Chronic disease risk factors

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A number of risk factors contribute to the onset, maintenance and prognosis of many of the chronic diseases included on this web area. These are shown in the figure below as 'behavioural risk factors', 'biomedical risk factors' and 'other factors'.

Figure: Behavioural risk factors, biomedical risk factors and other factors

Source: Australian Institute of Health and Welfare (AIHW) 2002. Chronic diseases and associated risk factors in Australia, 2001. Canberra: AIHW.

This page focuses on the behavioural and biomedical risk factors that are avoidable or modifiable and where there is potential for health gain through their early prevention or appropriate management. For a brief discussion of the 'other factors', click here.

Risk factors often coexist or interact with one another. Most of the chronic diseases have multiple risk factors. The web of relationships between these risk factors and chronic diseases covered here is shown in the table below.

**Table: Relationships between various chronic diseases, conditions and risk factors**
Disease	Risk factor
	Behavioural				Biomedical
	Poor diet	Physical inactivity	Tobacco	Alcohol misuse	Excess weight	High blood pressure	High blood cholesterol
Coronary heart disease
Stroke
Lung cancer
Colorectal cancer
Depression
Diabetes
Asthma
Chronic obstructive pulmonary disease
Chronic kidney disease
Oral diseases
Osteoarthritis
Osteoporosis
Condition
Excess weight
High blood pressure
High blood cholesterol

Source: Australian Institute of Health and Welfare (AIHW) 2002. Chronic diseases and associated risk factors in Australia, 2001. Canberra: AIHW.

While most of these risk factors are considered to be 'adult' behaviours and conditions, the situations that lead to their initiation often begin early in life, or even in the womb. Thus it is important to have a life course perspective of chronic diseases and their risk factors, which recognises the interactive and cumulative impact of social and biological influences throughout life.

For more information on the risk factors click the links in the Table above.

Poor diet and nutrition

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The foods we eat provide nutrients needed to maintain our health, including carbohydrates, protein, healthy forms of fat, dietary fibre, vitamins, and minerals. A healthy diet provides adequate amounts of nutrition required to nourish our bodies while avoiding harmful excesses of some nutrients. The National Health and Medical Research Council recommends a diet that is high in fruits and vegetables, with sufficient amounts of iron, calcium and fibre, but is low in fat, salt and sugar.

A poor diet can contribute to chronic diseases directly or indirectly through a range of biomedical risk factors such as high blood cholesterol and high blood pressure. It typically includes over-consumption of food in general, or diets high in energy-rich components such as fat. It may also be low in dietary fibres or complex carbohydrates, and/or deficient in certain vitamins and minerals. This can play a key role in the development and progression of chronic diseases such as:

Some examples of the biomedical risk factors through which poor diet can lead to chronic diseases are:

high blood cholesterol levels due to high intake of saturated fat
overweight and obesity due to a high intake of energy-rich foods (including carbohydrates and fat), especially if physical activity levels are low
high blood pressure due to a high intake of salt.

On the other hand, a high intake of plant foods (such as cereals, fruit, vegetable and legumes) may help to protect against coronary heart disease, some cancers and excess weight. There is good evidence that regular consumption of fish, particularly oily fish, reduces the risk of coronary heart disease.

A healthy diet can be achieved through the consumption of

a wide variety of foods including plenty of cereals, vegetables and fruit
adequate amounts of water and other fluids
foods high in iron (e.g. lean meats) and calcium (e.g. dairy foods),

and limiting the intake of

added sugars, salt and alcohol
fats, particularly saturated fat.

One way to measure poor diet and nutrition in the population is to compare dietary intake with recommended levels. Based on the 1995 ABS National Nutrition Survey, 2 in 3 Australians were not consuming the National Health and Medical Research Council's recommended level of vegetables, 4 in 5 were not consuming enough fruit, and 1 in 2 males and 1 in 3 females were not eating recommended levels of cereal foods.

Additional information on Australian diet and nutrition levels and trends can be found in the Statistics section of this website.

Physical inactivity

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Physical activity is an important factor in maintaining good health. Low or insufficient levels of physical activity (physical inactivity), as defined in Box 1, increase the risk for developing chronic diseases such as:

It also contributes to

high blood pressure
excess weight
high blood cholesterol.

By contrast, regular physical activity can reduce the risk of many of these chronic diseases and help improve the levels of blood pressure, blood cholesterol and body weight. Another positive health outcome is protection against injury, specifically falls. Physical activity has also been associated with a reduction in risk for poor mental health, mainly through a reduction in the severity of depressive symptoms and anxiety.

**Box 1: Definitions of physical activity levels**
For statistical purposes, physical activity is defined as either 'sufficient' for health benefits or 'insufficient'. 'Sufficient' activity is at least 150 minutes of moderate-intensity physical activity accrued over at least five sessions per week. Examples of moderate - intensity activity are brisk walking, swimming, doubles tennis and medium-paced cycling. 'Insufficient' activity is either no participation in physical activity or physical activity that is less than the amount required to meet the 'sufficient' category. Source: Armstrong T, Bauman A & Davies J 2000. Physical activity pattern of Australian adults. Results of the 1999 National Physical Activity Survey. Canberra: AIHW.

Data from the 2000 National Physical Activity Survey show that about 54% of Australians aged 18-75 years were not undertaking leisure-time physical activity at the levels recommended to obtain a health benefit, including 15% who reported no physical activity at all.

Additional information on levels and trends of physical activity in Australia can be found in the Statistics section of this website, and in the AIHW risk factor data store.

Tobacco

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The use of tobacco, most often in the form of cigarette smoking, is a widespread behaviour with serious health consequences. Cigarettes and other tobacco products contain carcinogens (cancer-causing agents), nicotine (an addictive agent) and numerous other poisonous substances. Tobacco smoke affects not only the individual user, but also others who may be exposed to it. Smoking during pregnancy carries risks of complications for the child and mother. Tobacco smoking contributes to many chronic diseases including:

The risks increase with the number of cigarettes smoked and with the number of years smoking, especially when tobacco smoking is started at an early age. Results from the 2001 National Drug Strategy Household Survey show that just under 20% of Australians aged 14 years and over smoked daily, with 21% of males and 18% of females being daily smokers. Among teenagers, however, girls (16%) are more likely to be daily smokers than boys (14%).

Additional information on smoking levels and trends in Australia can be found in the Statistics section of this website, and in the AIHW risk factor data store.

Alcohol misuse

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Although most people drink moderately and without ill-effect, over-consumption of alcohol in the long term contributes to several chronic physical, psychological and behavioural health problems, including:

Alcohol misuse is associated with increased risk of stroke and coronary heart disease through its contribution to high blood pressure.

Furthermore, high risk consumption of alcohol is frequently found together with tobacco smoking, and the two combined are strongly associated with oral, throat and oesophageal cancer.

Low to moderate levels of alcohol consumption can protect against high blood pressure, coronary heart disease and stroke. However, alcohol use for some individuals even at level usually regarded as moderate, increases the risk of a range of diseases and injuries.

The current classifications for levels of alcohol use in Australia are shown in the box 2 below:

**Box 2: Risk of alcohol-related harm in the long term (standard drinks)**
High risk alcohol consumption: Males = 7 or more standard drinks/day Female = more than 5 or more standard drinks/day Risky alcohol consumption: Males = 5 to 6 standard drinks/day Female = 3 to 4 standard drinks/day Low risk alcohol consumption: Males = up to 4 standard drinks/day Females = up to 2 standard drinks/day Note: A standard drink = 10g alcohol. Source: National Health and Medical Research Council 2001. Australian alcohol guidelines: health risks and benefits.

Results from the 2001 National Drug Strategy Household Survey show that 10% of Australians aged 14 years and over drink at levels considered to be harmful for long-term health - 7% at 'risky' levels and 3% at 'high risk' levels.

Additional information on levels of alcohol misuse in Australia can be found in the Statistics section of this website, and in the AIHW risk factor data store.

High blood pressure

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High blood pressure (hypertension) is one of the most prevalent and chronic health risk factors in Australia. When combined with other diseases and conditions such as diabetes and high blood cholesterol, the health risk associated with high blood pressure is significantly increased.

The term 'blood pressure' refers to the forces exerted by circulating blood on the walls of the arteries, with two recordings, systolic and diastolic. Systolic pressure is the peak blood pressure measured as the heart muscle contracts to pump blood from its main chamber, and diastolic pressure is the minimum blood pressure as the heart muscle relaxes to take more blood into its chambers. Although 'high' blood pressure is usually defined as being above a particular level, there is no threshold level of risk, and as pressure increases so does the risk of certain diseases.

According to the World Health Organisation, high blood pressure is defined as:

systolic blood pressure greater than or equal to 140 mmHg, or
diastolic blood pressure greater than or equal to 90 mmHg, or
receiving medication for high blood pressure.

This definition is also used in Australian surveys.

High blood pressure is a major risk factor for the following chronic diseases:

There are a number of mechanisms by which high blood pressure affects the vascular system. If the pressure in the blood vessels is too high, the heart is force to pump harder to push blood through the body; over time this force can overtax the heart and lead to heart failure. High blood pressure in the vessel walls also contribute to atherosclerosis (the abnormal build-up of substances on the inner walls of the arteries) and therefore to its complications, such as angina and heart attack. High blood pressure can also be both the cause and result of kidney disease.

A variety of factors contribute to the development of high blood pressure:

excess weight
excess alcohol consumption
physical inactivity
poor diet and nutrition, particularly high salt intake.

In Australia and similar countries, the level of blood pressure tends to increase with age, so that as people get older, they are more at risk of developing high blood pressure.

The 1999-2000 Australian Diabetes, Obesity and Lifestyle Study estimated that approximately 3.7 million (30%) Australians aged 25 years and over had high blood pressure or were taking medication for the condition. However, the proportion of Australians with high blood pressure has declined over the past 20 years.

Addition information on levels and trends in high blood pressure can be found in the Statistics section of this website, and in the AIHW risk factor data store.

The National Health and Medical Research Council recommends a number of lifestyle changes that can reduce high blood pressure, including:

reducing excess weight
participating in at least 30 minutes of moderate-intensity physical activity every day
limiting alcohol intake to two or less standard drinks per day
reducing salt in the diet.

A variety of drug treatments is also available to manage the condition if lifestyle measures appear insufficient.

Regular monitoring of blood pressure levels is important, since there are no symptoms associated with increased levels of blood pressure.

High blood cholesterol

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A high level of blood cholesterol (hypercholesterolemia) is a major risk factor for coronary heart disease, the single greatest cause of death and disability in Australia. It also increases the risk of ischaemic stroke.

Cholesterol is a fatty substance produced by the liver and carried by the blood to supply the rest of the body. It has several functions essential to life, including its use as part of cell walls and in producing steroid hormones. However, when the level of cholesterol in the blood becomes high, this can be a prime factor in the development of atherosclerosis, the process that blocks arteries through abnormal build-ups of substances on their inner walls.

For adults, a total blood cholesterol level of 5.5 mmol/L or higher is described as 'high', but this is an arbitrary cut-point and heart disease risk increases continuously from quite low cholesterol levels.

The 1999-2000 Australian Diabetes, Obesity and Lifestyle Study estimated that over six million Australian adults aged 25 years and over (50%) had blood cholesterol levels higher than 5.5 mmol/L.

Additional information on levels and trends in high blood cholesterol can be found in the Statistics section of this website, and in the AIHW risk factor data store.

For most people, the most important contributor to high blood cholesterol is a diet high in saturated fats, which are found most commonly in meat and dairy products and in many takeaway and processed foods. Monounsaturated and polyunsaturated fats (from vegetable oils, nuts, seeds, and fish) do not increase blood cholesterol levels, and in some cases may low them.

Genetic factors also affect blood cholesterol levels and some people have a genetic predisposition to high cholesterol.

High blood cholesterol is mostly preventable by lifestyle changes including lowered intake of saturated fat, reduction of excess body weight and increased physical activity.

Drug therapies have also shown to be beneficial in lowering blood cholesterol levels if lifestyle measures appear insufficient.

Regular monitoring of blood cholesterol levels is important, since there rarely are visible symptoms associated with increased levels of cholesterol.

Excess weight

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It is normal and healthy for people to carry some fat on their bodies, but when this fat is excessive, this is referred to as a condition of overweight or excess weight. Those who are very overweight are described as obese. Excess weight arises through an energy imbalance over a substantial period, where the dietary energy intake exceeds the energy expended through physical activity.

Excess body weight is associated with a variety of chronic diseases including:

Excessive body weight is also associated with high blood pressure and high blood cholesterol: with increasing levels of excess weight, the risk of both high blood pressure and high blood cholesterol is increased.

The measurement of excess weight as a risk factor for chronic diseases is not simple as both overall fat and regional distribution of fat contribute to chronic disease development and progression. Two proxy measures for excess weight are body mass index (BMI) and waist circumference.

BMI is the ratio of weight (in kilograms) divided by height (in metres) squared. The weight classifications and their ranges are shown in Box 3.

**Box 3: Classification of weight status by BMI and waist circumference**
Body mass index (kg/m²⁾Underweight less than 18.5 Normal weight 18.5 and less than 25 Overweight (but not obese) 25 and above, but less than 30 Obese 30 and above Waist circumference (cm) Males: Normal less than 94 Overweight 94 to less than 102 Obese 102 and above Female: Normal less than 80 Overweight 80 to less than 88 Obese 88 and above Source: AIHW National Health Data Dictionary.

The 1999-2000 Australian Diabetes, Obesity and Lifestyle Study indicates that over 7.4 million Australians aged 25 years and over (60%) had a BMI score of 25 or higher, and thus had excess weight. Of these, 2.6 (21%) had a BMI score of 30 or higher, and thus were obese. Further information on BMI scores in Australia can be found in the Statistics section of this website, and in the AIHW risk factor data store.

Waist circumference acts as a guide to fat located in the abdominal region (central or abdominal obesity). According to the classifications in Box 3, in 1999-2000 more than a quarter of Australian males aged 25 years and over (27%) and a third of females (34%) could be classified as abdominally obese. A further 29% of males and 23% females were abdominally overweight.

Although a widespread and increasing phenomenon, excess weight for most people is not inevitable. In principle there is scope to reduce the problem by modifying dietary intake and fostering greater physical activity. However, this would require changes in personal lifestyles.

Chronic disease risk factors

Recent releases

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Poor diet and nutrition

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Physical inactivity

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Tobacco

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Alcohol misuse

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High blood pressure

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High blood cholesterol

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Excess weight

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