

Finding bile duct injuries using record linkage: a validated study of complications following cholecystectomy

Laparoscopic cholecystectomy was introduced to Western Australia in 1991 and has become the method of choice for this procedure, although there are concerns about complications, particularly bile duct injuries. Previous studies have investigated this problem but have not confirmed the accuracy of coded information. We used Record Linkage to link operative admissions to subsequent admissions for all people who underwent cholecystectomy between 1988 and 1994. Using ICD9-CM discharge codes, we identified patients with an associated complication. We validated these patients' medical notes to obtain the proportion of complications in the period encompassing the introduction of laparoscopic cholecystectomy. We found 48 bile duct injuries in 413 patients. Of these 43% were found using complication codes on the operative admission, 79% using linked records of subsequent admissions, and 90% by adding lists of complicated cases from the three teaching hospitals. Any epidemiological research that uses surgical complication codes from operative admissions, particularly in the absence of a specific ICD9-CM code, will lead to significantly underestimating the prevalence of complications. By using record linkage, and validating medical records, we captured a significant proportion of complications.

Complications of cholecystectomy: risks of the laparoscopic approach and protective effects of operative cholangiography: a population-based study

BACKGROUND

Previous studies suggest that laparoscopic cholecystectomy (LC) is associated with an increased risk of intraoperative injury involving the bile ducts, bowel, and vascular structures compared with open cholecystectomy (OC). Population-based studies are required to estimate the magnitude of the increased risk, to determine whether this is changing over time, and to identify ways by which this might be reduced.

METHODS

Suspected cases of intraoperative injury associated with cholecystectomy in Western Australia in the period 1988 to 1994 were identified from routinely collected hospital statistical records and lists of persons undergoing postoperative endoscopic retrograde cholangiopancreatography. The case records of suspect cases were reviewed to confirm the nature and site of injury. Ordinal logistic regression was used to estimate the risk of injury associated with LC compared with OC after adjusting for confounding factors.

RESULTS

After the introduction of LC in 1991, the proportion of all cholecystectomy cases with intraoperative injury increased from 0.67% in 1988-90 to 1.33% in 1993-94. Similar relative increases were observed in bile duct injuries, major bile leaks, and other injuries to bowel or vascular structures. Increases in intraoperative injury were observed in both LC and OC. After adjustment for age, gender, hospital type, severity of disease, intraoperative cholangiography, and calendar period, the odds ratio for intraoperative injury in LC compared with OC was 1.79. Operative cholangiography significantly reduced the risk of injury.

CONCLUSION

Operative cholangiography has a protective effect for complications of cholecystectomy. Compared with OC, LC carries a nearly twofold higher risk of major bile, vascular, and bowel complications. Further study is required to determine the extent to which potentially preventable factors contribute to this risk.

Arrhythmias and mortality after myocardial infarction in diabetic patients. Relationship to diabetes treatment

OBJECTIVE

To assess the relationship between clinical course after acute myocardial infarction (AMI) and diabetes treatment.

RESEARCH DESIGN AND METHODS

Retrospective analysis of data from all patients aged 25-64 years admitted to hospitals in Perth, Australia, between 1985 and 1993 with AMI diagnosed according to the International Classification of Diseases (9th revision) criteria was conducted. Short- (28-day) and long-term survival and complications in diabetic and nondiabetic patients were compared. For diabetic patients, 28-day survival, dysrhythmias, heart block, and pulmonary edema were treated as outcomes, and factors related to each were assessed using multiple logistic regression. Diabetes treatment was added to the model to assess its significance. Long-term survival was compared by means of a Cox proportional hazards model.

RESULTS

Of 5,715 patients, 745 (12.9%) were diabetic. Mortality at 28 days was 12.0 and 28.1% for nondiabetic and diabetic patients, respectively (P < 0.001); there were no significant drug effects in the diabetic group. Ventricular fibrillation in diabetic patients taking glibenclamide (11.8%) was similar to that of nondiabetic patients (11.0%) but was lower than that for those patients taking either gliclazide (18.0%; 0.1 > P > 0.05) or insulin (22.8%; P < 0.05). There were no other treatment-related differences in acute complications. Long-term survival in diabetic patients was reduced in those taking digitalis and/or diuretics but type of diabetes treatment at discharge had no significant association with outcome.

CONCLUSIONS

These results do not suggest that ischemic heart disease should influence the choice of diabetes treatment regimen in general or of sulfonylurea drug in particular.

Vitamin A and cancer prevention I: observations in workers previously exposed to asbestos at Wittenoom, Western Australia

Our aim was to describe a vitamin A-based cancer prevention program for former asbestos workers and to check for possible harmful effects by comparing rates of disease and death in study subjects with subjects who chose not to join. All subjects had been occupationally exposed to crocidolite at Wittenoom Gorge between 1943 and 1966; 1,677 subjects indicated interest in the program and 1,203 joined between June 1990 and May 1995. Comparison subjects consisted of 996 former workers known to be alive in Western Australia in 1990 who did not join the program. Program subjects were provided with annual supplies of vitamin A (either synthetic beta-carotene or retinol), help in quitting smoking and dietary advice. The comparison group received only mail contact. Both groups were followed up to December 1994 for vital status and cancer information, and rates of cancer and death from various causes were compared. Mortality in both groups was higher than expected (standardised mortality ratio 1.23 in program subjects and 1.67 in comparison subjects). After adjustment for age, smoking and asbestos exposure, the relative rates in participants compared with non-participants was below I for all examined cancers and causes of death. For mesothelioma and lung cancer, group differences increased with time from entry, whereas other differences dissipated with time. No significant side effects were reported. In conclusion, program participants had significantly lower mortality than non-participants, but the rates of the 2 groups converged with time.

Vitamin A and cancer prevention II: comparison of the effects of retinol and beta-carotene

Former blue asbestos workers known to be at high risk of asbestos-related diseases, particularly malignant mesothelioma and lung cancer, were enrolled in a chemo-prevention program using vitamin A. Our aims were to compare rates of disease and death in subjects randomly assigned to beta-carotene or retinol. Subjects were assigned randomly to take 30 mg/day beta-carotene (512 subjects) or 25,000 IU/day retinol (512 subjects) and followed up through death and cancer registries from the start of the study in June 1990 till May 1995. Comparison between groups was by Cox regression in both intention-to-treat analyses and efficacy analyses based on treatment actually taken. Median follow-up time was 232 weeks. Four cases of lung cancer and 3 cases of mesothelioma were observed in subjects randomised to retinol and 6 cases of lung cancer and 12 cases of mesothelioma in subjects randomised to beta-carotene. The relative rate of mesothelioma (the most common single cause of death in our study) for those on retinol compared with those on beta-carotene was 0.24 (95% CI 0.07-0.86). In the retinol group, there was also a significantly lower rate for death from all causes but a higher rate of ischaemic heart disease mortality. Similar results were found with efficacy analyses. Our results confirm other findings of a lack of any benefit from administration of large doses of synthetic beta-carotene. The finding of significantly lower rates of mesothelioma among subjects assigned to retinol requires further investigation.

Environmental exposure to crocidolite and mesothelioma: exposure-response relationships

This study aimed to estimate exposure-response relationships for mesothelioma and environmental exposure to crocidolite. All 4,659 former residents of Wittenoom, Western Australia (WA) who lived there between 1943 and 1993 for at least 1 mo and were not directly employed in the crocidolite industry, were followed-up through the WA death, cancer and mesothelioma registries, electoral rolls, and telephone books. In 1992, all subjects who should be traced were sent a questionnaire. Exposure levels were estimated from results of periodic environmental surveys and duration of residence. Incidence rates were standardized to the World Population and Cox Regression was used to estimate the effects of exposure on incidence. To the end of 1993, 27 cases of mesothelioma were diagnosed. Mesothelioma cases stayed longer at Wittenoom, had a higher average intensity of exposure, and a higher cumulative exposure to crocidolite than control subjects. The standardized incidence of mesothelioma was 260 per million person-years, and was similar for males and females. The rate increased significantly with time from first exposure, duration of exposure and cumulative exposure. At these levels of crocidolite exposure, there is a significantly increased risk of mesothelioma, which is dose-dependent.

Declining rates of coronary heart disease in New Zealand and Australia, 1983-1993

The authors report the results of 10 years of monitoring of trends in the rates of major nonfatal and fatal coronary events and in case fatality in Auckland, New Zealand, and in Newcastle and Perth, Australia. Continuous surveillance of all suspected myocardial infarctions and coronary deaths in people aged 35-64 years was undertaken in the three centers as part of the World Health Organization's Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) Project. For nonfatal definite myocardial infarction, there were statistically significant declines in rates in all centers in both men and women, with estimated average changes between 2.5% and 3.7% per year during the period 1984-1993. Rates of all coronary deaths also declined significantly in all three populations for both men and women. In absolute terms, there was, in general, a greater reduction in prehospital deaths than in deaths after hospitalization. Although 28-day case fatality remains high at between 35% and 50%, in the Australian centers it declined significantly by between 1.0% and 2.9% per year, and in Auckland there was also a small decline. However, since most deaths occur outside the hospital in people without a previous history of coronary heart disease, an increased emphasis on primary prevention is necessary.

Exposure to crocidolite and the incidence of different histological types of lung cancer

OBJECTIVES

To estimate the relations between exposure to both tobacco smoke and crocidolite and the incidence of various histological types of lung cancer.

METHODS

In 1979 all former workers from the Wittenoom asbestos industry who could be traced were sent a questionnaire on smoking history. Of 2928 questionnaires sent, satisfactory replies were received from 2400 men and 149 women. Of the men, 80% had smoked at some time and 50% still smoked. Occupational exposure to crocidolite was known from employment records and follow up was maintained through death and cancer registries in Australia with histological diagnoses obtained from the relevant State Cancer Registry. Conditional logistic regression was used to estimate the effects of tobacco and asbestos exposure on incidence of different cell types of lung cancer in a nested case-control design.

RESULTS

Between 1979 and 1990, 71 cases of lung cancer occurred among men in this cohort: 27% squamous cell carcinoma, 31% adenocarcinoma, 18% small cell carcinoma, 11% large cell carcinoma, and 13% unclassified or indeterminate. Two of the classified cases and one unclassified case had never smoked. The incidence of both squamous and adenocarcinoma types of lung cancer were greatest in ex-smokers and in those subjects with the highest levels of exposure to crocidolite. After adjustment for smoking habit, the increase in incidence of lung cancer with increasing exposure to crocidolite was greater for squamous cell carcinoma than for adenocarcinoma.

CONCLUSIONS

The results from this study have shown significant exposure-response effects for exposure to crocidolite, and both adenocarcinoma and squamous cell carcinoma of the lung. They also provide some further evidence against the theory that parenchymal fibrosis induced by asbestos is a necessary precursor to asbestos induced lung cancer.

Mortality trends, 1965 to 1989, in Busselton, the site of repeated health surveys and interventions

The community of Busselton in Western Australia has participated in repeated cross-sectional health surveys and other health interventions since 1966. Health surveys of adults were conducted every three years from 1966 to 1981. Health interventions, including programs for high blood pressure, smoking, high blood cholesterol levels and obesity, were implemented in the community. Mortality rates for the Busselton area are compared with rates for the remainder of the southwest region of Western Australia in an attempt to determine if the surveys and associated interventions have had any impact on survival. Statistical comparisons via Poisson regression analysis showed that mortality rates for males over the period 1965 to 1989 in Busselton declined at a similar rate to the southwest. However, for females, especially those aged 45 to 74 years, mortality rates declined significantly faster in Busselton than in the southwest, suggesting a beneficial impact on survival of the surveys and associated interventions.

Early identification of patients at low risk of death after myocardial infarction and potentially suitable for early hospital discharge

OBJECTIVES

To find (a) whether data available shortly after admission for acute myocardial infarction can provide a reliable prognostic indicator of survival at 28 days, and (b) whether such an indicator might be used to identify patients at low risk of death and suitable for early discharge.

DESIGN

Retrospective analysis of data collected on patients admitted to a coronary care unit for acute myocardial infarction. A validation sample was selected at random from these patients.

SETTING

Coronary care units in Perth, Western Australia.

SUBJECTS

6746 patients aged under 65 and resident in the Perth Statistical Division who during 1984-92 were admitted to a coronary care unit with symptoms of myocardial infarction.

MAIN OUTCOME MEASURES

Sensitivity and specificity of several models for predicting survival at 28 days after myocardial infarction, and detailed performance characteristics of a particular model.

RESULTS

Patients with a pulse rate of 100 beats/min or less, aged 60 or under, and with symptoms typical of myocardial infarction, no past history of myocardial infarction or diabetes, and no significant Q wave in the admission electrocardiogram had a very high chance of survival at 28 days (99.2%). These patients made up one third of all patients studied.

CONCLUSION

The prognostic index identifies patients very soon after admission who are at low risk of death and potentially eligible for early discharge from hospital or the coronary care unit. Computing the index does not need complex cardiac investigations.

Coronary heart disease case fatality in four countries. A community study. The Acute Myocardial Infarction Register Teams of Auckland, Augsburg, Bremen, FINMONICA, Newcastle, and Perth

BACKGROUND

Community-based registers participating in the MONICA Project of the World Health Organization show markedly different attack and death rates of coronary heart disease. This variation is a function of both the incidence and case fatality occurring within countries. The contribution of case fatality to the international variation in coronary heart disease mortality rates is not well understood.

METHODS AND RESULTS

The register data from eight study populations--Augsburg and Bremen in Germany, Auckland in New Zealand, Perth and Newcastle in Australia, and North Karelia, Kuopio, and Turku/Loimaa in Finland--were compared. All patients with definite myocardial infarction or coronary death aged 35 to 64 years occurring in the study populations in 1985 through 1989 are the basis for the case fatality calculations by different definitions: 28-day case fatality for all cases, for hospitalized cases, and for hospitalized 24-hour survivors; out-of-hospital case fatality; and 24-hour case fatality for hospitalized cases. Differences in case fatality were much smaller than differences in attack and mortality rates in these populations. About two thirds of deaths occurred before the patients reached a hospital. The 28-day case fatality ranged from 37% for men in Perth to 58% for women in Augsburg. Among those who reached the hospital alive, 28-day case fatality was 13% to 27% for men and 20% to 35% for women. In those who survived 24 hours from the onset of symptoms, 28-day case fatality was 8% to 17% for men and 12% to 26% for women.

CONCLUSIONS

Differences in case fatality were not associated with differences in coronary mortality rates between these populations. As most deaths occurred before reaching a hospital, opportunities for reducing case fatality through improved hospital care are limited. This emphasizes the primary role of prevention in reducing coronary death rates.

Radiographic abnormalities and mortality in subjects with exposure to crocidolite

Plain chest radiographs from a one in six random sample of the workforce of the asbestos industry at Wittenoom, Western Australia between 1943 and 1966 have been classified for degree of profusion and pleural thickening by two independent observers according to the 1980 UICC-ILO Classification of Radiographs for the pneumoconioses to clarify the effect of degree of radiological abnormality on survival. A total of 1106 subjects were selected. Each subject's age, cumulative exposure to crocidolite, and time since first exposure were determined from employment records, the results of a survey of airborne concentrations of fibres > 5 mu in length conducted in 1966, and an exposure rating by an industrial hygienist and an ex-manager of the mine and mill at Wittenoom. By the end of 1986 193 subjects had died. Conditional logistic regression was used to model the relative risk of death in five separate case-control analyses in which the outcomes were deaths from: (1) all causes, (2) malignant mesothelioma, (3) lung cancer, (4) asbestosis, and (5) other causes excluding cancer and asbestosis. Up to 20 controls per case were randomly chosen from all men of the same age who were not known to have died before the date of death of the index case. After adjustment for exposure and time since first exposure, there were significant and independent effects of radiographic profusion and pleural thickening on all cause mortality. The effect of profusion was largely a result of the effect on mortality from malignant mesothelioma and asbestosis but not lung cancer. The effect of pleural thickening was greatest on mortality from other causes, mainly ischaemic heart disease. This study has shown that degree of radiographic abnormality has an independent effect on mortality from malignant mesothelioma, asbestosis, and all causes even after allowing for the effects of age, degree of exposure, and time since first exposure.

A study of the characteristics and needs of people transferred from acute hospitals to nursing homes

OBJECTIVES

To describe the categories of people being approved for admission to nursing homes; to consider whether any alternatives would have been more appropriate; and to outline the care needed for each category.

PARTICIPANTS AND SETTING

Patients in acute-care facilities in metropolitan Perth for whom a request had been made for nursing home admission.

DESIGN

Patients were interviewed (by R B L and M D) and records in the acute hospital were examined. A second interview of those patients still available was conducted after their transfer to the nursing home.

RESULTS

Nursing care was considered necessary for 123 of the 201 people seen in the acute hospitals; domestic care in a standard hostel for 24 people; care in a special dementia unit (SDU) hostel for 26 people; and care in a psychiatric institution for 16 people. Twelve others had various specific needs. Several different categories were identified in the group needing nursing care.

CONCLUSIONS

Applicants for nursing home admission do not form a homogeneous group; there are several categories with different needs. SDU hostels should be added to the available facilities. In addition to undertaking the assessment of nursing home applicants, personnel from geriatric services should be encouraged to become involved in their continuing care.

Retention and survival of hostel residents--a 12 year study

BACKGROUND

The admission of a proportion of disabled people to hostels is inevitably followed by their transfer to nursing homes. Our hypothesis was that such admissions are justified in terms of quality of life and the cost to the community, notwithstanding the necessity of subsequent transfer.

AIMS

To test this hypothesis by measuring the retention and survival times of residents in hostel and in nursing home; to consider the relevance of these factors to the future policy of the two institutions.

METHODS

A retrospective study was made of 159 residents admitted over a period of 12 years to a hostel with 32 places. Times spent in the hostel and in the nursing home were recorded. Probabilities of survival in hostel and in nursing home were calculated according to the Kaplan-Meier method. Comparison with the expected survival of a matched cohort of the total population was determined. Estimation was made, using the SAS software package, of the likely number of places needed in nursing homes for residents following transfer.

RESULTS

Although the majority of hostel residents eventually needed nursing home care, a worthwhile proportion of their total institutional time (approximately two-thirds) was spent in the hostel. Ongoing support from the personnel in a geriatric service is likely to increase retention time in the hostel. Because of the ultimate outcome for the majority of residents, planning for hostel care should include consideration of places needed in nursing homes.

Malignant mesothelioma after environmental exposure to blue asbestos

To determine the magnitude of the population at risk from non-occupational exposure to crocidolite at Wittenoom, Western Australia (WA), a cohort of 4,890 residents who never worked for the mining company Australian Blue Asbestos (ABA) has been assembled from all 18,553 available records: the local school register, hospital attendances, the WA electoral roll, birth certificates, workers who answered a mailed questionnaire in 1979, participants in a cancer-prevention programme using vitamin-A dietary supplements, and other sources. The majority of subjects were relatives and friends of ABA employees, and nearly half the cohort were either born at Wittenoom or first went there as children under 10 years of age. As most residents were at Wittenoom when the mine and mill were in operation during the period 1943 to 1966, 82% were first exposed to crocidolite 20 or more years ago. The proportion of other workers (i.e., not employed by ABA) and their families increased once the mining operations ceased. To date, 24 cases of mesothelioma have been reported in this cohort: 9 males and 15 females. Time from first exposure to diagnosis ranged from 23 to 44 years and residence in Wittenoom ranged from 6 weeks to 11 years.

A five-year study of residents of a special hostel for people with dementia

In order to consider whether admission to a special hostel was a desirable policy in view of the likelihood of subsequent transfer to a nursing home, this study compared the time spent by residents in a special hostel with the period in a nursing home after they were transferred out of the hostel. We also estimated the number of nursing home places necessary for residents who were transferred and studied the reasons for transfer. The setting was a special hostel in Perth, Western Australia, for 36 people with moderate or severe dementia. The periods spent in the hostel or a nursing home were calculated for all residents admitted between 1985 and 1990. Forty-two of the 84 residents admitted during the study period were transferred to nursing homes. About two thirds of the total time in the two institutions was spent in the hostel. The two principal reasons necessitating transfer to a nursing home were advancing dementia and the addition of a physical impairment. Because a major proportion of the care of selected people with dementia (who can no longer remain at home) can be undertaken in a special hostel, this facility should be included with standard hostel and nursing home in arrangements for institutional care. Between 20 and 25 nursing home places are necessary for residents transferred from a hostel of this size.

The benefits of beta-blockade at the time of myocardial infarction

Data from the World Health Organization Monitoring Trends and Determinants in Cardiovascular Disease (WHO MONICA) project, collected in Perth, are described. Patients taking a beta-blocker at the time of onset of myocardial infarction are a high-risk group, but univariate analysis of the data showed that the overall survival of patients on beta-blockers at 28 days was the same as for those not taking beta-blockers. A multiple logistic regression model analysis showed that the patients treated with beta-blockers had a survival advantage at 28 days, with a relative risk of death of 0.5. The mechanism of benefit is unclear. It does not appear to be an anti-arrhythmic effect, because beta-blockers did not affect survival in the first 24 h following a myocardial infarction, nor did they affect ventricular fibrillation. The effect may be due to a reduction in myocardial necrosis. Furthermore, an analysis of the incidence of coronary disease and type of drugs prescribed in Perth has indicated that beta-blockers may be contributing to a decrease in mortality due to coronary events.

Mortality from coronary heart disease and incidence of acute myocardial infarction in Auckland, Newcastle and Perth

OBJECTIVE

To confirm the existence of regional differences in coronary death rates in Australia and New Zealand and to determine whether or not these are associated with parallel differences in the incidence of acute myocardial infarction.

DESIGN

Descriptive epidemiological study.

SETTING

Community based study.

SUBJECTS

Residents of Auckland, Newcastle and Perth aged 25-64 years admitted to hospital for acute myocardial infarction or dying from coronary heart disease between 1983 and 1987.

MAIN OUTCOME MEASURES

Definite acute myocardial infarction or coronary death classified according to the criteria of the World Health Organization MONICA project.

RESULTS

This study confirms the marked variation, evident from official statistics, in mortality rates from ischaemic heart disease between Newcastle (high), Auckland and Perth (low). A different pattern is observed for the incidence of acute myocardial infarction and there are also obvious differences between centres in the case fatality ratios for all acute coronary events combined. Newcastle has the highest rate for all coronary events, particularly in women. Auckland is characterised by substantially higher case fatality ratios compared with the two Australian cities. This is due especially to higher rates of coronary death outside hospital. Perth, which has the lowest mortality rates and case fatality ratios in both men and women, has rates for admission to hospital for acute myocardial infarction and all cases of ischaemic heart disease that are disproportionately high in relation to the corresponding mortality rates.

CONCLUSION

The differences in case fatality ratios between these three centres are not readily explained by artefacts related to enumeration or classification. Rather, they are most likely related to differences in the natural history of ischaemic heart disease in the three populations. Differences in medical management may also contribute to the substantial variation in mortality rates.

Risk factors for death in patients admitted to hospital with asthma: a follow-up study

Hospital records of patients with asthma admitted to teaching hospitals in Perth, Western Australia between 1976 and 1980 were examined retrospectively to identify characteristics of the illness which were associated with subsequent death. From 5722 admissions there were 195 deaths to December 1982, 186 of whom had records available (cases); 452 of the surviving subjects were used for comparison (controls). There was no difference in age of onset of asthma or cigarette smoking habits between the two groups, but ischaemic heart disease as an associated condition was significantly more frequent in cases. On admission to hospital an arterial PCO2 less than 45 mmHg was more frequent in those who died, but there were no differences in arterial PO2, lowest pH, highest or lowest FEV1 and FVC. Cases more frequently used home nebulisers and were more frequently prescribed corticosteroids, antibiotics and sedatives or tranquilizers prior to admission, corticosteroids and sedatives or tranquilisers during admission and sedatives or tranquilisers on discharge. These results suggest that cases had more severe asthma in that they were more often treated with home nebulisers, corticosteroids and antibiotics, but with the exception of PaCO2 the commonly used measurements of severity of asthma did not identify those at risk of death. The prescription of sedatives or tranquillisers appears to be associated with an increased risk of death in subjects with asthma.

Smoking, exposure to crocidolite, and the incidence of lung cancer and asbestosis

In 1979 all former workers from the Wittenoom asbestos industry who could be traced to an address were sent a questionnaire to determine smoking history. Occupational exposure to crocidolite was known from employment records. Of 2928 questionnaires sent, satisfactory replies were received from 2400 men and 149 women. Eighty per cent of these had smoked at some time and 50% were still smoking. Since that time 40 cases of lung cancer and 66 cases of compensatable asbestosis have occurred in this cohort. The incidence of both lung cancer and asbestosis was greatest in those subjects with the highest levels of exposure to crocidolite and in ex-smokers. Statistical modelling of the joint effects of these exposures on the incidence of each disease indicated that crocidolite exposure multiplied the rates of lung cancer due to smoking and that smoking has no measurable effect on the rates of asbestosis. There was also some evidence that the incidence rate of lung cancer is falling with time.

Reduced risk of death at 28 days in patients taking a beta blocker before admission to hospital with myocardial infarction

OBJECTIVE

To see whether patients taking an oral beta blocker at the time of admission to hospital with myocardial infarction have a reduced risk of death at 28 days.

DESIGN

Retrospective analysis of data collected on patients admitted over four years.

SETTING

Community based study.

PATIENTS

2430 Consecutive patients living in the Perth statistical division admitted to hospital with myocardial infarction during 1984-7.

MAIN OUTCOME MEASURE

Survival at 28 days among patients taking a beta blocker at onset of myocardial infarction.

RESULTS

Patients were grouped into those who were and were not taking a beta blocker at the time of admission. Though patients taking a beta blocker were older and more likely to have a history of myocardial infarction, angina, or hypertension, the overall mortality at 28 days was similar in the two groups. A logistic regression model used to adjust for factors predictive of cardiac death at 28 days confirmed that patients taking a beta blocker at the time of admission had a significantly reduced risk of death (relative risk 0.50; 95% confidence interval 0.34 to 0.76). Though the incidence of fatal ventricular fibrillation was similar in the two groups, mean peak creatine kinase activity was significantly lower in the beta blocker group.

CONCLUSIONS

These data support the value of long term use of beta blockers in patients at risk of myocardial infarction. They suggest that patients taking these agents before admission to hospital with myocardial infarction have a significant survival advantage at 28 days, which may be due to a reduction in infarct size.

Predictions of future cases of asbestos-related disease among former miners and millers of crocidolite in Western Australia

In a cohort of 6502 male and 410 female former workers from the crocidolite (blue asbestos) mining and milling works at Wittenoom, Western Australia, there were 94 cases of malignant mesothelioma (12 cases of peritoneal mesothelioma), 141 cases of lung cancer and 356 successful compensation claims for asbestosis to the end of 1986. After adjusting for measured covariate effects by means of proportional hazards regression analysis, smooth curves were fitted to the resulting "underlying" incidence rates for malignant mesothelioma, lung cancer and asbestosis, separately, and for mortality of any cause. By the use of these curves and individual risk estimates, predictions have been made of the future incidence of these diseases to the year 2020. With the assumption that all subjects who were not known to be dead or departed overseas still were alive at December 31, 1986, and excluding persons of more than 85 years of age, the number of new cases of mesothelioma is expected to rise to a peak of around 25 cases per year in 2010, with an expected total number of 692 cases of mesothelioma (95% confidence interval [CI], 394-990 cases) between 1987 and 2020. A total of 2898 deaths (95% CI, 2284-3511 deaths) of any cause is expected in the same period. New cases of lung cancer and asbestosis are expected to continue at roughly the current rates of eight and 17 cases per year, respectively, before declining after the year 2000, leading to totals of 183 cases (95% CI, 34-335 cases) and 482 cases (95% CI, 236-728 cases), respectively, being expected by the year 2020. Predictions that were based on the censoring of subjects at the date that they last were known to be alive resulted in slightly higher, but probably less accurate, estimates.

Cancer mortality in relation to measures of occupational exposure to crocidolite at Wittenoom Gorge in Western Australia

The separate and combined effects of duration and intensity of exposure to crocidolite on mortality from lung cancer, malignant mesothelioma, and stomach cancer were examined in 6506 male former crocidolite miners and millers at Wittenoom Gorge, Western Australia. Each subject who had died from lung cancer (92), mesothelioma (31), or stomach cancer (17) was matched with up to 20 control subjects of the same age who were not known to have died before the index subject. Relations of dose and time of exposure to crocidolite to risk of death were modelled by conditional logistic regression. For lung cancer, the best fitting multiplicative model was one which estimated a relative risk (RR) of 1.12 (95% CI 1.04-1.20) per year of exposure and 1.01 (95% CI 1.00-1.01) per fibre/ml. This was statistically indistinguishable from an additive model showing an increase in RR of 0.01045 (95% CI 0.008-0.020) per f/ml year. For mesothelioma the best fitting model appeared to be one estimating a RR of 24.9 (95% CI 3.51-1.77) per log year since first exposed and a RR of 10.5 (95% CI 3.12-35.1) if exposed for longer than six months. This was not distinguishable statistically from a model that showed mortality increasing as the fourth power of time since first exposed less the fourth power of time since last exposed. The effect of intensity of exposure on the RR for mesothelioma was only slight. There was no consistent effect of any measure of exposure to crocidolite on death from stomach cancer.

Trends in the incidence of myocardial infarction in Western Australia between 1971 and 1982

Trends in the incidence of and mortality from myocardial infarction in Perth, Western Australia, were studied for the period 1971 to 1982. The estimated age-adjusted incidence rate of myocardial infarction fell by 24% in males and 37% in females over this period. The rate fell in each of six age-sex groups, but the proportional decrease in those aged less than 45 years was nearly double that in those aged 45 years and over, as it was in females compared with males and in fatal cases compared with nonfatal cases. Over 80% of the decline in mortality was in deaths outside hospital. This and seven other comparable studies all showed a net decrease in the estimated incidence of myocardial infarction in both sexes, with median annual decreases of 2% in males and 3% in females. It is concluded that the decline in the incidence of myocardial infarction contributed substantially to the observed decrease in ischemic heart disease mortality, and that the most plausible explanation for the decline in incidence is a reduction in the prevalence of risk factors for myocardial infarction.

The incidence of malignant mesothelioma in Australia, 1947-1980

Details of patients with malignant mesothelioma that was diagnosed in Australia before 1981 were obtained by searching all possible sources throughout Australia as far into the past as possible and up to and including 1980. The earliest patient with mesothelioma who was identified was diagnosed in Victoria in 1947. By 1980, 535 (81%) men and 123 (19%) women had been diagnosed with the disease; only 14 persons were aged less than 35 years at the time of diagnosis (the youngest person was 15 years of age). The incidence rate in subjects who were 35 years or older at diagnosis was less than 1.0 cases per million person-years until 1964-1968, and then it rose progressively to 15.5 cases per million person-years in 1979-1980. The highest rate (69.7 cases per million person-years) was observed in 65- to 74-year-old men in 1979-1980. The incidence rate in Western Australia was greater than were the rates in other states of Australia after the mid 1960s. Pleural mesotheliomas accounted for 88% of cases in which the site of the tumour was known; peritoneal mesotheliomas accounted for 10% of such cases and "other" sites for 2% of such cases. In 6% of cases the site was not specified. The exposure to asbestos was stated as "definite" in 59% of the cases with a recorded history of exposure: 8% of all the cases in the study had been exposed to crocidolite (blue asbestos) from Wittenoom Gorge in Western Australia. The age at diagnosis of patients with known exposure to asbestos was similar to that in those without known exposure. The increases in the incidence of malignant mesothelioma in Australia follow the published trends in the production and use of the amphibole varieties of asbestos in this country after a lag period of between 20 and 30 years.

Mortality in miners and millers of crocidolite in Western Australia

It is known that 6505 men and 411 women were employed in the mining and milling of crocidolite at Wittenoom in the Pilbara region of Western Australia between 1943 and 1966. Employment was usually brief (median duration four months) and exposure intense (median estimated cumulative exposure 6 fibres/cc years). The vital status of 73% of the men and 58% of the women employed in the industry was known at 31 December 1980, providing 95 264 person-years of follow up with 820 deaths in men and 4914 person-years with 23 deaths in women. The standardised mortality ratio (SMR) for all causes in men was 1.53 (95% confidence interval 1.43 to 1.64). Statistically significant excess death rates were observed in men for neoplasms, particularly malignant mesothelioma (32 deaths), neoplasms of the trachea, bronchus, and lung (SMR 2.64), and neoplasms of the stomach (SMR 1.90); respiratory diseases, particularly pneumoconiosis (SMR 25.5); infections, particularly tuberculosis (SMR 4.09); mental disorders particularly alcoholism (SMR 4.87); digestive diseases, particularly peptic ulceration (SMR 2.46) and cirrhosis of the liver (SMR 3.94); and injuries and poisonings, particularly non-transport accidents (SMR 2.36). The excess mortality from pneumoconiosis, malignant mesothelioma, and respiratory cancers, but not stomach neoplasms, was dependent on time since first exposure and cumulative exposure. There was no increase in mortality from laryngeal cancer (SMR 1.09) or neoplasms other than those listed. The SMR for all causes in women was 1.47 (95% confidence interval 0.98-2.21) and for neoplasms 1.99; there was one death from malignant pleural mesothelioma.

Mortality from asthma in Western Australia

From a cohort of all 5760 male and 4979 female patients who were admitted to WA hospitals and were discharged with a diagnosis of asthma between 1976 and 1980, 265 deaths in men and 189 deaths in women were identified by the end of 1982. The standardized mortality ratio (SMR) for all causes of death for this cohort was 1.6 for men (P less than 0.001) and 1.7 for women (P less than 0.001). Both sexes showed a significant increase in deaths that were attributable to asthma (SMR, 57.9), chronic airflow obstruction (SMR, 9.3) and ischaemic heart disease (SMR, 1.3). The excess death rates for asthma were observed in all age groups, but those for chronic airflow obstruction and ischaemic heart disease were present in older age groups only. These findings indicate that asthma remains a potentially fatal disease in the Australian community. The excess mortality ratios for chronic airflow obstruction that were observed in patients who were admitted to hospital with asthma also suggest that asthma may result in irreversible airflow obstruction.

Estimation of myocardial infarction mortality from routinely collected data in Western Australia

The accuracy of routinely collected mortality data for ischemic heart disease (IHD) as indicators of death from acute myocardial infarction (AMI) was assessed in ages 25-64 years, according to the WHO criteria defined in 1983. Cases were identified from computer records (linked for individuals) of all death certificates and hospital discharges in Western Australia between 1971 and 1982. Where the official cause was IHD about 90% of deaths fulfilled the WHO criteria for definite or possible AMI. Up to 10% of fatal cases of definite or possible AMI were coded to other causes in the official death statistics, however it appeared that variations in this figure with changes in coding practices could cause appreciable bias in the estimation of secular trends in IHD mortality. This problem could largely be overcome by reviewing fatal events where the death certificate was coded to one of a limited number of other ICD rubrics.

Identification of non-fatal myocardial infarction through hospital discharge data in Western Australia

The validity of identifying incident cases of non-fatal acute myocardial infarction (AMI) between 1971 and 1982 in Western Australia from routine hospital records was assessed in ages 25-64 years, according to the WHO criteria defined in 1970 and 1983. This was done by reviewing original data sources and by using the Perth Coronary Register of 1971 as an external reference. Events with a coded discharge diagnosis of acute or subacute ischemic heart disease were found to be highly sensitive (97%) for cases of "definite" AMI (WHO 1983 criteria). The specificity of such events was lower (positive predictive value of about 70%) and validation of these events would be necessary for studies requiring high specificity. The sensitivity and specificity of these events for "definite" AMI seemed quite stable over time with similar values being observed in 1971 and 1978. Although the situation for "possible" AMI (non-fatal) is less clear, certainly many more records would need to be reviewed to validate this diagnosis.

Prevalence of radiographic asbestosis in crocidolite miners and millers at Wittenoom, Western Australia

An estimate has been made of the prevalence of unrecognised pneumoconiosis in former crocidolite workers from Wittenoom, Western Australia. All plain chest radiographs relating to a one in six random sample (1025 men) of all former Wittenoom workers who had never entered a compensation claim to the Pneumoconiosis Medical Board of Western Australia were sought from Perth teaching hospitals and from the Perth Chest Clinic where compulsory examination of all workers in the mining industry takes place. Radiographs were recovered for 83% of the men and read independently by two observers. By means of logistic regression analysis a current prevalence of parenchymal abnormality (defined as a radiographic profusion of small opacities of category 1/0 or greater on the ILO classification) of nearly 20% was calculated after adjustment for age, time since first exposure, and cumulative exposure level. One hundred men randomly selected from those known to be alive in the sample were invited to attend for a new radiographic examination. Seventy four men attended and the predicted prevalence was confirmed. It is estimated from these data that there were between 450 and 900 former Wittenoom workers in Australia at the end of 1980 who had radiographic abnormality consistent with pneumoconiosis but had not claimed compensation or had asbestosis diagnosed. The data are consistent with there being no threshold dose of crocidolite exposure for the development of radiographic abnormality in this group.

Morphology of bronchogenic carcinoma in workers formerly exposed to crocidolite at Wittenoom Gorge in Western Australia

Cytology and histology material from 46 bronchogenic carcinomas occurring in ex-workers from the Wittenoom crocidolite mine and mill in Western Australia and a matched random sample of 234 other bronchogenic carcinomas occurring in Western Australia over the same period were reviewed by a single histopathologist without knowledge of asbestos exposure status. Squamous-cell carcinomas formed 45.7% of the cancers in the asbestos-exposed group but only 32.5% of the cancers in the comparison group. This difference could not be explained by differences in smoking history between the two groups of lung cancer patients or in the type of histopathological material available for review. The excess of squamous-cell cancers was observed in subjects both with and without parenchymal asbestosis.

Compensation, radiographic changes, and survival in applicants for asbestosis compensation

The survival of 354 claimants for compensation for pulmonary asbestosis among former workers of the Wittenoom crocidolite mine and mill in Western Australia has been examined. There were 118 deaths up to December 1982. The median time between start of work and claim for compensation was 17 years. The standardised mortality ratio (SMR) for deaths from all causes was 2.65 (p less than 0.0001). The SMR for pneumoconiosis was 177.2 (p less than 0.0001), bronchitis and emphysema 2.6 (p = 0.04), tuberculosis 44.6 (p less than 0.0001), respiratory cancer (including five deaths from malignant pleural mesothelioma) 6.4 (p less than 0.0001), gastrointestinal cancer 1.6 (p = 0.22), all other cancers 1.6 (p = 0.17), heart disease 1.4 (p = 0.07), and all other causes 2.18 (p = 0.004). Plain chest radiographs taken within two years of claiming compensation were found for 238 subjects and were categorised independently by two observers according to the International Labour Organisation criteria without knowledge of exposure or compensation details. Profusion of radiographic opacities, age at claiming compensation, work in the Wittenoom mill, and degree of disability awarded by the pneumoconiosis medical board were significant predictors of survival, but total estimated exposure to asbestos was not. Radiographic profusion and degree of disability were, however, predictable by total exposure. The median survival from claim for compensation was 17 years in subjects with ILO category 1 pneumoconiosis, 12 years in category 2, and three years in category 3.

Trends in ischemic heart disease mortality and morbidity in Perth Statistical Division

Trends in mortality from Ischemic Heart Disease (IHD) and other principal causes of death, and in hospital admission rates for Acute Myocardial Infarction (AMI) have been studied in residents aged 35-64 years of the Perth Statistical Division for the period 1968-1982. Death rates were based on data abstracted from official statistics or computer tapes of unit death records. Hospital admission rates were derived from the computer tapes of the Western Australian Hospital Inpatient Survey, 1968-1982. Since 1968, mortality from IHD has fallen in the Perth Statistical Division in both males and females by 30% and 33%, respectively. This fall has occurred principally in deaths occurring out-of-hospital and has been accompanied by similar falls in mortality from other vascular diseases and in total mortality. Hospital admission rates for Acute Myocardial Infarction (AMI) in the Perth Statistical Division have fallen since 1971 by 17% in males and 27% in females. These findings taken together suggest that the improvement in IHD mortality in Western Australia has been due mainly to a fall in the incidence of acute manifestations of IHD (sudden death and AMI), rather than improvements in case fatality. The possible underlying mechanisms responsible for this are discussed.

The fall in mortality from ischemic heart disease in Australia: has survival after myocardial infarction improved?

Trends in mortality and survival after myocardial infarction (MI) were studied by use of computerised death and hospital discharge records for 25 to 64 year old residents of the Perth Statistical Division between 1971 and 1979. Highly significant falls in ischemic heart disease (IHD) mortality rates were found for men (18%) and women (29%) but 4, 26 and 52 week survival after hospital admission for MI remained constant at around 88%, 84% and 81% respectively. Further, as 75% of all IHD deaths between 1971 and 1979 occurred before the victim was admitted to hospital, the survival of those receiving treatment would have had to be greatly improved to influence total mortality from IHD appreciably. As the age and sex composition of persons hospitalised for MI and the proportion of MI victims hospitalised did not change during the study period it would seem that improved survival after hospital admission for MI did not contribute to the fall in IHD deaths between 1971 and 1979.

Epidemiology of malignant mesothelioma in Western Australia

Crocidolite was mined and milled at Wittenoom Gorge in Western Australia from 1943 to 1966. Between 1960-1964 and 1980-1982, the estimated incidence of malignant mesothelioma in Western Australia rose from 0.6/100 000 in men and less than 0.1/100 000 in women, aged 35 years or older, to 6.6/100 000 in men and 0.7/100 000 in women in this age group. Overall, 97 (70%) of 138 patients with malignant mesothelioma had definite or probable exposure to asbestos; 76 of these (55%) to Western Australian crocidolite. Of the latter 76 patients, 56 had worked in the mine or mill at Wittenoom and 4 had non-occupational exposure in the Wittenoom area; the remaining 16 had been exposed to crocidolite elsewhere in the State. There were only 4 (3%) patients with malignant peritoneal mesothelioma, of whom three had been exposed to crocidolite.

Long-term prognosis after recovery from myocardial infarction: a nine year follow-up of the Perth Coronary Register

Patients registered by the 1971 Perth Coronary Register as having suffered a myocardial infarction were followed up for 9 years. The Register was a community-based study that used standard methods and criteria as part of a World Health Organization collaborative investigation. Of the 1078 patients studied, 77% survived the first 24 hr and 62% the first 28 days; 0.3% were lost to follow-up. For the 666 patients alive at 28 days, the crude 1, 5, and 9 year survival rates were 88%, 67%, and 52%, respectively. The relationship between 54 variables and the survival of patients alive 28 days after myocardial infarction was examined by life-table methods and the log rank test, and then by fitting a proportional hazards model to the data. The important prognostic factors were age, sex, past history of myocardial infarction, stroke, diabetes and hypertension, tachycardia at presentation, hypotension at presentation, and the occurrence of arrhythmias as short-term complications. The most appropriate mathematical description of the joint effects of the prognostic factors was a multiplicative model with no interaction.

Decline in rate of death from ischaemic heart disease in the United Kingdom

The rates of death from ischaemic heart disease in the United Kingdom in the years after 1968 were studied to establish whether any general trend had occurred. A decline in the rates began after 1973-4, was greatest in those aged 35-44 years, and occurred among both men and women and in each of the regions of England and in Wales and Scotland. Total dietary fat intake had started to fall about five years earlier, and this may provide part of the explanation. Changes in smoking habits also occurred but were more difficult to relate to the pattern of change in the death rates. If a general decline in ischaemic heart disease has begun in the United Kingdom a case may be made for close monitoring of changes in lifestyle and medical practice in different demographic groups to try to find the explanation.