Mortality trend due to ischemic heart diseases in the city of Curitiba - Brazil, from 1980 to 1998

Abstracts

OBJETIVO: Analisar a tendência de mortalidade pelas doenças isquêmicas do coração, por sexo, e do infarto agudo do miocárdio, por sexo e faixa etária, de 1980 a 1998, na cidade de Curitiba. MÉTODOS: Utilizou-se os dados de óbitos por doença isquêmica do coração e infarto agudo do miocárdio do Sistema de Informação sobre Mortalidade do Ministério da Saúde, por sexo, faixa etária e local de residência em Curitiba. Os dados de população foram obtidos da Fundação Instituto Brasileiro de Geografia e Estatística. As taxas de mortalidade foram ajustadas por idade pelo método direto, utilizando como referência a população de Curitiba, em 1980. A análise de tendência foi calculada através da regressão linear simples, com um nível de significância de 5%. RESULTADOS: As taxas de mortalidade das doenças isquêmicas do coração apresentaram uma tendência de declínio em ambos os sexos. Nas faixas etárias do infarto agudo do miocárdio, o sexo masculino apresentou queda até os 79 anos; no sexo feminino, até os 59 anos, mantendo-se estáveis após estes períodos. No restante das doenças isquêmicas, o sexo feminino apresentou uma queda maior que o masculino. CONCLUSÃO: O estudo demonstra uma tendência de redução da mortalidade por doenças isquêmicas do coração, em ambos os sexos, na cidade de Curitiba, de 1980 a 1998. No infarto agudo do miocárdio, essa redução vem ocorrendo de forma mais pronunciada nos homens, mantendo-se estável, a partir dos 60 anos, nas mulheres. As razões para a tendência de redução diferenciada entre os sexos não são claras, permanecendo como importante questão para novas investigações.

estudos de tendência; mortalidade; doenças isquêmicas do coração; infarto agudo do miocárdio

ORIGINAL ARTICLE

Mortality trend due to ischemic heart diseases in the city of Curitiba – Brazil, from 1980 to 1998

Edevar Daniel; Helio Germiniani; Eleusis Ronconi de Nazareno; Simone Viana Braga; Anderson Marcelo Winkler; Claudio L. Pereira da Cunha

Universidade Federal do Paraná - Curitiba, PR - Brazil

^{Correspondence}

ABSTRACT

OBJECTIVE: To assess mortality trends due to ischemic heart diseases, per sex, and acute myocardial infarction, per sex and age range, from 1980 to 1998, in the city of Curitiba.

METHODS: Data of death due to ischemic heart disease and acute myocardial infarction from Sistema de Informação sobre Mortalidade do Ministério da Saúde (Information System on Mortality of Ministry of Health), per sex, age range and domicile location in Curitiba were used. Population data were obtained from Fundação Instituto Brasileiro de Geografia e Estatística (Brazilian Institute of Geography and Statistics Foundation). Mortality rates were adjusted per age through direct method, by using the population of Curitiba, in 1980, as reference. The analysis of trend was calculated through simple linear regression, with a significance level of 5%.

RESULTS: Mortality rates due to ischemic heart diseases showed a decrease trend among both sexes. In age ranges of acute myocardial infarction, male sex showed a decrease until 79 years of age, among female sex individuals, the decrease was until 59 years of age. They were shown stable after those periods. Among the remaining ischemic diseases, female sex individuals showed a greater decrease than male sex ones.

CONCLUSION: The study demonstrates a trend of reduction of mortality due to ischemic heart diseases, in both sexes, in the city of Curitiba, from 1980 to 1998. In acute myocardial infarction, such reduction has been happening in a more pronounced way among men, achieving stability, from 60 years of age, among women. The reasons for differentiated reduction trend between sexes are not clear, remaining as na important matter for new investigations.

Key words: trend studies; mortality; ischemic heart diseases; acute myocardial infarction

Circulatory system diseases constitute the main cause of death in the country. In the city of Curitiba, in 1998, they represented 33.8% from total of deaths, being ischemic heart diseases (IHD) and, especially, acute myocardial infarction (AMI), their greatest component¹.

However, despite the magnitude, in the last 40 years, the trend of such taxes has decreased in countries as the United States, Canada, Australia, Japan, the United Kingdom and others of Western Europe, after a practically stationary period².

In Brazil, from the 1970s, some studies have shown the trend decrease of mortality due to ischemic heart disease^3-9. Souza et al., after analysis of mortality due to ischemic heart diseases in the five Brazilian regions, from 1979 to 1996, concluded that the risk of death due to ischemic heart diseases is decreasing in the South and Southeast regions, but increasing in Central-West, Northeast and North regions⁷. Mansur et al., in the analysis of trend of death risk due to circulatory system diseases in Brazil, from 1979 to 1996, demonstrated that there has been a reduction in mortality due to ischemic heart diseases⁸.

For Curitiba, Lolio et al. verified that mortality due to ischemic heart diseases remained stable, in the period from 1979 to 1989, both among men and women⁹. However, the 10-year period, which was assessed, preceded the incorporation of new knowledge on risk factors and intervention, which has been used more and more, such as thrombolytic therapy and primary angioplasty, in addition to new diagnostic and therapeutic advancements that have contributed to a better diagnosis of patients with ischemic heart disease.

Besides those factors, the population of the city of Curitiba has increased in that period. In 1980, the population was 1,024,975 inhabitants; in 1998, 1,550,317, which shows an increase of 51%^10,11. Its age composition also changed, with an increase of aged individuals.

Concerning mortality, in 1980, IHD represented 12.1% and AMI, 7.9% from the total of deaths, whereas, in 1998, IHD represented 12.8% and AMI, 9.0% from total of deaths. By assessing those data, the need for a study along the time (trend), which took into consideration the adjustment of mortality rate per age (age range) was verified.

Within such perspective, this study aimed at assessing the trend of mortality due to ischemic heart diseases, per sex, and to acute myocardial infarction, per sex and age range, from 1980 to 1998, in the city of Curitiba.

Methods

Data from deaths due to acute myocardial infarction and the remaining ischemic heart diseases were available in the Sistema de Informação sobre Mortalidade do Ministério da Saúde (Datasus), per sex, age range and domicile location, in Curitiba, classified in 410-414 (CID-9) and I20-I25 (CID-10) groups^12,13. Population data were obtained from Fundação Instituto Brasileiro de Geografia e Estatística, being sex and age range used as denominators, according to estimates for the period from 1980 to 1998.

Mortality due to acute myocardial infarction was also analyzed per age ranges, between 30 and 80 years old or older, grouped in 10-year intervals, so there would be compatibility with age range classification of deaths shown in DATASUS.

Mortality rates were adjusted per age, through direct method, by suing age range composition in the city of Curitiba, in 1980, as reference.

Rate trend in the study period, per sex and age range, was calculated through simple linear regression and the explainable total variance proportion, through linear method, expressed in R² (it may vary from 1 to 0), being that, the closer it is from 1, it shows a strong trend rate and the closer it is from 0, it shows a weak trend rate. In the equations of straight lines (y=bx+a), which are going to be shown, "x" had the minimum value of 0, in 1980, and the maximum of 18, in 1998. The "b" value, which multiplies "x" in each equation, is the coefficient of straight line incline: the greater "b" module is, the more inclined the straight line is. Negative values of "b" indicate downward inclination (decrease). Hypothesis test were run with a significance level of 5% (p<0.05).

The percentage of yearly variation was calculated from (b/a)x100 rate.

Results

Table I shows mortality coefficients (/100000) per sex, from the total of ischemic heart diseases, which start with 98.4 for male sex individuals, and 62.9, for female sex ones, in 1980, going to 66.1 among male sex individuals, and 43.4, among female sex individuals, in 1998. In acute myocardial infarction, with 70.8 for male sex individuals and 34.4, for female sex individuals, in 1980, and going to 48.3 among male sex patients and 30.3, among female sex ones, in 1998. In remaining ischemic heart diseases, with 27.6 for male sex patients and 28.5 for female sex ones, in 1980, going to 17.7 among male sex individuals and 13.1 among female sex ones, in 1998.

Male/female rate of ischemic heart diseases was kept stable, beginning with 1.6, in 1980, and decreasing to 1.5, in 1998. In acute myocardial infarction, mortality coefficient reduction was more pronounced among male sex individuals, in which male/female rate, which started with 2.1, in 1980, went down to 1.6, in 1998. In remaining ischemic heart diseases, there was a higher decrease trend among women, in which male/female rate, which started with 1.0, in 1980, rose to 1.4, in 1998.

In figure 1, it is verified that ischemic heart diseases showed a significant reduction for both sexes (p<0.05). male sex showed a strong decrease trend (R²=0.76), and the female sex, a medium decrease trend (R²=0.54).

In figure 2, in acute myocardial infarction group, which represents the largest number of deaths, there was a reduction among both sexes (p<0.05), and the reduction was much more pronounced among male sex individuals (R²=0.73) than among female sex ones, which showed a lower reduction (R²=0.29).

In figure 3, in remaining ischemic heart diseases there was a reduction for both sexes (p<0.05). Among female sex individuals, the reduction is medium (R²=0.50), whereas it is lower (R²=0.27) among male sex ones. In specific coefficients of mortality due to acute myocardial infarction, per sex and age range, it was verified that male sex individuals show reduction up to age range from 70 to 79 years old (p<0.05) (figs. 4, 5, 6, 7 and 8), keeping stable in the age range over 80 years old (p>0.05) (fig. 9). Among female sex individuals, it was verified a reduction up to the age range from 50 to 59 years old (p<0.05) (figs. 4, 5 and 6), keeping stable from the age range from 60 to 69 years old to age range of 80 years old and older (p>0.05) (figs. 7, 8 and 9).

Linear straight lines show a decrease trend, whose intensity can be assessed through values of beta, R², p and yearly%. As an example, the equation of total of IHD, among male sex individuals (y=-1.7522 +103.29), says that, from 1980 (x=0), for each change unit in x (from 1 to 16), the rate reduced in -1.7522, on average (starting from 103.29), leading to a decrease trend of the straight line, which shows an R²=0.76 (regarded as strong, as it is close to 1). By expressing in percentage, that yearly reduction was -1.7% (1.7522/103.29x100). the same principle is valid for all other straight lines.

Discussion

Results shown allowed for identifying a reduction of mortality coefficients, adjusted per age, in acute myocardial infarction and remaining ischemic diseases, which shows a reduction of ischemic heart diseases, in both sexes, in the city of Curitiba, from 1980 to 1998.

Such reduction in both sexes can be partly explained by a better contribution of medical care, as well as of primary prevention measures for those diseases, as explanatory variables for the observed decrease of their mortality rates. Goldman and Cook detected that 60% from the decrease of mortality due to ischemic heart disease, observed for the United States, between 1968 and 1976, was related to changes in lifestyle, especially smoking reduction, whereas 40% was due to specific medical interventions on those diseases^14,15.

Among the many studies already carried out in Brazil, the accurate participation of factors involved in the determination of mortality decrease due to ischemic heart diseases ^3-8 is still unknown. The absence of studies for risk or protection factors or for the incidence of that disease, as well as analytical studies that can test their association between mortality, limit desired explanations for the observed decrease.

However, it may be considered, for the city of Curitiba, that the improvement of medical care quality, with an increase of populational coverage by hypertension and diabetes mellitus control programs from Secretaria Municipal de Saúde (Local Health Secretariat)¹⁶, in educational prevention campaigns, in the introduction of new diagnostic resources, coronary units, angioplasties, thrombolysis and myocardial revascularizations must be contributing for a mortality decrease.

Regarding age ranges in acute myocardial infarction, we verified that there was a reduction trend up to the age range from 70 to 79 years old (p<0.05) among male sex individuals, which was kept stable after that period. In female sex patients, we verified a reduction up to the age range from 50 to 59 years old (p<0.05). There was no significant reduction after that period (p>0.05).

Data show that mortality coefficient decrease trend, attributed to acute myocardial infarction, has been occurring in a more pronounced way among men than women, in the age over 60 years old, did not show reduction, which indicated that mortality among men showed a trend of getting closer to mortality rate among women.

Difference in mortality decrease between sexes and the non-reduction of mortality rate after 60 years of age among women, were a clear confirmation in this work. Some studies, after adjustment for all risk and age variables, have showed that in-hospital lethality due to acute myocardial infarction and stable angina is higher among women than among men^17-20.

Among potential explanations, differences between men and women must be considered in the control of coronary risk factors along the time. Men are traditionally recognized as having higher risk. Late arrival after the beginning of chest pains, undervaluation or denial of symptoms, atypical initial clinical records of acute myocardial infarction in women who seek coronary units could be the other possible explanations for mortality difference between sexes.

Unequal hospital handling could also be responsible for the difference between mortality coefficients. It has been described that women are less aggressive approached than men, from the lowest probability of admission in coronary unit to the reference concerning the use of coronary angiography, even that ischemia probability is equal among men and women^21-23. It has been suggested that eligibility of thrombolytic therapy among women with acute myocardial infarction is also done in a differentiated manner. In Western Washington Emergency Department,only 16% form women, against 25% from men were eligible for thrombolysis and, among the eligible individuals, only 55% of women (against 78% of men), had effectively received that medication²⁴.

Another important factor to be analyzed is the presence of a specific biological factor of female sex, maybe with hormonal substrate, which takes place when women enter menopause^25,26. Recognition of such biological fact will lead to the identification of modifiable factors and adjustment of therapeutic conducts, in a way to reduce mortality, after 60 years of age, among female sex individuals.

Another psychosocial and behavioral factors, body mass index, socioeconomic level, frequency of detection and treatment of associated diseases, psychological stress and the behavior of the patient seeking for medical care, could also be contributing for mortality differences between sexes. The study of those factors, as well as the influence from the type of therapeutic intervention and differences of in-hospital lethality of acute myocardial infarction among men and women, represent important matters to be studied in future investigations.

Limitations of healthcare statistics are always present in any mortality study. The quality of proven information in death validation studies and the progressive decrease of deaths classified in the chapter of badly-defined causes, indicate an improvement in information quality. Even with record improvement, it is recommended that the percentage of badly-defined causes should not exceed 10%. In the city of Curitiba, the mean for that group of causes, within the studied period, was 1.1%, which showed a good information quality of basic death causes, supplying reliable data for that analysis¹.

In conclusion, the study demonstrates a trend of reduction of mortality due to ischemic heart diseases in both sexes, in the city of Curitiba, from 1980 to 1998. In acute myocardial infarction, that reduction has happened more pronouncedly among men, keeping stable from 60 years of age in women. In the remaining ischemic diseases, the decrease is higher among women. The reasons for the differentiated reduction trend between sexes are not clear, remaining as an important matter for new investigations.

Even with the demonstration of decrease in mortality rates of ischemic heart diseases, they remain as the main cause of death, deserving a constant and prioritized attention by healthcare and public service professionals in primary and secondary prevention.

References

Received for publishing on 05/23/03

Accepted on 02/23/05

• ¹
  Ministério da Saúde. Datasus. Sistema de Informação sobre Mortalidade – Óbitos por residência e sexo segundo causa no município de Curitiba em 1998.
• 2. Beaglehole R. International trends in coronary heart disease mortality, morbidity, and risk factors. Epidemiolgic Reviews 1990; 12: 1-15.
• 3. Lotufo PA, Lolio CA. Tendência da mortalidade por doença isquêmica do coração no Estado de São Paulo: 1970-1989. Arq Bras Cardiol 1993; 61: 149-53.
• 4. Marcopito LF, Shirassu MM. Mortalidade por infarto agudo do miocárdio e pelas demais doenças isquêmicas do coração no Estado de São Paulo, 1980-96. Arq Bras Cardiol 2000; 75: 69-71.
• 5. Moraes SA, Rezende MHV, Freitas ICM. Tendência da mortalidade por doença isquêmica do coração no Município de Goiânia-Brasil na série histórica entre 1980-1994. Arq Bras Cardiol 2000; 74: 493-7.
• 6. Passos CSP, Lopes AA, Lessa I et al. Tendência da mortalidade por infarto agudo do miocárdio (1981 a 1996) na cidade de Salvador, Brasil. Arq Bras Cardiol 2000; 74: 329-31.
• 7. Souza MFM, Timerman A, Serrano CV et al. Tendência do risco de morte por doenças circulatórias nas cinco regiões do Brasil no período de 1979 a 1996. Arq Bras Cardiol 2001; 77: 562-8.
• 8. Mansur AP, Favarato D, Souza MFM et al. Tendência do risco de morte por doenças circulatórias no Brasil de 1979 a 1996. Arq Bras Cardiol 2001; 76: 497-503.
• 9. Lolio CA, Lotufo PA, Lira AC et al. Tendência da mortalidade por doença isquêmica do coração nas capitais de regiões metropolitanas do Brasil, 1979-89. Arq Bras Cardiol 1995; 64: 213-6.
• 10. Fundação Instituto Brasileiro de Geografia e Estatística. Censo demográfico 1980, Rio de Janeiro, 1983.
• 11. Fundação Instituto Brasileiro de Geografia e Estatística. Censo demográfico 1991, Rio de Janeiro, 1993.
• ¹²
  Brasil. Ministério da Saúde. Datasus. Sistema de Informação sobre Mortalidade (1980-1998).
• ¹³
  Datasus. http://www.datasus.gov.br - Informação direta, 2001.
• ¹⁴
  Microsoft Corporation. Microsoft Excel. 1995 para Windows 95. Excel vs 7.0 Copyrigt 1985-1995.
• 15. Goldman L, Cook EF. The decline in heart disease mortality rates in analysis of the comparative effects of medical intervention and changes in lifestyle. Ann Intern Med 1984; 101: 825-36.
• 16. Secretaria Municipal de Saúde de Curitiba, Boletim Epidemiológico (2000).
• 17. Vaccarino V, Krumholz HM, Berkman LF, Horwitz RI. Sex differences in mortality after myocardial infarction. Circulation 1995; 91: 1861-71.
• 18. Passos LCS, Lopes AA, Barbosa AA, Santos-Jesus R. Por que a letalidade hospitalar do infarto agudo do miocárdio é maior entre as mulheres? Arq Bras Cardiol 1998; 70: 327-30.
• 19. Passos LCS, Lopes AA, Costa U et al. Diferença de letalidade hospitalar da angina instável entre homens e mulheres. Arq Bras Cardiol 1999; 72: 669-72.
• 20. Pimenta L, Bassan R, Potsch A et al. É o sexo feminino um preditor independente de mortalidade hospitalar no Infarto Agudo do Miocárdio? Arq Bras Cardiol 2001; 77: 34-7.
• 21. Kostis JB, Wilson AO, Dowd K and Midas Study Group. Sex differences in the management and long-term out come of acute myocardial infarction. Circulation 1994, 90: 1715-32.
• 22. Clarke W, Gray D, Keating NA et al. Do Women with acute myocardial infartion receive the same treatment as men. Br Med J 1994; 309: 563.
• 23. Maynard C, Althouse R, Cerqueira M et al. Underutilizations of thrombolytic therapy in eligible women with acute myocardial infarction. Am J Cardiol 1991; 68: 529-30.
• 24. Cerqueira MD, Maynard C, Ritchiejl et al. Long-term survival in 618 patients from the Western Washington Streptokinase in Myocardial Infarction Trials. J Am Coll Cardiol 1992; 20: 1452-9.
• 25. Steveson JC, Crook D, Godslnd IF. Influence of age and menopause on serum lipids and lipoproteins in healthy women. Atherosclerosis 1993; 98: 83-90.
• 26. Carvalho ET, Alencar YMG, Liberman S. Fatores de risco de aterosclerose na mulher após a menopausa. Arq Bras Cardiol 1996; 66: 37-48.

Publication Dates

• Publication in this collection
  29 Sept 2005
• Date of issue
  Aug 2005

History

• Received
  23 May 2003
• Accepted
  05 Feb 2005