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Biomedical risk factors are bodily states that contribute to the development of chronic disease. These states can be caused by a range of factors including: genetic, socioeconomic, psychological and behavioural, or a combination of these. Biomedical factors contribute to the risk of developing serious health conditions such as cardiovascular disease, type 2 diabetes and chronic kidney disease. Biomedical risk factors may also be influenced by behavioural risk factors—for example, physical inactivity and poor diet can adversely affect blood pressure and blood cholesterol. For more information on these in older Australians, see Behavioural risk factors.
Behavioural and biomedical risk factors tend to increase each other’s effects when they occur together in an individual [7]. Overall, older Australians experience a higher prevalence of biomedical risk factors than younger Australians, and these generally increase with age. This snapshot focuses on 3 biomedical risk factors that have direct and specific risks for health. These risk factors may be able to be modified by undertaking sufficient physical activity and eating a healthy diet.

High blood pressure

Blood pressure is the force that is exerted by the blood on the walls of the arteries (Box 1). When high blood pressure is controlled by medication, the risk of disease is reduced, although not to the levels seen in unaffected people [10].

Box 1: What is high blood pressure?

High blood pressure—also known as hypertension—is a major risk factor for cardiovascular diseases including stroke, coronary heart disease, heart failure, peripheral vascular disease and chronic kidney disease [8]. Blood pressure is measured by the level of systolic pressure (pressure in the arteries when the heart beats, pumping blood into the arteries) and diastolic pressure (pressure in the arteries when the heart is relaxed between beats), expressed as millimetres of mercury (mmHg). Blood pressure varies between individuals; as such, there are a number of different factors a medical practitioner will consider when diagnosing high blood pressure. The World Health Organization (WHO) defines blood pressure of 140/90 mmHg or more as high [10].

The methodology of determining the proportion of people with high blood pressure can differ between surveys. For example, while the Australian Bureau of Statistics (ABS) 2014–15 National Health Survey (NHS) uses data based on measured blood pressure, people who might otherwise have high blood pressure but are managing their condition with blood pressure medications are not included.

The proportion of adults with high blood pressure increases with age. Based on data from the ABS 2014–15 NHS, 1 in 2 people (47%) aged 75 and over had measured high blood pressure (42% for men and 51% for women) compared with 42% among people aged 65–74 (Figure 1).

Figure 1: Prevalence of high blood pressure in older people, by sex and age group, 2014–15

Column chart shows the prevalence of high blood pressure increases with age. It is more common among men than women for ages <74, and more common among women for ages 75+.

Source: ABS [1]

In Indigenous people blood pressure also increases with age, however, the prevelance of high blood pressure for Indigenous people is higher than for non-Indigenous people in younger age groups—based on the ABS 2011–13 Australian Aboriginal and Torres Strait Islander Health Survey, the greatest disparity between prevalence was for the 35–44 age group (1.6 times as high for Indigenous people). For Indigenous people aged 55 and over the proportion with high blood pressure (36%) was similar to that of non-Indigenous people (38%) [6].

Abnormal blood lipids (dyslipidaemia)

Blood lipids are fats in the blood and include cholesterol (a fatty substance that is an essential part of cell walls and is produced in the liver) and triglycerides (fat in the blood that assists in transporting and supplying metabolic energy throughout the body) [3]. Dyslipidaemia—abnormal levels of blood lipids—is a risk factor for chronic diseases such as coronary heart disease and for some types of stroke. Abnormal levels of blood lipids have previously been linked to atherosclerotic damage to arteries and heart disease [3].

The ABS 2011–12 Australian Health Survey (AHS) classifies a person as having dyslipidaemia if they had one or more of the following:

  • total cholesterol = 5.5 mmol/L
  • low density lipoprotein (LDL) cholesterol = 3.5 mmol/L
  • high density lipoprotein (HDL) cholesterol < 1.0 mmol/L for men, and < 1.3 mmol/L for women
  • triglycerides = 2.0 mmol/L
  • taking lipid-modifying medication [3].

In 2011–12, for both men and women, the prevalence of dyslipidaemia generally increases with age, peaking in the 65–74 age group (78% for men and 84% for women). Although the proportion was lower among those aged 75 and over (74% and 81%, respectively). The prevalence of specific types of dyslipidaemia varies:


1 in 3 people

1 in 3

People aged 65 and over (32%) in 2011–12 had a total cholesterol level that was considered high.


1 in 5 people

Over 1 in 5

People aged 65 and over (22%) had low levels of HDL (good) cholesterol in their blood.


3 in 10 people

3 in 10

People aged 65 and over (30%) had high levels of LDL (bad) cholesterol.


1 in 7 people

1 in 7

People aged 65 and over had high levels of triglycerides (some people have more than one type of dyslipidaemia) [2].


Impaired glucose regulation

Impaired glucose regulation is a characteristic of pre-diabetes, a condition in which blood glucose levels are higher than normal, although not high enough to be diagnosed with type 2 diabetes. There are two measures of impaired glucose regulation—impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) (Box 2). Both IGT and IFG are pre-diabetic states associated with insulin resistance—where cells fail to respond normally to insulin—which leads to high levels of blood sugar. Both of IGT and IFG are risk factors for type 2 diabetes, and are associated with a greater risk of heart disease. [7].

Box 2: How is impaired glucose regulation measured?

To test glucose tolerance, people fast for 8–12 hours and are given a glucose drink and their blood sugar levels are measured before and 2 hours after drinking.
People are diagnosed with IGT if they have blood glucose levels between 7.8 and 11.0 mmol/L 2 hours after the test (levels above this are classified as diabetes).

People are diagnosed with IFG if their blood glucose levels are between 6.1 mmol/L and 6.9 mmol/L after fasting (levels above this are classified as diabetes) [5].
The ABS 2011–12 AHS measured data on IFG, however, IGT was not measured and is not available for reporting in this snapshot.

For more information on diabetes in older Australians, see Diabetes.

Impaired fasting glucose

Based on data from the ABS 2011–12 AHS, IFG is more prevalent among older Australians, with 7% of people aged 65–74, and 8% of people aged 75 and over having the condition. Overall, 7% of older Australians had IFG. A further 13% had fasting blood glucose levels that classified them as having diabetes (IFG of 7.0mmol/L or above) [2].


References

  1. Australian Bureau of Statistics (ABS) 2016.National Health Survey: First Results, 2014–15. Canberra: ABS. Viewed 18 January 2017
    http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/4364.0.55.001~201415
    ~Main%20Features~Hypertension%20and%20measured%20high%20blood%20pressure~14
  2. ABS 2013. Australian Health Survey: Biomedical Results for Chronic Diseases, 2011–12. Canberra: AIHW. Viewed 05 January 2017 http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/4364.0.55.0052011-12
  3. Australian Institute of Health and Welfare (AIHW) 2016. Abnormal blood lipids. Risk factor prevalence. Canberra: AIHW. Viewed 31 October 2016 <http://www.aihw.gov.au/risk-factors/abnormal-blood-lipids/>
  4. AIHW 2016. High blood pressure. Risk factor prevalence—Table 7. Canberra: AIHW. Viewed 31 october 2016 http://www.aihw.gov.au/risk-factors/high-blood-pressure/
  5. AIHW 2016. Impaired fasting glucose. Risk factor prevalence. Canberra: AIHW. Viewed 31 October 2016 < http://www.aihw.gov.au/risk-factors/impaired-fasting-glucose/>
  6. AIHW 2015. Cardiovascular disease, diabetes and chronic kidney disease—Australian facts: Aboriginal and Torres Strait Islander people. Cardiovascular, diabetes and chronic kidney disease series no. 5. Cat. No. CDK 5. Canberra: AIHW.
  7. AIHW 2016. Australia’s health 2016. Australia’s health series no. 15. Cat. no. AUS 199. Canberra: AIHW.
  8. High Blood Pressure Research Council of Australia (HBPRCA) 2016. Frequently asked questions. Viewed 31 October 2016 http://www.hbprca.com.au/high-blood-pressure/faqs/
  9. Nathan D, Davidson M, DeFronzo R, Heine R, Henry R, Pratley R & Zinman B 2007. Impaired fasting glucose and impaired glucose tolerance. Diabetes Care Mar 30(3): 753–759
  10. World Health Organisation (WHO) 2003. WHO International Society of Hypertension (ISH) statement on management of hypertension. Journal of Hypertension 21:1983–1992