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FEATURE ARTICLE 2: DIABETES MELLITUS
In 2004-05, close to 700,000 people, or 3.5% of the population, reported they had diabetes (table 11.21). This was substantially higher than the 404,000 people, or 2.4% of the population, reporting it in 1995 (after age standardising the rate to adjust for age differences). This may reflect an increase in rates of diagnosis, rather than an increase in prevalence. Type 2 diabetes can go undiagnosed and an Australian study estimated that in 1999-2000, 7.5% of the population aged 25 years and over had diabetes mellitus, twice as many as had been diagnosed.
Type 2 is the most common type of diabetes. It is a degenerative condition in which the body tissue becomes resistant to insulin. In 2004-05, 83% of people with diabetes reported that they had this type. Type 2 most often develops in middle or older age and being overweight or physically inactive are important risk factors for this condition. Of those with type 2 in 2004-05, 81% had been aged 45 years or over when diagnosed. Most of the increase in the prevalence of diabetes since 1995 is due to an increase in type 2.
The less common type of diabetes is referred to as type 1 and is an autoimmune disease in which the body attacks and destroys the insulin producing cells. It has a relatively sudden onset and may arise in childhood, youth or later in life. At present there is no known way to reduce the risk of developing this disease. In 2004-05, 13% of people with diabetes reported they had type 1. The proportion of the population reporting type 1 remained the same over the period (0.5%) but there are some indications from other data sources of an increase in prevalence among children.
Some people have impaired glucose metabolism but not in the range that warrants a diagnosis of type 2 diabetes. These people are at higher risk of developing type 2 diabetes than other people, although lifestyle changes could often reduce this risk. An Australian study estimated that in 1999-2000, based on medical tests, 16% of the population aged 25 years and over (or 2 million people) had impaired glucose metabolism, mostly undiagnosed.
In 2004-05, the proportion of the population with diabetes increased with age from less than 0.5% of those aged under 25 years to 14% of those aged 65 years and over. A higher proportion of males than females had diabetes (4.0% compared with 3.2%), reflecting their higher rate of type 2 (3.4% compared with 2.6%). A similar proportion of males and females reported type 1 (0.5% compared with 0.4%).
There is interest in which population groups have higher rates of diabetes. In order to examine this variation, the following data are age standardised to adjust for differences in age structure between groups.
Health status often varies by socio-economic status. In 2004-05, people who lived in local areas rated as the most disadvantaged, based on characteristics such as income, employment and education, had higher rates of many long-term conditions, including diabetes (graph 11.22). The prevalence rate for diabetes was 2.3% in the least disadvantaged areas and increased to 5.4% in the most disadvantaged areas.
Prevalence also varied by birthplace. Diabetes was least prevalent among people born in north-west Europe (2.7%) and most prevalent among people born in southern and central Asia (8.7%). Such variation can reflect differences in the prevalence of risk factors, but ethnicity is also considered to be a risk factor for diabetes, independent of other factors.
In the NHS, overweight and obesity are assessed using Body Mass Index (BMI), calculated from self-reported height and weight. (End note 1)
Being overweight is a recognised risk factor for type 2 diabetes. People may lose weight for health reasons after being diagnosed with diabetes. Nevertheless in 2004-05, the proportion of people who had diabetes increased from 2.8% of people who were of normal weight to 14% of those who were obese, with a BMI score of 40 or more (graph 11.23). Between 1995 and 2004-05, it became more common to be overweight, with overweight or obese people increasing from 43% to 51% of the population aged 15 years and over. The obese category increased the most, from 12% to 17% (see the article Overweight and obesity in adults).
People with hypertension are more likely than others to develop type 2 diabetes. This may be because diabetes and hypertension share risk factors such as physical inactivity and overweight. In 2004-05, nearly half of the population with diabetes (46%) reported having been diagnosed with hypertension. Similar proportions of the whole population reported they had hypertension in 1995 (11%) and 2004-05 (10%).
Gestational diabetes is a temporary form of diabetes experienced by 3-8% of pregnant women, and women who have had this condition are at increased risk of later developing type 2. In 2004-05, 101,600 women (who had not subsequently developed another type of diabetes) reported that they had had gestational diabetes or currently had it.
Self-reported height and weight may also differ from measured height and weight. In 1995, a comparison of these two methods suggested that when self-reporting, people tend to overstate their height and understate their weight. For further details, see How Australians Measure Up, 1995 (4359.0).
Australian Institute of Health and Welfare, Australia's Health 2006, Cat. No. AUS 73, AIHW, Canberra
Council of Australian Governments, 14 July 2006 Communique, COAG, last viewed 10 October 2006, <http://www.coag.gov.au/meetings/140706/index.htm>
Department of Health and Ageing, Health Priorities, DoHA, last viewed 25 May 2006,
Dunstan D, Zimmet P, Welborn T, et al. 2001, 'Diabesity and Associated Disorders in Australia - 2000, the Accelerating Epidemic', The Australian Diabetes, Obesity and Lifestyle Study (AusDiab), International Diabetes Institute, Melbourne
Shaw JE and Chisolm DJ, 2003, 'Epidemiology and prevention of type 2 diabetes and the metabolic syndrome', Medical Journal of Australia, vol. 179, no. 7, pp 379-383
World Health Organisation, Diabetes: The cost of diabetes, WHO, last viewed 10 October 2006, <http://www.who.int/mediacentre/factsheets/ fs236/en>