Coronary Heart Disease Trends in Australia and the Associated Risk Factors
Coronary heart disease (CHD) remains the prime reason of death in Australia. Over the past 30 years, there has been a steady regression in the mortality rate related to CHD. Nevertheless, this is a leading cause of death in Australia that has claimed nearly 26,521 lives in 2000 (Mathur, 2002). During the twentieth century this has been the utmost epidemic in Australia. Mortality rates due to CHD was at its highest in the late 1960s, but since then death rates have declined by 60%, nevertheless it is still a trivial health problem in the country. CHD is a major challenge, also in the other developed countries of the world. Murray and Lopez (1996) estimate that every year 6.9 million people worldwide succumb to this disease. From the present trend, it is predicted that by 2020 CHD will become the sole and chief public health problem across the globe (Murray and Lopez 1996).
Coronary heart disease not only result in death, but also brings associated illness, disability, poor quality of life and premature mortality, and in Australia direct healthcare costs associated with CHD surpass those of any other disease (Mathur, 2002). The overall health status of people who had cardiovascular disease was much inferior to without a cardiovascular disease (Australian Bureau of Statistics, 2006b). In addition, of the people with cardiovascular disease, 12% also had diabetes, 39% also had arthritis and 14% also had a mental and behavioral health problem (Australian Bureau of Statistics, 2006b).
The fundamental risk factor to CHD is cardiovascular disease (CVD), predominantly atherosclerosis. This is a process related to abnormal deposit of fat, cholesterol and other substances (plaque) in the inner lining of the arteries. Risks of angina and stroke are much greater in individuals with atherosclerosis (AIHW 2004). Other associated cardiovascular conditions include angina, other ischemic heart disease, cerebrovascular diseases, edema and heart failure, diseases of arteries, arterioles and capillaries.
Incidence and Mortality
CHD incidence is a central marker in discerning the impact of lifestyle changes and treatment and technology advancements. According to Mathur (2002), in 1999 to 2000, there were about 48,313 CHD events in Australia among 40 and 90 year-olds. 29,731 were among men and 18,582 were among women. The study also reports incidence rates for CHD to be declining over the last decade. Rates have been steadily falling around 20% among 40 to 90 year-olds between 1993 to 1994 and 1999 to 2000. From an initial number of 50,611 in 1993 to 94, the number has dropped down to 48,313 in 1999 to 2000. However, during 1999 to 2000, men were twice vulnerable to a coronary event as women and with incidence rates for men were much higher than women across all age groups. Similarly, incidence rates during 1999 to 2000 were about eight times greater among men aged 75 to 90 years than those of 40 to 64 year-olds, indicating that age is an important factor influencing CHD incidence. It is also obvious that men usually suffer from heart disease at a younger age than women.
Mortality due to CHD was the largest single cause of death in Australia in 2000. Death toll was 23,012 among 40 to 90 year-olds, among which 13,034 were men and 9,978 were women. This estimates to a mortality rate of 285 deaths per 100,000 populations (Mathur, 2002). A substantial regression in CHD death rates has been witnessed in Australia; decline to be by over 60% (AIHW 2002a). A comparative study of death rates across OECD countries between 1987 and 1997 reveals that death rates decline in Australia was one of the largest with 36% decline. Decline in Denmark was by 38%, while in Luxembourg 35%, New Zealand 36% and Norway 34%. In the United States and Canada, mortality rates were slower as compared with Australia (26% and 32% respectively) (OECD 2001).
A survey conducted in Australia through 1950 to 2000 showed that incidence and mortality was continually on the rise and was at its peak during late 1960s. However, the trend has been vice-versa thereafter with a steady decline. Interesting, incidence rates were much higher in men as compared to women for both coronary heart disease and cardiovascular disease as well (Stevenson, 2006). Another study conducted in Australia between 1986 and 1996 showed that mortality from CHD regressed by 46% in men and 51% in women. This number was for 61% of the decline in mortality from all risk factors associated with CHD in men and 48% in women (Sexton and Sexton, 2000).
Death rates for Coronary heart disease and cerebrovascular disease, 1950 to 2004
(Source: Stevenson, 2006).
Mathur (2002) estimated mortality rates among the population aged 40 to 90 years. It was evident that CHD death rates have declined by 59% for men and 55% for women between 1980 and 2000. The number fell from 29,510 in 1980 to 23,012 in 2000. In 2000, CHD took toll of greater number of lives of men than women. Interestingly, mortality rate for men of belonging to age group 40 to 90 years was 332 deaths per population of 100,000, while for the women it was 241 deaths per population of 100,000. The study also suggested that over the last two decades, mortality rate among men has been higher than women and this has remained consistent. In addition, mortality rates for age group 75 to 90 years were significantly higher than for 40 to 64 year old people, indicating that death rates for CHD showed a marked increase with age and men tend to die from CHD at an earlier age than women.
Cardiovascular disease, an associated problem also takes toll of several lives. Mortality rate for CVD in Australia was 47,637 or 36% of deaths in 2004 (ABS 2006a). Highest numbers of deaths were associated with ischemic heart disease and cerebrovascular disease. In 2004, ischemic heart disease proved fatal in 19% of males and 18% of in females. Stroke, the second most common cause of cardiovascular death has claimed 7% of lives in males and 11% in females in 2004 (ABS 2004a). However, a declining trend has been observed also for cardiovascular diseases. In 2003, death rates declined by 39% for CHD for both men and women and 32% for men and 31% for women for cerebrovascular disease (Stevenson, 2006).
Geographical region and socioeconomic status also tend to play a significant role in CHD. Death rates significantly vary among different groups of Australian population. The Aboriginal and Torres Strait Islander peoples and people of lower socioeconomic groups show higher CHD death rate (AIHW 2001) and this has been an issue of concern in Australia. Australia’s Health 2002 (AIHW 2002a) recognized some of the core causes for the higher liability of CHD among these people groups in Australians.
Risk factors associated with coronary heart disease
Reducing the levels of biomedical and behavioral risk factors, and improving the use of effective drug treatments has the potential to lead to large reductions in coronary event rates (McElduff et al. 2001). However, the risk tends to remain. Several factors contribute to pose CHD risk; these are lifestyle, behavioral and dietary factors such as high blood cholesterol, high blood pressure, overweight and obesity, tobacco smoking, insufficient physical activity and diabetes. These risk factors are further more influenced by other factors such as people’s economic resources, education, living and working conditions, social support, and access to healthcare and social services and by psycho-social factors as well (AIHW 2001 and AIHW 2002a).
High blood cholesterol
It was estimated that in 1999 to 2000, over six million Australians aged 25 years and over had total blood cholesterol levels higher than 5.5 mmol/L. Rates were alike in men and women. Studies show that high blood cholesterol increases with age and men aged 45 to 64 years and women aged 55 to74 years were twice as likely to have high blood cholesterol levels as those aged 25 to 34 years (Mathur, 2002). However, since 1980, there has been no significant decline in the occurrence of high blood cholesterol. A survey conducted by Australian Bureau of Statistics in 2006 showed that between 2004 and 2005, 7% of the population has high blood cholesterol. For those above 65 years of age the percentage was still higher, about 22% (ABS, 2006b). The report also reveals that 40% of Australians reporting a cardiovascular condition have high blood cholesterol.
High blood pressure and Hypertension
In 1999 and 2000, 3.6 million Australians aged 25 years and above had high blood pressure (140/90 mm Hg) (Mathur, 2002). Of this 31% were men and 26% were women. Studies also reveal that the prevalence of high blood pressure is directly proportional to age. From less than 8% among 25 to 34 year old people, the level increases to over 70% among those aged 65 years and over. However, with treatment the rates can be brought down and since 1980s average blood pressure levels have declined greatly. This can be further influenced by greater availability of low-salt products in the food supply (AIHW 2002a). Hypertension is another factor. Data from the 2004 to 2005 NHS showed an augmented incidence rates for hypertensive disease. Every year 3% of the adult population contract hypertensive disease with the risk increasing from 1% for those aged between 25 and 34 years to 8% for those aged between 65 and 74 years (IDI 2006).
Overweight and obesity
Overweight and obesity are factors closely associated with coronary heart disease, heart failure, stroke, high blood pressure and high blood cholesterol (AIHW 2004). A survey conducted across Australia in 1999 and 2000 revealed that 7.5 million people aged 25 years and over were overweight or obese (60%). This included 67% men and 52% women. In 2004 and 2005, according to their proportionate height and weight, 34% of persons aged 15 and over years were overweight, and 17% were obese. It is also obvious that the proportion of overweight and obese Australians is yet on the rise. In 1995, 39% of persons aged 15 years and over were reported to be obese, the number increased to 44% in 2001 and furthermore to 47% in 2004 to 2005. 63% of obese people aged 15 years were with cardiovascular disease and 48% of obese people were without cardiovascular disease (63% compared with 48%). Similarly 65% of obese Australians aged 15 years and over were reported to have heart, stroke and vascular diseases and 51% of obese people were those without heart stroke and vascular disease (Australian Bureau of Statistics, 2006b).
Diabetes causes an increased risk for developing coronary heart disease, stroke and peripheral vascular disease (AIHW 2004). Predominantly, Type 2 diabetes has been the risk factor for coronary heart disease and is believed to double increase the risk of a fatal event (Fuller et al., 1983). In 1999 and 2000, 938,700 Australians aged 25 years and over had diabetes. This accounts to about 7.5% of the population (Mathur, 2002). In addition, 11% showed impaired glucose tolerance. Results from the 1981 Busselton Population Survey and the 1999 to 2000 Australia Diabetic study puts forward that over the 20-year period the rate of diabetes may have doubled in Australia (AIHW 2002b). A survey conducted between 2004 and 2005, showed 60% of people reporting diabetes to also have CHD and cardiovascular diseases (Australian Bureau of Statistics, 2006b).
Tobacco smoking not only increases the risk of coronary heart disease, stroke, and peripheral vascular disease but also caused a range of cancers and other diseases (AIHW 2004). Men aged 18 years and over were more likely to smoke regularly than women of the same age (21% and 18% respectively) (Mathur, 2002). Smoking rates have been declining since the 1950s, when it was estimated that around 70% of men and 30% of women smoked.
Since 1985, smoking rates have continued to (AIHW 2002a). The proportion of adults who are current smokers has considerably changed over time with number coming down from 24% in 2001 to 23% in 2004 and 2005. 15% of adults reporting cardiovascular disease and CHD were reported being a current daily smoker. 39% ex-smokers also reported to suffer from these diseases (Australian Bureau of Statistics, 2006b). Among smokers less than 65 years of age, 67% of ischemic heart disease in Australian men and women can be attributed to cigarette smoking (Ridolfo and Stevenson, 2001).
Insufficient physical activity
Trends reveal that during the 1980s and much of the 1990s there was very little change in patterns of physical activity. Nevertheless, between 1997 and 2000, rates of physical inactivity among Australians increased significantly from 38% in 1997 to around 43% in 1999 and 2000 (Bauman et al. 2001). Data from the 2001 and 2004 to 2005 surveys has shown that rates of physical inactivity were highest among 45 to 64 year-olds and lowest among 18 to 24 year-olds. More than 15% of people showed no leisure-time physical activity and around 28% did some activity (AIHW 2002a).
Higher risk factors and multiple risk factors influencing CHD in Australia
Factors such as socioeconomic and cultural largely influence the health of individuals and Populations. The lower socioeconomic populations and Aboriginal and Torres Strait Islander Australians have much greater risk to CHD than other Australians. This may be because they are likely to smoke tobacco, be physically inactive, be obese, have high blood pressure, be obese and have Type 2 diabetes than other Australians (AIHW 2001).
A survey conducted across Australia showed that in 1995, about 81% of the adult population had at least one major modifiable risk factor such as tobacco smoking, high blood pressure, overweight and obesity, or physical inactivity (Mathur, 2002). Of these, 43% of adults had two or more of these risk factors and 13% had three or more risk factors. Furthermore, multiple risk factors are far more prevalent among older Australians than younger Australians. Almost two-thirds of people of 75 years age and over have at least two risk factors compared with 30% of men and 22% of women aged 18 to 24 years. Metabolic syndrome is the reason behind the multiple risk factors. The metabolic syndrome is a collection of interrelated risk factors such as high cholesterol, high blood pressure, hypertension, obesity and diabetes (AIHW 2002a). In a study comparing CHD incidence among aboriginal and non-Aboriginal Australians, overall there was a pattern of augmented risk for CHD. This was primarily related to drinking at higher levels with the lowest risk in the group drinking at ‘safe’ levels (National Health and Medical Research Council, 2001), coherent with a J-shaped relationship as described in other populations (Corrao et al., 2000).
Treatment for CHD
Substantial decline in incidence and CHD mortality can be attributed to declines in some of the major risk factors and medication use. Recent evidence from studies conducted with randomized controlled trials has shown that bringing down levels of cholesterol and blood pressure will significantly reduce coronary events (McElduff et al. 2001). A versatile range of effective drugs are available to reduce the occurrence of atherosclerosis and high blood pressure which are the prime factors in the prevention and treatment of people with CHD.
Blood pressure lowering drugs
These are ‘blood pressure lowering’ drugs used to treat varied conditions as well as high blood pressure or heart failure. This includes the ACE inhibitors, beta blockers, calcium channel blockers and diuretics (AIHW 2001). Between 1990 and 1998, administration of Angiotensin-converting enzyme (ACE) inhibitors increased three times and the highest increased was recorded for the early 1990s. Increase was twofold between 1991 and 1994. However, since then the consumption of ACE inhibitors between 1995 and 1998 has increased gradually by around 27% (Mathur, 2002). Treatment with ACE inhibitors after discharge was also estimated to be around 30–35% (AIHW: McElduff et al. 2000). Between 1985 and 1987 and 1991 and 1993 there was considerable rise in use of ACE inhibitors before and during the coronary event admission. The rise is primarily attributed to the use of this drug during the admission.
Drugs such as beta blockers are used to decrease pain and death in people with a record of angina and a previous history of heart attacks and calcium channel blockers are used enhance blood vessels to dilate and thus effective in reducing blood pressure and angina.. Survey conducted between 1990 and 1998 showed that the use of beta blockers was maximum in 1990; the number gradually regressed by 1994 and thereafter remained steady. The usage of calcium channel blockers has risen steadily in the 1990s. Usage almost doubled between 1990 and 1998 (24.3 DDD/1,000/day in 1990 to 46.5 DDD/1,000/day in 1998) (Mathur, 2002).
Diuretics which are effective in reducing blood pressure also assist in the dilation of blood vessels and can be a useful drug in the treatment of CHD. These are often used in combination with other drugs, usually ACE inhibitors for treating people with cardiovascular disease (56.2 DDD/1,000/day in 1998). Mathur (2002) revealed that over the last decade use of diuretics has come down gradually by almost 40%. Between 1990 and 1991 the use of diuretics decreased by around 23% and then on the number has been coming down to between 1% and 6% per year (AIHW 2001).
Antithrombotic and Antiplatelet drugs
Antithrombotic drugs have been greatly prescribes for preventing or treating blood clots. A marked increased in usage of antithrombotic agents have been recorded for the last decade. Between 1990 and 1998 usage levels have seen to quadruplicate with 2.0 DDD/1,000/day in 1990 compared with 9.3 DDD/1,000/day in 1998 (Mathur, 2002). Antiplatelet drugs, such as aspirin, ticlopidine and dipyridamole, are also used to prevent blood clots. Antiplatelet drug usage between 1990 and 1995 have been found to be relatively stable, however, the level showed a rise between 1995 and 1998 (Mathur, 2002).
Cholesterol and triglyceride lowering drugs
The use of cholesterol and triglyceride lowering drugs effective in preventing CHD in individuals with cardiovascular disease has substantially gone high. The usage increase has been eightfold between 1990 and 1998 with levels amounting to 5.3 DDD/1,000/day compared with 41.6 DDD/1,000/day respectively (Mathur, 2002).
The reduction in the incidence of heart attacks in Australia may be primarily attributed to reduced levels of one or more risk factors associated with coronary heart diseases. Improved medical care for those at higher risk of heart attack is another key reason to the number coming down steadily. Several studies indicate that the use of therapeutics for coronary heart ailments especially the use of lipid lowering and other effective drugs such as ACE inhibitors have substantially gone high and this has directly influenced the risk levels to regress, thus largely contributing to the down turn in heart attack rates in Australia over the past decades. McElduff et al. (2001) has pointed out that aggressive medical treatment of people with elevated risk factors and established CHD could reduce the number of coronary events by 40%. They also estimate that 14,000 coronary events could be avoided each year if the average level of cholesterol in the population was reduced by 0.5 mmol/L, smoking prevalence halved, prevalence of physical inactivity reduced to 25% and the use of
aspirin in people with established CHD was increased.
CHD risk factor levels such as tobacco smoking, high blood pressure, overweight and obesity, or physical inactivity needs to be suppressed. Currently, four people in ten have at least two of these risk factors (Stamler et al. 1999). Evidences also suggest high blood cholesterol, high blood pressure and cigarette smoking which account to 75% of the occurrence of CHD in the population (Magnus and Beaglehole 2001). Dobson et al. (1999) have observed decline in major coronary events in Australia between 1985 and 1993. This could be fully explained by reductions in risk factors and increased use of aspirin. Between 1991 and 1998 there was a 23% increase in the use of drugs for treating high blood pressure in Australia, which may have added to the observed decline in the incidence of high blood pressure among Australian adults. Lifestyle modification are essential for successful management of high blood pressure and this further lessen or get rid of the need for blood pressure lowering drugs (NHF 1999).
An overall projection to Australia health status associated with coronary heart disease drawn from the above studies would suggest that the decline in CHD mortality in Australia 1980 over to recent years can be explained by improvements in the management of CHD patients through risk factor reduction and improvements in treatment. However, some risk factors such as high cholesterol level, high blood pressure and obesity yet shows an upward trend, suggesting possibilities for increased CHD incidence and mortality rates in the future years. Nevertheless, rise in medical advancement and drug administration parallel shows an upward turn, suggesting that ailments can be kept under check. Similarly, associated risks due to lifestyle needs to be altered by modifying lifestyles to promote more physical activity and lowered intake of alcohol. This will further curb this ailment to a maximum in Australia. Therefore, this makes it clear that the exact status of CHD incidence and death rates in Australia is very much dependent on the present levels of high cholesterol level, high blood pressure and obesity in the population. Nevertheless, over time if increasing trend is to continue for drug administration then it is likely that CHD incidence and mortality rates will furthermore witness a downturn.
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