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After adjusting for differences in the age structure of the two populations, Indigenous men were 0.8 times as likely as non-Indigenous men to be overweight and 1.6 times as likely to be obese. The corresponding rate ratios for women were 0.9 and 2.2.
Indigenous and non-Indigenous comparisons
Reflecting the different age structures of the Indigenous and non-Indigenous populations, the median age of overweight/obese Indigenous men was 37 years, and for women, 38 years. The corresponding median ages for overweight/obese non-Indigenous men and women were 46 years and 48 years respectively.
In 2004-05, the proportions of overweight Indigenous and non-Indigenous women within each age group were not significantly different. A similar pattern was evident when comparing the proportions of overweight Indigenous and non-Indigenous men, apart from those aged 35-44 years. Indigenous men in this age group were significantly less likely than non-Indigenous men to be overweight (31% compared with 47%).
In 2004-05, the proportion of obese Indigenous women within each age group was significantly higher than the corresponding proportion of non-Indigenous women. A similar pattern was evident when comparing obesity rates for Indigenous and non-Indigenous men, apart from those aged 45-54 years. For Indigenous and non-Indigenous men in this age group, the difference in obesity rates was not statistically significant.
OVERWEIGHT/OBESITY AND OTHER SELECTED HEALTH RISK FACTORS
While excess weight increases the risk of developing certain chronic diseases, a person's health status may also be affected by the presence (and combination) of other risk factors. These may be behavioural (e.g. physical inactivity, smoking and risky/high risk alcohol consumption) or environmental (e.g. poor sanitation, limited access to fresh fruit and vegetables, overcrowded living conditions, barriers to accessing appropriate health services). This section presents information on behavioural risk factors and selected dietary factors in combination with overweight/obesity.
SELECTED BEHAVIOURAL RISK FACTORS
In 2003, the leading causes of the burden of disease among Indigenous men and women aged 35-54 years were high body mass and smoking, while for those aged 55 years and over, tobacco use, high body mass and physical inactivity were the major contributors (Vos et al 2007) (footnote 3). These findings are supported by results from the 2004-05 NATSIHS in which almost three-quarters of Indigenous adults in non-remote areas reported two or more of the following health risk factors: smoking, long-term risky/high risk alcohol consumption, physical inactivity and overweight/obesity. Overweight/obesity featured in the most common combinations of these four risk factors (ABS & AIHW 2008).
In the 2004-05 NATSIHS, overweight/obese Indigenous adults had lower smoking rates than those in the normal/healthy weight range. While some of these differences were not statistically significant, the differences in smoking rates for women in non-remote areas (45% compared with 58%) and men in remote areas (53% compared with 72%) were. In addition, overweight/obese Indigenous men in non-remote areas were significantly less likely than men of normal/healthy weight to have used illicit substances in the previous 12 months (18% compared with 37%).
These differences may, in part, be due to differences in the age profile of people in the normal/healthy and overweight/obese BMI categories. Just as rates of overweight/obesity are higher in older age groups, the prevalence of certain risk factors (e.g. smoking, alcohol consumption and illicit substance use) is higher in younger age groups. These associations should be taken into account when comparing the rates for risky behaviours among Indigenous adults who were overweight or obese with the corresponding rates for those in the normal/healthy weight range.
Among Indigenous adults who were overweight/obese in 2004-05, the prevalence of most other selected behavioural risk factors was similar for men and women. The exceptions to this were the rates of short-term and long-term risky/high risk alcohol consumption in non-remote areas. When compared with overweight/obese Indigenous women in non-remote areas, overweight/obese Indigenous men were significantly more likely to have also reported drinking alcohol at risky/high risk levels in the long-term (20% compared with 11%) and/or short-term (23% compared with 13%).
Indigenous and non-Indigenous comparisons
Overweight/obese Indigenous men and women reported higher rates of smoking and short term risky/high risk alcohol consumption than the corresponding rates for overweight/obese non-Indigenous men and women. After adjusting for differences in the age structure of the two populations, overweight/obese Indigenous women were twice as likely as overweight/obese non-Indigenous women to be a current smoker and were three times as likely to have drunk at risky/high risk levels in the short term. The corresponding Indigenous to non-Indigenous rate ratios for men were 1.8 and 1.6.
SELECTED DIETARY FACTORS
In the 2004-05 NATSIHS, Indigenous adults were asked a number of questions about food security and selected dietary behaviours (footnote 8). Results from the survey suggest that these health factors are more strongly influenced by, or associated with, geographic remoteness than they are with a person's body mass.
Indigenous adults who reported their height and weight in 2004-05 and who lived in remote areas:
When compared with Indigenous adults in the normal/healthy weight range, those who were overweight or obese were significantly more likely to drink low or reduced fat/skim milk (28% compared with 15% in non-remote areas; 8% compared with 4% in remote areas).
BMI AND SELF-ASSESSED HEALTH
In the 2004-05 NATSIHS, 41% of Indigenous adults assessed their health as excellent or very good, 36% assessed their health as good and 23% reported fair or poor health. Aboriginal and Torres Strait Islander people who were overweight or obese were less likely to report excellent/very good health and more likely to report fair/poor health than were people in the underweight or normal/healthy BMI categories. Overweight Indigenous adults were significantly more likely than those of normal weight to report fair/poor health (23% compared with 18%). There were also statistically significant differences between the proportions of overweight and obese adults reporting excellent/very good health (42% compared with 33%) and fair/poor health (23% compared with 29%).
BMI AND SELECTED LONG-TERM HEALTH CONDITIONS
This section presents associations between overweight/obesity and selected long-term health conditions. As is often the case with co-morbidities, the relationship between excess weight and long-term (chronic) health conditions is complex. Being overweight or obese can increase the likelihood of developing certain conditions, such as diabetes and heart disease, while the onset of these conditions may also restrict a person's capacity to control their weight through regular physical activity. For this reason, data have been presented on both the prevalence of selected long-term conditions among Indigenous adults who were overweight or obese, and BMI categories for adults with selected long-term conditions.
Of the 131,500 Indigenous adults who were overweight or obese in 2004-05:
When compared with Indigenous people in the normal/healthy weight range, overweight Indigenous adults were significantly more likely to have heart/circulatory problems (19% compared with 14%), arthritis (18% compared with 12%) and/or diabetes (13% compared with 5%). Similarly, the prevalence of heart/circulatory problems (29%), diabetes (17%) and asthma (20%) among obese Indigenous adults was significantly higher than among those who were overweight.
BMI(a) by prevalence of selected long-term health conditions, Indigenous persons aged 18 years and over(b) - 2004-05
BMI FOR SELECTED LONG-TERM CONDITIONS
Among Indigenous adults who reported their height and weight in 2004-05:
USE OF HEALTH SERVICES
Apart from consultations with doctors, Indigenous and non-Indigenous adults who were overweight/obese accessed most health services at similar rates to those in the normal/healthy weight range in 2004-05. However, in both populations the proportion of overweight/obese adults who had consulted a doctor in the previous two weeks was significantly higher than the corresponding rate for adults in the normal/healthy category (26% compared with 22% for Indigenous adults; 27% compared with 23% for non-Indigenous adults).
After adjusting for differences in the age structure of the two populations, overweight/obese Indigenous adults were:
While rates of service use are higher for overweight/obese Indigenous adults than for non-Indigenous adults in the same BMI category, this is consistent with the overall pattern of health service use between the two populations.
1. Body Mass Index (BMI) is calculated from reported height and weight information, using the formula: weight (kg) divided by the square of height (m). To produce a measure of the prevalence of overweight or obesity in adults, BMI values are grouped according to World Health Organization and National Health and Medical Research Council (NHMRC) guidelines. For example, the BMI for a person who weighs 100kg and is 1.7m tall would be 100 divided by 1.7 times 1.7 (2.89) = 34.6. In the 2004-05 NATSIHS and 2004-05 NHS, a person was categorised as 'overweight' if their BMI was in the range 25.0 to less than 30.0, and 'obese' if their BMI was 30.0 or greater. The person in this example would therefore be categorised as obese.
2. Age standardisation is a method used to remove the influence of age when comparing populations with different age structures. In order to make meaningful comparisons between Indigenous and non-Indigenous Australians, some data in this article have been age standardised to reflect the age composition of the estimated resident population of Australia as at 30 June, 2001. While age standardised rates do not show the prevalence of a particular characteristic, they can be used to derive a rate ratio which is a good indicator of the difference in prevalence. A rate ratio of 1.0 indicates parity, while Indigenous to non-Indigenous rate ratios greater than 1.0 indicate relative Indigenous advantage/disadvantage, depending on the indicator. For example, if the indicator is fair/poor self-assessed health and the Indigenous to non-Indigenous rate ratio is 1.5, this would indicate relative Indigenous disadvantage whereas the same rate ratio for excellent/very good self-assessed health would indicate relative Indigenous advantage.
3. The burden of disease and injury was assessed using Disability Adjusted Life Years (DALYS) - the sum of years of life lost due to premature death and years lived with disability. In 2003, the burden of disease and injury for the Indigenous population was estimated to be 95,976 DALYS, or 3.6% of the burden of disease for the total Australian population. For more information, see Vos et al 2007, The Burden of Disease and Injury in Aboriginal and Torres Strait Islander Peoples, 2003, School of Population Health, Brisbane.
4. According to the National Health and Medical research Council (NHMRC) guidelines, long-term risky/high risk alcohol consumption equates to 50ml or more of alcohol per day for males and 25ml or more of alcohol per day for females. In the 2004-05 NATSIHS, long-term alcohol risk levels were derived from the average daily consumption of alcohol in the seven days prior to interview.
5. Short-term alcohol risk levels in the 2004-05 NATSIHS were based on the frequency of consuming five (for females) or seven (for males) or more standard drinks at least once a week. One standard drink contains 12.5ml of alcohol.
6. Illicit substance use refers to the use of substances for non-medical purposes in the previous 12 months. Substances included under this definition in the 2004-05 NATSIHS included pain-killers or analgesics, tranquillisers or sleeping pills, amphetamines or speed, marijuana, hashish or cannabis resin, heroin, methadone, cocaine, hallucinogens, ecstasy or other designer drugs, petrol and other inhalants and kava.
7. The 2004-05 NATSIHS collected, from Indigenous people aged 15 years and over in non-remote areas, self-reported information about the frequency, intensity and duration of exercise undertaken in the two weeks prior to interview. From this information, an exercise score was derived, with scores then grouped into four categories. Physical inactivity in this snapshot comprises the 'Sedentary' and 'Low' exercise categories.
8. In the 2004-05 NATSIHS, food security was determined by asking adults whether or not they had run out of food in the previous 12 months and couldn't afford to buy more, and if so, whether they then went without food. Information on selected dietary behaviours comprised daily fruit and vegetable intake, type of milk usually consumed, and whether salt was added to food after cooking.
Australian Bureau of Statistics 2008, Overweight and obesity in adults 2004-05, ABS cat. no. 4719.0, ABS, Canberra.
Australian Bureau of Statistics and Australian Institute of Health and Welfare 2008, The Health and Welfare of Australia's Aboriginal and Torres Strait Islander Peoples, ABS cat. no. 4704.0, AIHW cat. no. IHW21, ABS & AIHW, Canberra.
Kondalsamy-Chennakesavan, S, Hoy, WE, Wang, Z, Briganti, E, Polkinghorne, K, Chadban, S, Shaw, J; AusDiab Study Group 2008, Anthropometric measurements of Australian Aboriginal adults living in remote areas: comparison with nationally representative findings, American Journal of Human Biology, May-Jun;20(3):317-24.
Piers, LS, Rowley KG, Soares, MJ, O'Dea, K 2003, Relation of adiposity and body fat distribution to body mass index in Australians of Aboriginal and European ancestry, European Journal of Clinical Nutrition, Aug;57(8):956-63.
Rutishauser, IH, McKay, H 1986, Anthropometric status and body composition in aboriginal women of the Kimberley region, Medical Journal of Australia, June 23;144 Suppl:S8-10.
Vos, T, Barker, B, Stanley, L, Lopez, A 2007, The Burden of Disease and Injury in Aboriginal and Torres Strait Islander Peoples, 2003, School of Population Health, Brisbane.
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