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The Australian Diabetes, Obesity and Lifestyle Study
undiagnosed had retinopathy at the time of testing.
13
Around 10% of
Figure 3: Cardiovascular Disease Deaths According to
retinopathy among those with diagnosed diabetes was proliferative
Glucose Tolerance Status at Baseline
30
diabetic retinopathy. Albuminuria, present in 6% of the total Australian
population,
14
was also highly prevalent among those with diabetes
NGT 32.0% KDM 20.0%
(25.3%), as well as those with IFG and IGT (9.3 and 11.0%, respectively).
When considering multiple measures of kidney disease (proteinuria,
haematuria or reduced glomerular filtration rate), the prevalence of those
showing some signs of kidney damage in the total Australian population
was as high as 16%.
15
NDM 13.3%
Foot complications such as peripheral vascular disease and neuropathy
are a frequent manifestation of long-standing diabetes, and are the
main cause of non-traumatic lower-limb amputations. Both the IFG 13.3%
magnitude of these conditions and their management have been
IGT 21.3%
investigated using the AusDiab cohort, with around 13% of those with
diagnosed diabetes suffering from one or both of these conditions, and
only half of all those with previously diagnosed diabetes having had
their feet examined by a healthcare practitioner in the 12 months prior
* Prevalence in total Australian population:
Diabetes: 7.4%
to the survey, compared with almost 80% who reported having had
IFG/IGT: 16.4%
their eyes examined within the previous two years (Australian
guidelines recommend a minimum screening frequency of two years ratios (HRs) (95% confidence interval [CI]) for previously diagnosed
for retinopathy).
16,17
As the results of studies such as the UK Prospective diabetes and newly diagnosed diabetes were 2.3 (1.6–3.2) and 1.3
Diabetes Survey (PDS) and the Heart Protection Study (HPS) have (0.9–2.0), respectively. The risk of death was also increased in those with
demonstrated, tight control of glucose, lipids and blood pressure can IFG (HR 1.6, 1.0–2.4) and IGT (HR 1.5, 1.1–2.0). Demonstrating the link
significantly reduce the risk of diabetic complications.
18–21
However, between diabetes, CVD and death, 65% of all those who died of CVD
among people with diabetes in the AusDiab cohort, only half achieved had some form of glucose abnormality at baseline. After adjusting for
national targets
22–24
for each of these parameters, and only one in known CVD risk factors (including age and sex), previously diagnosed
seven people met all three targets. Achievement of the more stringent diabetes (HR 2.6, 1.4–4.7) and IFG (HR 2.5, 1.2–5.1) remained as
American Diabetes Association (ADA) targets
25–27
was naturally worse, independent predictors for CVD mortality; however, IGT did not (HR 1.2,
with only one in five achieving suggested lipid or blood pressure levels 0.7–2.2), perhaps reflecting the impact of treatment following diabetes
and only 2% meeting US targets for all three parameters.
28
diagnosis at baseline.
30
Incidence of Diabetes Key Challenges
The primary aim of the five-year follow-up of the AusDiab cohort was to
provide a unique examination of the natural history of diabetes and Recruitment and Response Rates
lesser states of abnormal glucose tolerance in a population-based One of the most challenging aspects of a project such as the AusDiab study
national sample. Therefore, one of the key findings from the follow-up is achieving an adequate response among the eligible population. Several
study was the incidence of diabetes, with 0.8% of the Australian adult features of the study make recruitment difficult, including the minimum two
population developing diabetes each year. This translates to 275 new and a half hours that participants are required to sacrifice in order to attend,
cases each day. As expected, most of these new cases came from the the requirement to fast for at least 10 hours, the small window of time (two
pre-diabetes categories of IFG and IGT (incidence of 2.5 and 3.5% per weeks) that the team is in a certain area and the absence of any financial
year, respectively, which was between 10- and 20-fold higher than that reward for participants. The response of around 55% to the baseline study
from normoglycaemia), providing further evidence of the burden that (this is the percentage of those who participated in a household interview
their high prevalence detected in the 1999–2000 survey will have on and then attended for physical testing) was seen by some as realistic given
diabetes rates in the future.
29
Obesity, hypertension, dyslipidaemia, the constraints of the study. However, others saw this as indicative of a
physical inactivity and metabolic syndrome all increased the risk of study that was national and population-based but not representative.
developing diabetes.
In an analysis of responders and non-responders to the study, responders
Mortality and Glycaemia were found to be slightly more educated (58.2 versus 51.3% with higher
The AusDiab cohort has been linked annually to the Australian National education), more likely to have been born in the UK (10.3 versus 8.8%),
Death Index (NDI) since 2004, providing a means of assessing the more likely to speak English at home (96.1 versus 93.6%) and more likely
mortality risk associated with the various states of glucose intolerance in to suspect they had diabetes (1.5 versus 0.5%). However, these
a national population-based sample. While the association between differences were small and unlikely to materially affect prevalence
diabetes and mortality is well established, less is known about the risk estimates. Of particular note was the higher percentage among
associated with IFG and IGT. After a median follow-up of 5.2 years, 298 responders who suspected they had diabetes. Of this group, fewer than
deaths had occurred in the AusDiab cohort (88 of these including 10% actually tested positive using an OGTT (compared with 4% who did
cardiovascular disease [CVD] as a cause of death). Compared with those not suspect diabetes), meaning that even this disparity would have made
with normal glucose tolerance, the adjusted all-cause mortality hazard little difference to the final diabetes prevalence estimates.
31
ASIA-PACIFIC CARDIOLOGY 27
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