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Why are risk factors included in the National Health Priority Areas initiative?
The effect of risk factors on health depends not only on their prevalence in the population but also on the relative amount they contribute to the level of ill health in the population. Australia's most recent national study of the burden of illness and injury applied to 2003 and summarised the contribution of risk factors to the national burden for that year. Tobacco smoking was estimated to contribute the greatest burden (7.8% of the total health burden), followed by high blood pressure (7.6%) and overweight/obesity (7.5%). (Australia's health 2010 pages: 67-68, June 2010)
Most of the total burden of disease and injury in Australia in 2003 was attributed to chronic conditions, the leading contributors being cancers (19%) and cardiovascular diseases (18%). Determinants that contribute to the development of one or more chronic diseases include lifestyle behaviours such as tobacco smoking, physical inactivity, alcohol consumption, illicit drug use and unsafe sex; physiological conditions such as excess body weight, high blood pressure and high blood cholesterol; and social and environmental factors such as occupational exposures, intimate partner violence and air pollution. Some of these associations are presented in Table 3.1. (Australia's health 2010 pages: 67-68, June 2010)
Focus National Health Priority Area risk factors?
The initial focus, under the NHPA initiative, is on lifestyle and behavioural risk factors such as tobacco smoking, physical activity, and diet and nutrition. Emphasis is also placed on monitoring excess body weight, high blood pressure and high blood cholesterol.
Tobacco smoking
Risk factors contribute to over 30% of Australia's total burden of death, disease and disability. Tobacco smoking is the single most preventable cause of ill health and death in Australia. However, Australia's level of smoking continues to fall and is among the lowest for OECD countries, with a daily smoking rate of about 1 in 6 adults in 2007. (Australia's health 2010 pages: 61-63, June 2010)
Cigarettes and other tobacco products contain carcinogens (cancer-causing agents), nicotine (an addictive agent) and numerous other poisonous substances. People who use tobacco have an increased risk of developing coronary heart disease, stroke, heart failure, peripheral vascular disease, lung cancer, cervical cancer and osteoporosis. These risks increase with the number of cigarettes smoked daily, with the number of years of smoking, and especially when the habit is started at an early age.
Tobacco smoke affects not only the individual user, but also others who may be exposed to it. Environmental tobacco smoke has been shown to be associated particularly with the exacerbation of childhood respiratory diseases such as asthma.
Physical inactivity
Physical inactivity, defined as people undertaking 'insufficient' physical activity to achieve measurable health outcomes, is a strong risk factor for a range of NHPA diseases and conditions. It can also contribute to other risk factors such as increases in blood pressure, blood cholesterol levels and overweight and obesity.
There is strong evidence that a lack of regular physical activity is associated with an increased risk of mortality and morbidity from heart and vascular diseases, particularly coronary heart disease. There is also some association between physical inactivity and an increase in risk of some types of stroke, heart failure and peripheral vascular disease. Insufficient physical activity increases the risk of Type 2 diabetes, osteoarthritis, osteoporosis and some cancers; in particularly, an increased risk for post-menopausal breast cancer and colorectal cancer.
Physical activity has a beneficial effect on improving various aspects of health including cardiovascular disease, musculoskeletal health and diabetes. Physical activity may also assist in the reduction in symptoms of depression and reduce the risks of developing some cancers, such as prostate cancer.
Physical inactivity has been ranked second only to tobacco smoking, in terms of the burden of disease and injury from risk factors in Australia.
Poor diet and nutrition
Diet and nutrition play a major role in health and disease. In recent decades much evidence has shown that dietary patterns can contribute to the risk of various diseases and their immediate risk factors.
Poor diets often result from over-consumption of food in general, or diets high in energy-rich components such as fat. A poor diet may also be low in dietary fibres or complex carbohydrates, and deficient in certain vitamins and minerals.
In developed nations, the problem is more closely associated with excess consumption rather than nutritional deficits that are experienced in developing nations.
Poor diet plays a key role in the development and progression of NHPA diseases such as coronary heart disease, stroke, Type 2 diabetes and some forms of cancer such as colorectal cancer and post-menopausal breast cancer. It may also increase the risk of prostate cancer, although this link is less clear. Poor diet and nutrition also contributes to a variety of other health risk factors such as high blood pressure, excess weight and high blood cholesterol.
Excess body weight
Excess body weight, a term used to refer to both overweight and obesity, is a condition that occurs due to excess body fat resulting from an energy imbalance, where energy consumption (nutritional patterns) exceeds energy expenditure over a considerable period of time.
Excess body weight has been clearly linked with increased risk of mortality and morbidity from heart and vascular diseases, such as coronary heart disease, stroke, heart failure and peripheral vascular disease. There is also substantial evidence for a causal relationship between excess body weight and increased risk for a number of NHPA diseases such as Type 2 diabetes, gestational diabetes and some cancers such as colorectal cancer, prostate cancer and post-menopausal breast cancer.
Excess body weight is also associated with a range of other NHPA risk factors, such as high blood pressure, impaired glucose tolerance and high blood cholesterol. The risk of developing more than one NHPA disease or condition also increases with increasing levels of excess weight. Overweight was estimated to account for 4.3% of the total burden of disease in Australia in 1996.
High blood pressure
High blood pressure (hypertension) is a condition that is defined by the WHO as when either the systolic blood pressure is 140 mmHg or more; or diastolic blood pressure is 90 mmHg or more. The term 'blood pressure' refers to the forces exerted by blood on the walls of the arteries and is measured as systolic pressure over diastolic pressure. Systolic blood pressure reflects the maximum pressure in the arteries when the heart muscle contracts to pump blood. Diastolic blood pressure reflects the minimum pressure in the arteries when the heart muscle relaxes.
High blood pressure is a major risk factor for a range of cardiovascular diseases. The risk of disease increases as the level of blood pressure increases. It can be controlled via changes in nutrition, weight, physical activity and medication. The burden of disease in Australia that can be attributed to high blood pressure was estimated to be more than 5% of the total burden in DALY terms among Australians in 1996.
Increased risk to two major forms of cardiovascular disease, coronary heart disease and stroke, as well as other serious complications are directly associated with high blood pressure. It can increase the risk of these two cardiovascular diseases by two to four times. High blood pressure is also associated with an increased risk of heart failure and peripheral vascular disease.
High blood cholesterol
High blood cholesterol (hypercholesterolemia) means there is too much cholesterol (a fat-like substance) in the blood. This leads to the build up of cholesterol, on the walls of the arteries of the heart and other parts of the body, in a process called atherosclerosis, resulting in the arteries becoming clogged and having decreased or inhibited blood flow.
High blood cholesterol is a major risk factor for coronary heart disease, the single greatest cause of death and disability in Australia. It is also associated with an increased risk of ischaemic stroke, heart failure and peripheral vascular disease. For most people, a diet high in saturated fat is the main factor that raises blood cholesterol levels. High blood cholesterol accounted for almost 3% of the total burden of disease of Australians in 1996.
The set of indicators for risk factors covers the major underlying risk factors which commonly contribute to the NHPA diseases and conditions. This includes tobacco smoking, insufficient physical activity, excess body weight, high blood pressure, high blood cholesterol and diet and nutrition.