Recent trends in mortality from and incidence of myocardial infarction in Stockholm

Time trends in the incidence of myocardial infarction among professional drivers in Stockholm 1977-96

AIMS

To investigate time trends in the incidence of first myocardial infarction (MI) among bus, taxi, and lorry drivers in Stockholm.

METHODS

In this population based case-control study, all first events of acute MI among men aged 40-69 in Stockholm County 1977-96 were identified using registers of hospital discharges and deaths. Controls were selected randomly from the general population. National censuses were used for information on occupational titles. A total of 20,364 cases and 136,342 controls were included in the study. Among these, 1183 cases and 6072 controls had worked as drivers.

RESULTS

During 1977-84 the MI incidence was higher in all three driver groups than among other manual workers. There was a decline in MI incidence among drivers as well as in the general population during the study period. The decline was greater among drivers than among other manual workers. During 1985-96 the relative risk remained increased compared to other manual workers among taxi and lorry drivers, but not among bus drivers.

CONCLUSIONS

Despite a reduced MI incidence for professional drivers in recent years, preventive measures to reduce the risk of MI in these occupational groups, and in particular among taxi and lorry drivers, continue to be of importance.

Recent time trends in acute myocardial infarction in Stockholm, Sweden

AIMS

The purpose of this study was to analyse time trends in first acute myocardial infarction (AMI) incidence in Stockholm County during 1984-1996.

METHODS AND RESULTS

The study base consisted of the population of Stockholm County 30-89 years old 1984-1996. New cases of first AMI in the study base were identified by combining information regarding hospital discharges and deaths. The diagnostic quality was evaluated for 2403 First-AMI cases 45-70 years old that occurred during 1992-1994. The evaluation indicated a very high agreement with diagnostic criteria of AMI among hospital treated cases. Among fatal cases outside hospital, the autopsy rate was nearly 70%. The incidence of first AMI declined during the study period for both men and women. In men, the age-adjusted incidence of first AMI was 18% lower in 1994-1996 than in 1984-1987 and in women it was 13% lower. The average yearly decline was 2% for men and 1.4% for women.

CONCLUSION

The results of this study suggest a continued decline in AMI incidence in Stockholm. A reduction in the proportion of regular smokers has probably contributed to this decline. Future trends in AMI incidence are difficult to predict in view of diverging trends in risk factors.

The effect of recurrent events on register-based estimates of level and trends in incidence of acute myocardial infarction

Although changes in incidence of first acute myocardial infarctions (AMI) are of primary interest in the evaluation of preventive efforts, only few studies have used this measure. In the present study, the risk of recurrence over time in subjects with first AMI is analyzed, and the effect of inclusion of recurrent cases on the estimation of level and trend in the incidence of AMI is evaluated. The National Patient Register of Hospital Discharges and the Causes-of-Death Register were linked, and all cases of admission for AMI and fatal manifestation of the disease since 1977 and until 1992 in the Danish population were identified. New events occurred during the following 12 years in 46% of men and 42% of women with their first AMI in 1980. Ninety percent of the recurrent events occurred during the first 5 years. Using absence of events during only 1 preceding year as the inclusion criteria, the incidence rate would be overestimated by about 20%-30%. However, if the preceding event-free period was of the same duration throughout the study period, the trends in AMI rates were not altered by expanding the event-free period up to 14 years before the index event. Although rates of AMI based on the total number of affected persons without AMI in the previous year overestimate the true incidence by 20%-30%, trends in these rates reflect trends in rates of first events with reasonable accuracy.

The validity of hospital discharge register data on coronary heart disease in Finland

We studied the validity of the Finnish hospital discharge register data on coronary heart disease (CHD) for the purposes of epidemiologic studies and health services research. The Finnish nationwide hospital discharge register (HDR) was linked with the FINMONICA acute myocardial infarction (AMI) register for the years 1983-1990. The frequency of errors in the HDR was assessed separately. Between 8% and 13% of hospitalized AMI events registered in the AMI Register were not found in the HDR with an ICD code for CHD. Problems with the register linkage and the use of some ICD code other than one of the codes for CHD explained these missing events. The frequency of errors in the personal identification number was about 5% in the early 1980s. After 1986 errors were found only occasionally. The diagnosis recorded in the HDR was the same as that in the discharge sheet in about 95% of hospitalizations. The positive predictive value of the ICD code 410 (AMI), compared with the FINMONICA definite+possible AMI category, was very high and stable, about 90% in all areas and all hospitals, but the sensitivity varied from 50% at local hospitals to 80% at central hospitals. In summary, data on CHD obtained from the Finnish hospital discharge register give, on average, a correct picture on changes in the occurrence of AMI in Finland and can, with necessary caution, be used in epidemiological studies and health services research. However, the classification of individual cases is not standardized in the HDR, but varies over time, between geographical areas and the levels of care. Therefore, these data should not be used without confirmation in studies where correct classification of individual outcomes is of crucial importance, such as follow-up studies and case-control studies.

Hospital discharge register data in the assessment of trends in acute myocardial infarction. FINMONICA AMI Register Study Team

We evaluated the reliability hospital discharge register data in the assessment of acute myocardial infarction trends. In the FINMONICA study areas, trends in age standarized attack rates for the years 1983-90 were calculated independently from two sources: the nationwide Finnish hospital discharge register and the FINMONICA acute myocardial infarction register. The trends were compared by a statistical regression model. The trends obtained from the hospital discharge register were very similar to the trends obtained from the FINMONICA acute myocardial infarction register. The attack rates differed significantly, however, and the change in the International Classification of Diseases version from version 8 to version 9 brought on a change in the attack rates obtained from the hospital discharge register. Thus, hospital discharge register data can be used to assess acute myocardial infarction trends in the community. However, modifications of the International Classification of Diseases codes (new versions of the classification) and changes in the clinical use of the codes for coronary heart disease can have an impact on the attack rates obtained from the hospital discharge register, and the reliability of the hospital discharge register data should be regularly assessed.

Validity of information on gynecological operations in the Swedish in-patient registry

In order to validate information held at the Swedish In-patient Registry on oophorectomy and/or hysterectomy procedures, the register codes were compared with data from the medical records in a random sample of 1,338 women. Only 1% of these codes were missing but 5% were erroneous, which in most cases meant that the oophorectomy had been misclassified. The positive predictive value of operation codes was high, ranging from 86 to 100% of the registered events. The actual procedures among women registered with a code for hysterectomy with or without oophorectomy comprised hysterectomy alone in 47% of the women and hysterectomy with a bilateral or unilateral oophorectomy in 30% and 20%, respectively. The reliability of register codes for major gynecological surgical procedures is good, but when the code for hysterectomy is used, medical record data are needed to ascertain the ovarian status. Revised codes are therefore recommended.

Are geographical differences and time trends in myocardial infarction incidence in Sweden real? Validity of hospital discharge diagnoses

In Sweden, acute myocardial infarction (AMI) incidence has been found to differ considerably between the neighboring counties of Stockholm and Gävleborg, with an increase in Stockholm during the 1970s. We estimated the AMI incidence in Stockholm in 1973 and in both areas in 1981. To determine if there were differences in the validity of hospital discharge diagnoses, random samples of AMI patients were examined for diagnostic criteria for AMI. In both genders, AMI incidence was higher in Gävleborg than in Stockholm (relative risk (RR) 1.34 for men and 1.21 for women) and increased in Stockholm from 1973 to 1981 (RR 1.21 for men and 1.29 for women). The proportion of patients fulfilling the diagnostic criteria for AMI was similar in both areas in 1981 but 10% less in Stockholm in 1981 than in 1973. These results suggest that differences in the validity of hospital discharge diagnoses cannot explain the geographical differences in AMI incidence, but that this may have contributed to the increasing incidence seen in Stockholm county.

Better health--but not for all: the Swedish Public Health Report, 1987

This article is a summary of the Public Health Report submitted to the Swedish Parliament in 1987. Health development, especially that of underprivileged groups, is regarded as an indicator of the quality of social and economic development of the country. Sweden is a very egalitarian country, but in spite of decreasing inequalities in living standards, the Report shows increasing inequalities in health. At the same time, the state has put restraints on health care spending, and the shift in the health care budget toward more primary care has stopped. This development seriously impairs the ability of the health and medical services to cope with inequities described in this Report.