Trends in coronary events in Finland during 1983–1997; The FINAMI study

V. Salomaaa,*, M. Ketonenb, H. Koukkunenc, P. Immonen-Räihäd, T. Jerkkolae, P. Kärjä-Koskenkarie, M. Mähönena, M. Niemeläa, K. Kuulasmaaa, P. Palomäkib, M. Arstilaf, T. Vuorenmaaf, A. Lehtoneng, S. Lehtoc, H. Miettinenc, J. Torppaa, J. Tuomilehtoa, Y.A. Kesäniemie and K. Pyöräläc

a KTL-National Public Health Institute, Helsinki, Finland
b Central Hospital of North Karelia, Joensuu, Finland
c Kuopio University Hospital, Kuopio, Finland
d Raisio Regional Hospital, Raisio, Finland
e Department of Internal Medicine, Oulu University Hospital and Biocenter Oulu, Oulu, Finland
f University Hospital of Turku, Turku, Finland
g Turku Town Hospital, Turku, Finland

Received May 23, 2002; accepted June 12, 2002 * Corresponding author. Department of Epidemiology and Health Promotion, KTL-National Public Health Institute, Mannerheimintie 166, 00300 Helsinki, Finland. Tel.: +358-947448620; fax: +358-947448338
veikko.salomaa{at}ktl.fi


    Abstract
 Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
Aims To analyse the trends in incidence, recurrence, case fatality, and treatments of acute coronary events in Finland during the 15-year period 1983–97.

Methods and results Population-based MI registration has been carried out in defined geographical areas, first as a part of the FINMONICA Project and then continued as the FINAMI register. During the study period, 6501 coronary heart disease (CHD) events were recorded among men and 1778 among women aged 35–64 years. The CHD mortality declined on average 6.4%/year (95% confidence interval –5.4, –7.4%) among men and 7.0%/year (–4.7, –9.3%) among women. The mortality from recurrent events declined even more steeply, 9.9%/year (–8.3, –11.4%) among men and 9.3%/year (–5.1, –13.4%) among women. The proportion of recurrent events of all CHD events also declined significantly in both sexes. Of all coronary deaths, 74% among men and 61% among women took place out-of-hospital. The decline in 28-day case fatality was 1.3%/year (–0.3, –2.3%) among men and 3.1%/year (–0.7, –5.5%) among women.

Conclusions The study period was characterized by a marked reduction in the occurrence of recurrent CHD events and a relatively modest reduction in the 28-day case fatality. The findings suggest that primary and secondary prevention have played the main roles in the decline in CHD mortality in Finland.

Key Words: Acute myocardial infarction • Coronary heart disease • Case fatality • Epidemiology


    1. Introduction
 Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
The WHO MONICA (monitoring trends and determinants in cardiovascular disease) Project hasrecently documented trends in coronary heartdisease (CHD) events from the early 1980s to the early 1990s, a decade during which major changes occurred in acute coronary care.1–3 Coronary heart disease mortality declined in most westerncountries, while an increase was observed in East European countries. The 28-day case fatality also declined in most countries participating in MONICA, but increased mainly in the same countries where the coronary mortality increased. In the USA, the Minnesota Heart Survey has recently reporteddeclining incidence and recurrence of myocardial infarction (MI) in the population and markedimprovements in the survival of MI patients from 1985 to 1997.4 The Atherosclerosis Risk in Communities (ARIC) study also noted a decline in coronary mortality, but a stable or slightly increasing incidence of hospitalization for MI.5

In Finland, CHD mortality declined steeply during the 10-year period of the FINMONICA Project 1983–1992.6 This was mainly due to declines in the occurrence of first and recurrent CHD events, while the decline in case fatality was modest.6 Marked improvements were observed in acute coronary care as well as in the treatment of chronic CHD.7 Data suggested that the clinical picture of a coronary event could be changing to a less definite and milder direction.8,9

Despite the favourable development, CHD continues to be an important public health problem in Finland, and therefore, to monitor CHD trends, the work of the FINMONICA register has been continued under the name of the FINAMI register. The aim of the present report is to describe the trends in CHD events in residents of the FINAMI areas aged 35–64 years during the 15-year period 1983–1997, thus including 5 years of registration after the closure of the FINMONICA Project.


    2. Methods
 Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
FINAMI is a population-based MI register, i.e. it aims to evaluate all events suspected to be a MI or CHD death among permanent residents of the monitored areas. It follows similar procedures tothe FINMONICA MI register, which have beendescribed.6 The geographical areas covered by the FINAMI register are the town of Turku in southwestern Finland, the town of Kuopio in eastern Finland, the town of Joensuu and some surrounding rural areas in the former province of North Karelia in eastern Finland. Also included in the FINAMI register is the town of Oulu in northwesternFinland. Oulu joined in the project after the closure of the FINMONICA register and currently has data for the years 1993 and 1997. The areas covered by the FINAMI register are urban, with the exception of rural communities around the town of Joensuu in North Karelia. The population of these areas was stable during the study period. In 1995 there were 82 849 men and 87 360 women aged 35–64 years living in the FINAMI areas.

Data for the first 10 years of the present report originate from the FINMONICA MI register and for the last 5 years from the FINAMI register. The primary sources for case finding were the hospital admission diagnoses and death certificates of each area. Trained nurses, supervised by the register physicians, collected the information from hospital documents, death certificates and autopsy reports using data collection forms tailored for laptopcomputers. All relevant hospital documents and autopsy reports were available for the investigators of the FINAMI register. The local registration teams periodically sent their data to the coordinating centre at the National Public Health Institute,Helsinki. There the data were checked for logical errors. Annually the data were further cross-checked with the computerized national Causes-of-Death Register and the national Hospital Discharge Register for completeness. These registers cover all deaths of Finnish residents and every hospitalization in Finland. International Classification ofDiseases (ICD) 9 codes 410–414 and 798, and ICD-10 codes I20–I25 and R96, R98 and I46.1 and I46.9 were used for cross-checking with the national Causes-of-Death register. ICD-9 codes 410–411 and ICD-10 codes I21, I22 and I20.0 were used for cross-checking with the National Hospital Discharge register. ICD-9 was used in Finland until the end of 1995 and ICD-10 thereafter. Events identified through cross-checking and not included in the register were sent back to the local registration teams, which retrieved the necessary documents and evaluated the event according to the study protocol for possible inclusion in the register.

The events were classified on the basis of symptoms, cardiac enzymes, serial Minnesota codingof ECGs, and in fatal cases autopsy findings and history of CHD, into five diagnostic categories:(1) definite MI, (2) probable MI or coronary death, (3) ischaemic cardiac arrest with successful resuscitation, (4) no MI, and (5) fatal unclassifiable events. The classification criteria were the sameas in the FINMONICA MI register and have been described in detail.6,10 Fatal unclassifiable events were cases with no autopsy, no history of typical or atypical or inadequately described symptoms, no previous history of chronic CHD and no other diagnosis. There were very few such events (, 0.5% of CHD events). For the analyses and presentation we defined FINAMI CHD mortality as the sum of fatal events in categories 1, 2, and 5, i.e. fatal definite MIs, probable coronary deaths, and fatal unclassifiable events. FINAMI CHD events weredefined to include both fatal and non-fatal events in categories 1 and 2, and fatal events in the category 5, i.e. fatal and non-fatal definite MIs, probable non-fatal MIs and coronary deaths, and fatal unclassifiable events.

Creatine kinase (CK)-MB-mass assay partlyreplaced the old CK-MB isoenzyme determination during the last year of the study (1997), but troponins were not yet used during the present study. The frequency of autopsies was high in the FINAMI areas. Among men, on average 50, 63, 80, and 67% of fatal cases were autopsied in Joensuu area, Kuopio, Turku and Oulu, respectively. Among women, the respective proportions of autopsied cases were 50, 65, 77 and 36%. The autopsies were specifically directed to cases of death whichoccurred out of hospital, where the clinicalinformation was often scarce.

The period of one event was 28 days, during which the most severe findings were recorded. If the symptoms recurred more than 28 days after the index event, they were considered to belong to a new event. The event was considered to be incident (=first ever for the particular patient) if there was no indication of a previous, clinically recognised MI in the patient's history, otherwise the event was considered as recurrent. The 28-day case fatality was defined as the proportion of fatal events from all events. The prehospital case fatality was defined as the proportion of events in which the patients did not reach a hospital alive or died within one hour after the onset of symptoms, from all events. The 28-day case fatality of hospitalized events was defined as the proportion of events in which the patients were hospitalized alive and had survived for more than 1h after the onset of the symptoms but died within the 28-day period, of all those events in which the patients were hospitalized alive and had survived at least for 1h after the onset of symptoms.

Information on revascularization procedureson the MI patients was collected during the last10 years of the study, 1988–1997. The questionincluded both revascularizations actually performed within 28 days after the onset of symptoms and decisions made during the 28-day period to perform a revascularization.

2.1. Statistical methods
Coronary event rates were expressed per 100 000 persons and age-standardized according to thedirect method using 5-year age groups and the European standard population as the standard.11 The annual population counts for the denominators were obtained from the National PopulationRegister, which is updated continuously. The 95% confidence intervals (CIs) for the event rates were calculated assuming Poisson distribution for the annual numbers of events. The 28-day case fatality was age-standardized using weights derived from the combined age distribution of MI and stroke patients in the WHO MONICA Project.1 The trends in event rates and case fatality were determined, as described earlier,6 using log-linear Poisson regression models with the year as independent variable. The regression coefficient of year multiplied by 100 gives the average annual change in percents. Second-order terms for the year were tested to assess deviations from linearity. These were significant for recurrent events only. Accordingly, a linear trend is reported for incident events and for mortality. For recurrent events, however, the change over the total 15-year period is reported, together with annual average changes for three separate periods, 1983–87, 1987–92, and 1992–97, calculated as a continuous, piecewise linear curve. Oulu was excluded from the trend analyses, because it had data for the years 1993 and 1997 only. Because the trends in the other FINAMI areas were similar, results based on pooled data are presented for simplicity and to reduce the random fluctuation. The statistical analyses were carried out using SAS.12


    3. Results
 Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
During the study period, 6501 CHD events were recorded among men and 1778 among women aged 35–64 years. Of these events 4360 (52.7%) were definite, 3877 (46.8%) probable, and 42 (0.5%) fatal unclassifiable CHD events. Table 1 presents by area the age-standardized CHD mortality according to the official mortality statistics and according to the FINAMI register, and the incidence of first CHD events during the last 5-year period of the study, 1993–97. CHD mortality in the FINAMI register was very close to the CHD mortality obtained from the official mortality statistics for each area and both genders. Both incidence and mortality were higher in the eastern areas, Joensuu and Kuopio, than in the western parts of the country, Turku and Oulu.


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Table 1 Age-standardized CHD mortality and incidence of myocardial infarction events (per 100 000 inhabitants, 95% confidence interval in parenthesis) in the FINAMI areas during 1993–97abased on official mortality statistics and FINAMI Register

 
During the 15-year study period the average annual decline in CHD mortality in the FINAMI areas was 6.4%/year among men and 7.0%/year among women (Table 2). The incidence of first events also declined significantly, but somewhat less than mortality, 4.0%/year among men and 3.9%/year among women. A non-linear accelerating decline wasobserved in the occurrence of recurrent events. The second-order term for year was significant both for men and for women . When calculated as a continuous, piecewise linear curve, the annual average decline among men was 2.8% for the period 1983–87, 8.5% for the period 1987–92, and 12.1% for the period 1992–97. Among women, an increase of 1.9%/year was observed for the first period, after which declines of 10.2 and 13.8%/year followed for the two latter periods. The decline in mortality from recurrent events was also steep, 9.9%/year (95% CI –8.3, –11.4%) among men and 9.3%/year (95% CI –5.1, –13.4%) among women. The proportion of recurrent MI events of all MI events was higher in men than in women anddeclined significantly in both genders (Fig. 1).


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Table 2 Age-standardized ratesaand trendsbin CHD mortality and first and recurrent myocardial infarction events in the population aged 35–64 years of the FINAMI areas

 


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Fig. 1 Trends in the proportion of recurrent events of all MI events among men and women aged 35–64 years in the FINAMI areas. The average annual relative change was –2.6%/year (95% CI –1.6 to –3.6%, ) among men and –3.7%/year (–1.6 to –5.9%,) among women. The average proportion is higher among men than among women (, adjusted for age and study area).

 
The 28-day case fatality of coronary eventsdeclined significantly 1.3%/year among men and 3.1%/year among women (Table 3). We further divided the 28-day case fatality to prehospitalcase fatality and to the 28-day case fatality of hospitalized events. On average, 74% of all fatal events among men and 61% among women were prehospital, i.e. only 26% of men and 39% of women who died within the 28-day period reached ahospital alive. Prehospital case fatality declined non-significantly at 1.0%/year among men, whereas among women the decline was 4.0%/year, which was statistically significant. The 28-day casefatality of hospitalized events declined significantly at 2.7%/year among men. Among women, there was a non-significant decline of 3.0%/year. In Oulu, the average 28-day case fatality of coronary events during the period 1993–97 was similar to the other areas of the FINAMI study, 33.7% among men and 24.7% among women. As a whole, the 28-day case fatality of coronary events was significantly higher among men than among women (, adjusted for age and study area). This was due to the fact that the prehospital case fatality was clearly higher among men than among women, whereas the 28-day case fatality of hospitalized events was similar in both sexes (Table 3).


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Table 3 Age-standardized 28-day case fatality, prehospital case fatality, and 28-day case fatality for hospitalized cases during 1983–1997 among persons aged 35–64 years in the FINAMI areas

 
The proportion of revascularizations remained low until the early 1990s and consisted mainlyof coronary artery bypass grafting (CABG), but increased after that and included an increasing proportion of percutaneous transluminal coronary angioplasties (PTCAs) (Fig. 2). During the last study year, 1997, the proportion of revascularizations reached 25% among men and 16% among women and approximately half of them were PTCAs. Oulu (not included in the figure) adopted PTCAs more actively than the other FINAMIcentres. In 1997, 24% of men and 17% of women, who reached hospital alive and remained alive for at least 1 day after the beginning of symptoms, received PTCA and a further 18% of men and 4% of women received CABG in Oulu. During the last 5-year period of the study, 1993–97, men received revascularizations significantly more often than women (, adjusted for age, study area, and study year).



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Fig. 2 The proportion of coronary artery bypass grafting (CABG) or percutaneous transluminal coronary angioplasties (PTCA) performed or decided to be performed during the 28-day period after the onset of symptoms on patients aged 35–64 years hospitalized alive with definite or probable MI.

 
Data on thrombolytic treatment for the years 1993–97 and medications prescribed at discharge from hospital after MI are shown in Fig. 3. Among men, who reached the hospital alive and survived at least 1 day after the onset of the event, thrombolytic treatment of definite and probable MIs increased from 27 to 37% during 1993–99, but declined slightly during 1997. Among women, thrombolytic treatment increased steadily from 16% in 1993 to 22% in 1997. In Oulu (not included in the figure), 50% of men and 26% of women received thrombolytic treatment in 1997, which reflected the more active treatment practice patterns of MI in Oulu than in the other FINAMI areas. On average, during the period 1993–97, women receivedthrombolytic treatment significantly less often than men (, adjusted for age, study area, and study year). At discharge, beta-blockers and acetyl salicylic acid (ASA) were commonly prescribed both for male and female MI patients. ACE-inhibitors were prescribed to approximately one third of MI patients. Prescriptions of lipid lowering medications increased clearly: among men from 14% in 1994 to 40% in 1997 and among women from 13% in 1994 to 45% in 1997.



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Fig. 3 The proportions of patients aged 35–64 years hospitalized alive with definite or probable MI receiving thrombolytic treatment at the acute stage and/or a prescription of beta-blockers, acetyl salicylic acid (ASA), ACE-inhibitor and/or hypolipidemic medication at discharge.

 

    4. Discussion
 Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
Several centres, which participated in the WHO MONICA Project have continued MI registration, often with a somewhat modified protocol. To our knowledge, this is the first study reporting data for a substantial post-MONICA period. This reportdemonstrated that in Finland the rapid decline in coronary mortality, which we have reported earlier for the period 1983–92,6 has continued during 1993–97. As a whole, this 15-year period was characterized by the steep decline in the occurrence of recurrent coronary events. The incidence of first events also declined, but the decline in 28-day case fatality remained relatively modest.

Coronary mortality rates in the FINAMI-register were very similar to those in the official mortality statistics, thus confirming the reliability of official mortality statistics in Finland, consistent with our earlier report.13 Declining trends in coronary mortality in the Finnish centres were among the steepest in the WHO MONICA Project.1 Due to possible methodological differences, comparisons with other populations need to be done with caution. In the ARIC communities in the USA, coronary mortality declined during 1987 to 1994 by 4.7%/year among white men and by 4.5%/year among white women aged 35–74 years.5 In Minneapolis/St Paul area the coronary mortality of persons aged 30–74 years fell during the 12-year period 1985–97 by 47% among men and by 51% among women.4 A recent report from Sweden has described a reduction of 30% in mortality from MI among men and women aged 30–64 during 1987–95.14 Against this background it seems that the average annual declines of 6.4% among men and 7.0% among women in Finland are at least as steep as the declines in the USA and steeper than the declines in Sweden.

The WHO MONICA Project did not report trends in the incidence of first coronary events, but the steepest decline in the attack rate, including both first and recurrent events, of MI among men was observed in North Karelia, Finland, followed by Kuopio, Finland.1 Also, among women, the declines in the attack rate of MI in the Finnish centres were among the steepest of the MONICA centers.1 Incidence trends have been reported from MONICA centres in New Zealand and Australia.15 Among men, the annual average declines in incidencewere 3.0, 4.9, and 1.6% in Auckland, New Zealand, Newcastle, Australia, and Perth, Australia, respectively. Among women, the corresponding annual average declines were 1.7, 5.4 and 1.1%. In the ARIC communities the incidence of first myocardial infarction or death due to CHD declined by a non-significant 1.9%/year among white men and 2.1%/year among white women.5 In Minneapolis/St Paul the incidence of hospitalized definite MI declined by approximately 10% during 1985–97.4 In the Swedish study, which is based on the linkage of the hospital discharge register and the national death register, incidence of first events is not givenseparately, but the attack rate in persons aged 30–64 years declined by 3.0%/year in men and by 1.4%/year in women. In the present study, we found the annual average declines in incidence of 4.0%/year among men and 3.9%/year among women. Despite the methodological and age group differences it seems that the incidence of first coronary events is declining in Finland at a pace, which is among the fastest in the world. An interesting common feature in the studies, whichreported data on the incidence of first events, was that the decline in incidence was smaller thanthe decline in mortality. In FINAMI areas, the 95% confidence intervals of CHD mortality trend and incidence trend did not overlap among the men, and among the women the overlap was only slight. This suggests that the prevalence of persons who have survived an MI event is increasing. Thisphenomenon may in part explain why in somecountries hospitalizations for CHD other than MI have increased substantially.16

We have shown earlier that the decline in the occurrence of recurrent coronary events contributed importantly to the decline in coronary mortality in Finland during 1983–92.6 The almost 10% annual decline in mortality from recurrent events in the present study is in agreement with this earlier finding and with other literature.4 Two interesting new features emerged from the present analyses: the curvilinear accelerating shape of the decline in the occurrence of recurrent coronary events, and the decline in the proportion of recurrent coronary events of all events. Very few other studies have analysed trends in recurrent events and, to our knowledge, these features have not been reported previously. In the Minneapolis/St Paul area, recurrence rates fell 20–30% during 1985–97, which is two to three times as much as the reported decline in the incidence of hospitalized MI.4 The rapid reduction in the occurrence of recurrent events indicates successful secondary prevention measures among patients who have survived the initial 28-day period.

In the WHO MONICA Project, the 28-day case fatality trends in Finnish centers were not among the most favourable ones.1 When the 15-yearperiod of the present study was considered, amodest but significant decline was observed both among men and among women. The ARIC studyhas reported a decline in the overall 28-day case fatality of 3.9%/year among men and 6.1%/year among women.5 The Minnesota Heart Surveyreported declines both in out-of-hospital andin-hospital coronary deaths.4 For hospitalized cases the odds ratio of 28-day mortality in 1995 compared to 1985 was 0.48 among men and 0.64 among women. In Sweden, no improvement was observed during the first day of the attack, but the overall 28-day case fatality improved from 30 to 23% among men and from 28 to 23% among women.14 Though comparisons between different studies should be done with caution, it seems likely that the improvement in case fatality of MI events in Finland has remained more modest than in many other western countries.

A comparison of the acute coronary care data from the FINAMI areas with published data from Minnesota4 and from MONICA centres3 suggests that revascularizations and in particular PTCAs have been used in Finland less often than in the USA and in many other countries. A recent report from the Technological Change in Health Care (TECH) Project also suggested that the availability of PTCAs in Finland has been fairly limited compared to most other countries participating in the Project.17 On the other hand, the medical treatments,thrombolysis, beta-blockers, and ASA have been commonly administered to MI patients in the FINAMI areas. The use of lipid lowering treatments was low but increased rapidly during the last years of our study. These findings are in agreement with the results of the EUROASPIRE II survey.18,19 It is likely that the widespread use of beta-blockers and ASA for secondary prevention has contributed to the decline in the occurrence of recurrent events and to the decline in the mortality from recurrent events. Whether the limited availability of acute revascularization services has hindered more substantial improvement in case fatality is an interesting question. In Oulu, where PTCAs have been used more actively than in the other FINAMI centers, the 28-day case fatality was not different from the other centres.

In the FINAMI areas, 74% of all coronary deaths among men and 66% among women occurred out-of-hospital. This emphasizes the importance ofprimary and secondary prevention in the efforts to reduce coronary mortality, since the large majority of events cannot be helped by hospital care. It is obvious that primary and secondary prevention have played the main roles in the decline of coronary mortality in Finland during this 15-yearperiod 1983–97. The improvement in CHD riskfactor levels in the Finnish population has been well documented.20 It has also been estimated that until the mid-1980s changes in risk factors explained almost all of the change in coronary mortality, but thereafter the observed decline in mortality was faster than that predicted on the basis of risk factor changes alone.21 The most likely reason for this difference is the improved treatment. Severalstudies have shown the substantial impact of medical treatments on coronary mortality rates in population.22,23 Our data are in agreement with these studies and suggest that in Finland the treatment of chronic CHD has been the main contributor while the treatment of acute MI has played a smaller role.

A limitation of our study was that Turku, Oulu, Kuopio and the town of Joensuu are all urban areas. A few communities around the town of Joensuu were the only rural areas included in the study. Since the coronary mortality and morbidity tend to be higher in rural than in urban areas, our study may give a slightly too optimistic view on the CHD situation in Finland. The trends in CHD mortality have, however, been similar in FINAMI areas as in the whole country. Another limitation was that these 15-year trends were available for the age group 35–64 years only. Therefore, our resultscannot be taken as representative for the total population of Finland. Since 1993 we have registered coronary events also in persons aged ≥65 years. In due course these data will tell us, whether the mortality and incidence of coronary events are declining also in older individuals.

In conclusion, the favourable development in coronary mortality has continued in Finland. The 15-year period 1983–97 was characterized by a marked reduction in the occurrence of recurrent coronary events, a substantial reduction in the incidence of first events and a relatively modest reduction in the 28-day case fatality. These findings suggest that primary and secondary prevention have played important roles in the decline of CHD mortality in Finland, whereas the role of acute coronary care seems to have been smaller.


    Acknowledgments
 
The study was supported by the Finnish Foundation for Cardiovascular Research.


    References
 Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 

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