CHOLESTEROL

Cholesterol is a type of fat that circulates in the blood. It is essential for many metabolic processes, including the production of hormones and building cells. There are two main types of cholesterol: high density lipoprotein (HDL) and low density lipoprotein (LDL). HDL cholesterol is known as 'good' cholesterol, as it picks up excess cholesterol in the blood and takes it to the liver where it is broken down, helping to prevent blockages. Low levels of HDL may increase the risk of heart disease. LDL cholesterol, on the other hand, is known as 'bad' cholesterol, as high levels in the bloodstream can lead to fatty deposits developing in the arteries, increasing the risk of heart attack or stroke.^1,2

Data source and definitions Cholesterol levels are measured using a blood test. Abnormal cholesterol levels are defined as follows: Total cholesterol greater than or equal to 5.5 mmol/L LDL cholesterol greater than or equal to 3.5 mmol/L HDL cholesterol less than 1.0 mmol/L for men and less than 1.3 mmol/L for women In order to get an accurate reading for the LDL cholesterol, people were required to fast for 8 hours or more beforehand. The LDL cholesterol results presented here refer only to those people who did fast (approximately 78% of adults who participated in the National Aboriginal and Torres Strait Islander Health Measures Survey (NATSIHMS)).

TOTAL CHOLESTEROL

Total cholesterol is a measure of all the different types of fats in the blood. Abnormal or high total cholesterol is a major risk factor for coronary heart disease and stroke.³

In 2012–13, one in four Aboriginal and Torres Strait Islander adults (25.0%) had abnormal or high total cholesterol levels according to their blood test results. Yet only one in ten people (9.1%) from this group self-reported having high cholesterol as a current long-term health condition. This was similar to the rate found in the non-Indigenous population (10.1%). This suggests that the majority of Aboriginal and Torres Strait Islander people with high total cholesterol results were either unaware that they had the condition or did not consider it to be a long-term or current problem.



After adjusting for differences in age structure, Aboriginal and Torres Strait Islander people were less likely than non-Indigenous people to have high total cholesterol (rate ratio of 0.8). However, this is likely due to more Aboriginal and Torres Strait Islander people taking cholesterol-lowering medication, particularly after the age of 55 (see the Dyslipidaemia section of this publication).

Interestingly, there was no difference in the proportion of Aboriginal and Torres Strait Islander people with high total cholesterol between non-remote and remote areas in 2012–13. Rates were also similar for both men and women.

Similar to non-Indigenous Australians, the prevalence of high total cholesterol for Aboriginal and Torres Strait Islander people generally increased with age, peaking at 34.9% among those aged 45–54 years before dropping to 23.3% among those aged 55 years and over. However, this is likely the result of older people being more likely than younger people to take cholesterol-lowering medication.



Obesity, smoking and high blood pressure are all known risk factors for high cholesterol.⁴ The NATSIHMS showed that Aboriginal and Torres Strait Islander people who were obese were twice as likely to have high total cholesterol as those who were normal weight or underweight (30.3% compared with 16.3%). Likewise, around two in five people with very high or severe blood pressure (42.7%) had high total cholesterol compared with 23.3% of those with normal blood pressure levels.

Yet, surprisingly, cholesterol was not associated with smoking in 2012–13. In fact, rates of high total cholesterol for Aboriginal and Torres Strait Islander people who were current smokers (25.6%) were very similar to those for ex-smokers (25.9%) and people who had never smoked (23.6%). This was different to the pattern seen in the non-Indigenous population, where smokers were more likely to have high total cholesterol than non-smokers.⁵

The NATSIHMS also showed that Aboriginal and Torres Strait Islander people with high cholesterol were more likely to have other signs of cardiovascular disease. For example, around four in five people with high total cholesterol levels also had abnormal levels of LDL cholesterol (82.6%). People with high total cholesterol were also more than twice as likely as those with normal total cholesterol levels to have high triglycerides (45.7% compared with 17.6%).
LDL CHOLESTEROL

LDL cholesterol is a measure of 'bad' cholesterol in the blood. Over time, LDL cholesterol can build up in the blood vessels and arteries, blocking the passage of blood flow.⁶

Overall, the results for LDL cholesterol were very similar to those for total cholesterol. In 2012–13, 25.0% of Aboriginal and Torres Strait Islander adults had abnormal or high levels of LDL cholesterol. After accounting for age differences, Aboriginal and Torres Strait Islander people were less likely than non-Indigenous people to have high LDL cholesterol levels (rate ratio 0.8).

Similar to the age pattern observed for high total cholesterol, the prevalence of high LDL cholesterol increased with age until middle adulthood, before decreasing among those aged 55 years and over. Again, this could be due to older people being more likely than younger people to take cholesterol-lowering medication.



The associations between LDL cholesterol and health risk factors were also very similar to those for total cholesterol, with higher rates of LDL cholesterol among those who were overweight or obese, and those who had high blood pressure. Aboriginal and Torres Strait Islander people with abnormal LDL cholesterol were also more likely than those with normal LDL cholesterol to have high total cholesterol (84.9% compared with 3.8%) and high triglyceride levels (35.5% compared with 18.6%).
HDL CHOLESTEROL

HDL cholesterol, on the other hand, is the measure of 'good' cholesterol. HDL picks up excess cholesterol in the blood and takes it to the liver where it is broken down.⁶

In 2012–13, almost two in five Aboriginal and Torres Strait Islander adults (39.5%) had abnormal or low levels of HDL cholesterol, with higher rates among women (51.4%) than men (27.0%).

Unlike the other cholesterol biomarkers, abnormal HDL cholesterol was more common among Aboriginal and Torres Strait Islander people in remote areas than in non-remote areas (58.6% compared with 34.0%). Rates were especially high in very remote areas, where nearly two in three people (63.7%) had lower than normal levels of good cholesterol compared with one in three people (31.4%) in major cities.



After adjusting for age differences, Aboriginal and Torres Strait Islander people were nearly twice as likely as non-Indigenous people to have abnormal HDL cholesterol (rate ratio 1.8). For Aboriginal and Torres Strait Islander people, abnormal HDL cholesterol increased markedly during early adulthood, rising from 29.5% among those aged 18–24 years to 46.8% among those aged 35–44 years. This was noticeably different to the age pattern for non-Indigenous people, where rates remained fairly steady across all age groups (between 20.7% and 24.5%).

Low levels of HDL cholesterol were also associated with a range of lifestyle risk factors. For example, nearly half of those who were obese (49.1%) or who were current smokers (46.1%) had lower than normal levels of HDL cholesterol, compared with 29.3% who were normal weight or underweight and 35.0% who had never smoked.

Although people with low levels of HDL cholesterol were less likely to have abnormal total cholesterol (20.5% compared with 28.5%), they were more likely than those with normal levels of HDL cholesterol to have abnormal triglycerides (34.2% compared with 19.3%). Furthermore, people with low levels of HDL cholesterol were around twice as likely to have diabetes (18.2% compared with 7.0%) and chronic kidney disease (24.4% compared with 13.6%).

For more information on cholesterol, see Tables 1, 3, 4, 5, 6, 7, 8 and 17 on the Downloads page of this publication.


ENDNOTE

1 CSIRO, Cholesterol facts, <http://www.csiro.au/Outcomes/Health-and-Wellbeing/Prevention/CholesterolFacts.aspx>,
2 American Heart Association, 2014, Good vs. Bad Cholesterol, <http://www.heart.org/HEARTORG/Conditions/Cholesterol/AboutCholesterol/Good-vs-Bad-Cholesterol_UCM_305561_Article.jsp>,
3 Australian Institute of Health and Welfare, 2013, High blood cholesterol, <http://www.aihw.gov.au/high-blood-cholesterol/>,
4 Heart Foundation, Cardiovascular Condition, <http://www.heartfoundation.org.au/your-heart/cardiovascular-conditions/Pages/high-cholesterol.aspx>,
5 Australian Bureau of Statistics, 2013, 4364.0.55.005 - Australian Health Survey: Biomedical Results for Chronic Diseases, 2011—12, <https://www.abs.gov.au/ausstats/abs@.nsf/Latestproducts/4364.0.55.005Main%20Features12011-12?opendocument&tabname=Summary&prodno=4364.0.55.005&issue=2011-12&num=&view=>,
6 National Heart Foundation of Australia, 2013, Cholesterol, <http://www.heartfoundation.org.au/SiteCollectionDocuments/NAHU-Cholesterol.pdf>, Back to top