Chapter 5.1: Major public health problems cardiovascular diseases. Centre for Epidemiology, National Board of Health and Welfare, Stockholm, Sweden

Transcription

1 Scandinavian Journal of Public Health, 2006; 34(Suppl 67): Chapter 5.1: Major public health problems cardiovascular diseases MÅNS ROSÉN Centre for Epidemiology, National Board of Health and Welfare, Stockholm, Sweden N Cardiovascular diseases are one of the absolutely largest public health problems in Sweden. The risk of contracting cardiovascular diseases, above all myocardial infarction, declined by about 23% between 1987 and The risk of dying from coronary disease has declined even more by about 40%. N The incidence of stroke remained relatively unchanged between 1987 and 2001, with a certain reduction from Mortality from stroke declined somewhat during the whole of the 1990s. N The risk of contracting and dying from a cardiovascular disease has declined for both genders and all social groups. The large decrease in cardiovascular mortality is the chief explanation of the increasing life expectancy in Sweden during recent years. N Internationally, however, Sweden still has high mortality from coronary diseases compared with other countries in e.g. southern Europe, although cardiovascular diseases have declined considerably more in Sweden than in southern Europe. N Internationally speaking, Sweden has low mortality rates from cerebrovascular diseases even though the risk of having a stroke and the risk of dying therefrom remained relatively unchanged during the 1990s. N Social differences in health and mortality have remained largely unchanged. N There are large social differences concerning mortality from myocardial infarction. Female blue-collar workers run a 60 80% higher risk of contracting or dying from myocardial infarction than female white-collar workers at upper level. A skilled male blue-collar worker runs an approximately 50% higher risk of contracting and dying from myocardial infarction than a male upperlevel white-collar worker. N The differences for people with different educational backgrounds are even greater. N Reduced smoking and lower blood pressure and serum cholesterol levels have contributed to the declining risk of cardiovascular disease. Better treatment methods have been of great significance for the fact that mortality from myocardial infarction has gone down more sharply than the risk of contracting one. Risk factors and causes of cardiovascular disease Over 200 risk factors for cardiovascular disease have been discussed in the scientific literature [1]. Apart from high age and male sex, smoking, high blood pressure and high serum cholesterol are the bestknown and best-established risk factors for coronary diseases including myocardial infarction. For stroke, high blood pressure is the most significant risk factor, but here, too, smoking also involves an increased risk. Diabetes, overweight and obesity, poor social network and difficult social circumstances, e.g. poor economy and increased psychosocial stress also increase the risk of cardiovascular disease. Monotonous and stressful work, with high demands but small possibilities of influencing one s working situation, i.e. small decision-making latitude, Correspondence: M. Rosén, Centre for Epidemiology, National Board of Health and Welfare, SE Stockholm, Sweden. Tel: mans.rosén@socialstyrelsen.se ISSN print/issn online/06/ # 2006 Taylor & Francis DOI: /

2 52 M. Rosén increase the risk of cardiovascular disease [2]. Alcohol abuse gives an increased risk of damage to the heart and blood vessels, while moderate consumption of alcohol among adults can reduce the risk of cardiovascular diseases [3 5]. The present section concentrates on coronary diseases (ischaemic heart disease) of which myocardial infarction is the largest and most serious, and on stroke. Cardiovascular diseases Cardiovascular diseases (diseases of the circulatory organs) comprise diseases of the heart and blood vessels. They include myocardial infarction, angina pectoris, stroke, and others. The chief cause of these diseases is blocked arteries (arteriosclerosis deposits of calcium salts in the blood vessels), giving impaired blood circulation with oxygen shortage (ischaemia) in the body s organs as a consequence. This lack of oxygen can cause incurable damage to the heart and brain. In myocardial infarction part of the muscle tissue in the heart dies owing to lack of oxygen. Assessing the risk of cardiovascular disease Assessing an individual s risk of contracting or dying from cardiovascular disease is not easy since it depends on a number of interacting factors some known, some unknown. In many epidemiological studies, careful health investigations (blood pressure and serum cholesterol measurements etc.) have been made with a large number of people, supplemented with questions on their life situation. Follow-ups have elicited which of those investigated contracted or died from cardiovascular diseases 10, 20 and sometimes 30 years after the first investigation. In this way and on the basis of an individual s risk factor pattern one can establish the absolute risks of contracting or dying prematurely. These longitudinal studies show clearly that some factors are more significant than others for the incidence of cardiovascular diseases. The factors already mentioned, smoking, hypertension and high cholesterol level, are examples of such independent and well-established risk factors, but many others for example hereditary factors, stress, social network are significant too. The risk can also vary depending on whether one lives in the USA, Europe or Asia. It is the aggregate risk factor pattern, rather than individual risk factors, that gives the total risk. This must be the starting point for individual, medical and social action in taking preventive measures. The advantage of assessing absolute risks rather than relative risks is that it gives an idea of the actual risk. The risk of being afflicted by myocardial infarction, for example, is approximately double for a smoker as for a non-smoker, but this tells one little unless the absolute risk for a non-smoker is known. The SCORE study was published recently. The risk of cardiovascular death was calculated on the basis of 12 longitudinal studies in Europe [6]. The study is based on over 200,000 people followed for just over 10 years, and it therefore gives fairly reliable evaluations for the European population. The result is shown in Figure 5:1 and can be read out as a kind scientifically-based horoscope. Note that the study is based only on the three wellestablished risk factors smoking, hypertension and high cholesterol levels, and that it uses mean values only. Individuals may have higher risks (or lower) that deviate sharply from these evaluations, depending on genetic disposition or other risk factors. The examples below give an idea of the risk of dying from heart disease within ten years depending on sex, age, smoking, blood pressure and cholesterol values: N A 50-year-old woman who smokes and has a systolic blood pressure of 180 mm Hg and a cholesterol value of around 5 mmol/l runs a 5% risk of dying from heart disease within 10 years. N A 50-year-old man with the same risk factor pattern, however, runs an almost threefold risk, i.e. 13%, of dying from heart disease within 10 years. N For a 65-year-old man who smokes and who has a systolic blood pressure of over 180 mm Hg and a serum cholesterol value of about 8 mmol/l, the risk is very high on average almost 50%. For a 65-year-old woman, the corresponding risk is just over 20%. N 40-year-olds generally run relatively small risks of dying within 10 years. People who manage to change their risk factors, however, have good prospects of reducing the risks substantially. Many studies have shown, for example, that the risk of being afflicted by myocardial infarction is halved as early as two years after stopping smoking [7]. Individual strategy, population strategy both are needed The reported absolute risks for people with various risk factor levels show that those with more

3 Major PH problems cardiovascular diseases 53 Figure 5:1. Assessment of risk of death from cardiovascular disease within ten years depending on gender, age, smoking habits, blood pressure and cholesterol levels. Source: SCORE project (Systematic Coronary Risk Evaluation), a project between 1998 and 2001 initiated by the European Society of Cardiology (ESC) and financed by the European Union BIOMED-2 programme [6]. concurrent risk factors may run very high average risks of dying from some cardiovascular disease within 10 years. The total number of deaths depends, however, entirely on how many people have this risk factor pattern and, frequently, relatively few people have so many risk factors at the same time; most people run relatively small risks. A 65-year-old man who smokes and has a systolic blood pressure of more than 160 mm Hg and a cholesterol value of more than 6.5 mmol/l runs an average risk of nearly 30% of dying within 10 years (see Figure 5:1). According to data from the northern MONICA studies, 1 however, only 0.5% of men of this age have exactly that high risk pattern [8]. Of the 65-year-old men in Norrbotten and Västerbotten in Sweden, just over 92% are non-smokers, and 27% have a systolic blood pressure under 130 mm Hg. Most of these men run low or moderate risks according to these two parameters. On the other hand approximately 48% of the 65-year-old men in northern Sweden have cholesterol levels over 5.5 mmol/l. The fact that most people run low or average risks means that the largest proportion of deaths will be among these low or average risk people. If many people reduce their risks a little, this can on aggregate save more lives than if a few persons with higher risks reduce their risks considerably. The potential options for a high risk strategy for people with individually high risks on the one hand and a population strategy on the other have been formulated by epidemiologist Geoffrey Rose [9]. Continued reduced risk of contracting and dying from cardiovascular diseases In the whole western world the trend concerning mortality from cardiovascular diseases during the past 30 years has been downwards. In Sweden,

4 54 M. Rosén mortality from these diseases has declined by 44% among men and 54% among women since Of total mortality for 2002, cardiovascular diseases were responsible for 45% of men s mortality and 44% of women s. Men s age-standardized risk of dying from a coronary (ischaemic) heart disease is approximately double that of women s. Of total cardiovascular mortality in 2002, coronary diseases were responsible for 52% among men and 41% among women. Myocardial infarction was responsible for 30% of deaths among men and 23% among women while stroke represented 20% and 27% of the deaths among men and women, respectively. The reduced risks of contracting and dying from coronary diseases are chiefly because tobacco smoking has declined, but the result from the MONICA studies indicate that lower blood pressure and serum cholesterol levels have also had an effect. Better treatment methods, in addition, have meant that those who now contract these diseases are surviving to a larger extent than formerly. That fewer and fewer people contract cardiovascular diseases, predominantly myocardial infarction, is the main explanation of the fact that total mortality throughout the population has declined, with increasing average life expectancy as a result. The risk of contracting and dying from myocardial infarction The risk of contracting cardiovascular disease increases steeply with age. A person who is years old, for example, runs almost a nine-timeshigher risk of contracting myocardial infarction than one of years does. Men have also a considerably higher risk than women of being afflicted by cardiovascular disease. Men aged run a fourfold greater risk of myocardial infarction than women do. Somewhat simplified, women have their myocardial infarctions 10 years later than men, i.e. women s risk is as high as 10-year-younger men s. Female sex hormones, chiefly oestrogen, are thought to protect against heart disease. Hormone replacement therapy has not, however, proved to afford protection against myocardial infarction [10]. Myocardial infarction is the commonest of the cardiovascular diseases. Until the end of 1970s the risk for men of being afflicted by myocardial infarction increased. There has subsequently been a dramatic decrease in both the risk of contracting and the risk of dying from myocardial infarction. While women s risk is at a considerably lower level than men s, the reduction is about as large for women as for men. Moreover, the risk has halved during the past 20 years. Between 1987 and 2001 the incidence of myocardial infarction declined by about 20% (Figure 5:2). Mortality sank even more. The increase in new cases between 2000 and 2001 is explained purely by altered criteria for what is defined as myocardial infarction, so there has been no genuine increase. The risk of suffering and dying from stroke The risk of suffering a stroke was relatively unchanged during the 1990s, followed by a somewhat reduced risk between 1999 and 2001 (Figure 5:3). For mortality, however, there was a slightly decreasing trend from the beginning of the 1990s. The risk of dying within one year of a stroke decreased from about 47% in 1987 to about 39% in Men s risk of suffering a stroke is about 40% higher than the risk of women. Reduced smoking and lower cholesterol levels important explanatory factors The reduction in the number of people who contract cardiovascular diseases for the first time can in all probability be explained by altered living habits chiefly reduced smoking and reduced cholesterol levels throughout the population. This is confirmed by the MONICA-studies. The MONICA studies, from Göteborg, showed that both the number of Figure 5:2. Incidence and mortality rates, respectively, for acute myocardial infarction, per 100,000 men and women for the years (age-standardized). Source: Causes of Death Register and Hospital Discharge Register, Centre for Epidemiology, National Board of Health and Welfare.

5 Major PH problems cardiovascular diseases 55 The fact that mortality has sunk more rapidly than the risk of contracting the diseases indicates that health and medical care have been significant for public health. The risk of dying after a myocardial infarction (lethality) within one year has sunk from 59% in 1987 to 45% in Large social and regional differences Figure 5:3. Incidence rates and mortality rates, respectively, from stroke per 100,000 men and women, (agestandardized). Source: Causes of Death Register and Hospital Discharge Register, Centre for Epidemiology, National Board of Health and Welfare. smokers and cholesterol levels declined between 1985 and 1995, while blood pressure levels increased during that period [11]. The first results from the 2004 MONICA study in northern Sweden were reported recently [12]. They show that average cholesterol levels sank from 6.4 to 5.7 mmol/l in men and from 6.3 to 5.4 mmol/l in women between 1986 and This is a sharp reduction but the levels are still very high by international comparison. The proportion of smokers continues to decrease and in 2004 only 11% of men and 18.5% of women in northern Sweden smoked. As against this, neither systolic blood pressure nor diastolic blood pressure changed noticeably in northern Sweden during the period. Weight and body mass index (BMI) on the other hand have increased sharply among the population of northern Sweden. Since 1986, for example, the proportion of seriously overweight (obesity with BMI 30 or over) has almost doubled. Almost a fifth of the population of northern Sweden are now obese [12]. This increase in northern Sweden is similar to the pattern we see throughout the country. The changes in the risk factor pattern reported above appear largely to tally with how cardiovascular diseases have changed. Decreased smoking and lower cholesterol levels tally well with the fact that the risk of contracting myocardial infarction continues to decrease, and unchanged blood pressure levels tally well with a largely unchanged risk of suffering stroke. The risk of contracting and dying from cardiovascular diseases varies greatly between social groups [12,13]. The skilled blue-collar worker s risk of contracting and dying from myocardial infarction is 50 60% higher than for a man in the upper whitecollar worker group (Figure 5:4). For a non-skilled female blue-collar worker, the risk of contracting myocardial infarction is just over 60% higher than for female upper white-collar workers. Differences in smoking habits and other living habits can explain much of the social difference but other differences in living conditions can contribute to this. Monotonous work with no possibility to affect one s work situation, economy and family circumstances are other factors. The distribution by socioeconomic group in Figure 5:4 has been calculated only for those persons who were included in the population and housing census (FoB) of No FoB has been conducted since 1990 and the details for those included in that FoB are becoming out of date. For this reason we cannot report complete development of myocardial infarction in different socio-economic groups after Figure 5:4. Incidence of coronary disease (including acute myocardial infarction) in men and in women respectively in different socio-economic groups, Source: Sociomedical database, Centre for Epidemiology, National Board of Health and Welfare.

6 56 M. Rosén However, educational level can be used as a social indicator. It turns out that the risk of contracting myocardial infarction is lowest for people with higher education, somewhat higher for those with secondary-school education and highest for them with low education (Figure 5:5). On the other hand, development between 1991 and 2001 is largely the same for all educational levels. For men the risk of contracting these diseases declined by about 20% and mortality by just over 40% for all educational levels. For women the decrease in the risk of having a heart attack was more modest, just 10%, while mortality sank by about 40%. During the 1970s and 1980s in northern Sweden and Värmland a higher risk of incidence and of mortality from coronary diseases than in the rest of Sweden was noted [14]. The causes of these regional differences, which by and large persist, have been discussed and conceivable explanations abound. Presumably, eating habits in northern Sweden have contributed since cholesterol levels there have been considerably higher than in the rest of Sweden. The regional differences in incidence and in mortality have been very stable, certain changed patterns can be seen during the past ten years. For example, Västerbotten and Norrbotten had a sharper decline in mortality than many other counties did, and these counties are now fairly near the national average. This can probably be partly because of energetic preventive efforts in these areas [15]. All Swedish counties have seen a decline in the risk of contracting, and dying from, these diseases; but the development is not equally positive in for example Örebro county, Södermanland, Dalarna and Kalmar counties further south. The regional differences in contracting, and mortality from, acute myocardial infarction, etc., calculated as the average for the years are shown in Figure 5:6. Sweden in an international perspective International comparisons are hampered by the fact that the quality of causes-of-death statistics varies. Such figures must always be interpreted with caution but they can give interesting information on the direction developments are taking. Northern Europe has long been a high-risk area for coronary disease. An analysis of trends in Europe however indicates that these differences are declining somewhat, even though Sweden still has a higher mortality from coronary diseases than countries in, e.g. the Mediterranean area (Figure 5:7). The potential for reducing mortality from coronary diseases should thus still be very great in Sweden. Mortality from myocardial infarction and other coronary diseases, however, is higher than Sweden s in some countries in Eastern Europe, for example Hungary. On average, age-standardized mortality from coronary diseases in Sweden is about 40% above that in the countries of southern Europe. The commonest explanation is that eating habits in the Mediterranean, perhaps primarily the intake of olive oil and other polyunsaturated fatty acids, contributes to the low mortality in these areas [16,17]. There is however no unambiguous explanation and for example heredity and social network may be other factors that contribute. Figure 5:5. Incidence of acute myocardial infarction/coronary disease for populations with differing educational levels, Source: Sociomedical database, Centre for Epidemiology, National Board of Health and Welfare.

7 Major PH problems cardiovascular diseases 57 Figure 5:6. Regional differences (by county) in incidence of and mortality from acute myocardial infarction or other coronary disease as the underlying cause of death, numbers per 100,000 for men and women, average for the years (age-standardized). Source: Statistical Databases, Centre for Epidemiology, National Board of Health and Welfare. Interestingly, Greece has had and still has lower aggregate mortality from coronary diseases than Sweden has. In 2002, age-standardized heart mortality was 30% higher in Sweden than in Greece. For the age groups 65 years and younger among men, however, the situation differs (Figure 5:7). In 1987 mortality among Swedish men aged 65 and younger was 30% higher than among Greek men, while the opposite was true in 2000, when Greek men of these ages had almost 30% higher mortality from coronary diseases than Swedish men had. There is a partly corresponding pattern among women. Hence it appears that remarkable changes and breaks in the development trends are taking place between these countries. A probable explanation is that the proportion of smokers over 15 years of age according Figure 5:7. Mortality rate per 100,000 men and women, respectively, aged 65 and below from coronary diseases in some European countries (age-standardized to the European population). Note that there are different scales for men and women. Source: WHO Mortality Database.

8 58 M. Rosén to WHO is just over 47% among Greek men compared to scarcely 17% in Sweden. Other conceivable explanations can be the health services care of myocardial infarction patients, where Sweden is one of the world leaders. Turning to stroke and other cerebral vascular diseases, Sweden, together with France and the Netherlands, has one of Europe s lowest mortalities. Why are cardiovascular diseases decreasing? The decreased risk of contracting cardiovascular diseases can largely be explained by altered living habits, primarily reduced smoking and partly improved eating habits in the population. A comparison of the risks of contracting acute myocardial infarction in 1987 and in 1995, respectively, shows that an estimated 5,000 fewer Swedes suffered myocardial infarction per year in 1995 [18]. The risk of contracting a myocardial infarction has since continued to decrease even more. Mortality from cardiovascular diseases has decreased more than incidence, which indicates that the health services have also contributed to improved public health. An estimated 3,000 more people per year were saved in 1995 than in 1987 thanks to improved treatment methods [18]. Today, 2005, the numbers who are saved is estimated to be even higher. Note 1 MONICA (monitoring of trends and determinants in cardiovascular disease) is a WHO project that started in Contracting and dying from cardiovascular diseases in different countries is followed over a 10-year period and traditional risk factors are measured during the same period. Sweden has participated with two areas; Göteborg and Norrbotten and Västerbotten [8]. Some of the participating areas, including Norrbotten and Västerbotten, have chosen to continue the study after the end of the 10-year period. References [1] Hopkins PN, RR W. A survey of 246 suggested coronary risk factors. Atherosclerosis 1981;40:1 52. [2] Karasak R, Theorell T. Healthy work. New York: Basic Books; [3] Jackson R SR, Beaglehole R. Alcohol consumption and risk of coronary heart disease. BMJ 1991;303: [4] Fuchs CS, Stampfer MJ, Colditz GA, Giovannucci EL, Manson JE, Kawachi I, et al. Alcohol consumption and mortality among women. N Engl J Med 1995;332: [5] Liao Y, McGee DL, Cao G, Cooper RS. Alcohol intake and mortality: Findings from the National Health Interview Surveys (1988 and 1990). Am J Epidemiol 2000;151: [6] Conroy RM, Pyorala K, Fitzgerald AP, Sans S, Menotti A, De Backer G, et al. Estimation of ten-year risk of fatal cardiovascular disease in Europe: The SCORE project. Eur Heart J 2003;24: [7] Ockene JK, Kuller LH, Svendsen KH, Meilahn E. The relationship of smoking cessation to coronary heart disease and lung cancer in the Multiple Risk Factor Intervention Trial (MRFIT). Am J Public Health 1990;80: [8] MONICA 10 år: Är slaget om hjärt-kärlsjukdomarna vunnet i Norr- och Västerbotten? En sammanfattande rapport över MONICA-projektet i norra Sverige (Has the cardiovasculardisease battle been won in Norr- and Västerbotten? Summary report of the MONICA project in Northern Sweden). Umeå; [9] Rose G. Sick individuals and sick populations. Int J Epidemiol 2001;30:427 32; discussion [10] Behandling mot östrogen: SBU Rapport nr 159, maj Stockholm: (Anti-oestrogen therapy). Swedish Council on Technology Assessment in Health Care (SBU); [11] Wilhelmsen L, Johansson S, Rosengren A, Wallin I, Dotevall A, Lappas G. Risk factors for cardiovascular disease during the period in Göteborg, Sweden. The GOT-MONICA Project. J Intern Med 1997;242: [12] Stegmayr B, Asplund K EM, Janlert U, Messner T. Den svenska riskfaktorprofilen för hjärt-kärlsjukdom : mycket lägre kolesterol, högre BMI, minskad rökning och ökat snusande: Resultat från MONICA projektet (The Swedish cardiovascular-disease risk-factor profile: much lower cholesterol, higher BMI, reduced smoking, increased snuff-taking). Riksstämman Svenska Läkaresällskapet; [13] Peltonen M, Rosén M, Lundberg V, Asplund K. Social patterning of myocardial infarction and stroke in Sweden: Incidence and survival. Am J Epidemiol 2000;151: [14] Rosén M. Epidemiology in planning for health with special reference to regional epidemiology and the use of health registers. Stockholm, Spri; [15] Weinehall L, Hellsten G, Boman K, Hallmans G, Asplund K, Wall S. Can a sustainable community intervention reduce the health gap? 10-year evaluation of a Swedish community intervention program for the prevention of cardiovascular disease. Scand J Public Health, 2001;56: [16] Knoops KT, de Groot LC, Kromhout D, Perrin AE, Moreiras-Varela O, Menotti A, et al. Mediterranean diet, lifestyle factors, and 10-year mortality in elderly European men and women: the HALE project. JAMA 2004;292: [17] Esposito K, Marfella R, Ciotola Mea. Effect of a Mediterranean style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome. A randomized trial. JAMA 2004;292: [18] Rosén M, Alfredsson L, Hammar N. Attack rate, mortality and case fatality for acute myocardial infarction in Sweden during Results from the National AMI Register in Sweden. J Internal Med 2000;248: