The true rates may be much higher than current Australian data suggests – especially for type 2 diabetes.
Rates of diabetes in Australia, especially type 2, are substantially higher than estimated thanks to under-enrolment in the national registry.
A team led by Emma Cox from the School of Public Health at Sydney University developed an algorithm to more accurately assess the burden of diabetes in NSW by using linked administrative data.
They started with the Sax Institute’s 45 and Up Study, which includes a cohort of almost 270,000 adults aged 45 and over who provided data that could be linked to external records – the PBS (claims for dispensed insulin and glucose-lowering medicines), Medicare (diabetes-specific Medicare claims), NSW Admitted Patient Data Collection (diabetes-related hospital admissions) and the National Diabetes Services Scheme, the national registry.
The resulting algorithm classed members of the cohort as having certain, uncertain or no diabetes.
Of the 53,700 individuals with diabetes identified by the algorithm, less than 35,000 were registered to the NDSS – only about 65%.
“The NDSS currently estimates 1.3 million Australians aged 45 + years to be living with diabetes,” the authors wrote.
“If the levels of non-registration with the NDSS observed in our study population were reflected at a national level, we estimate the number of individuals with diabetes may be closer to two million amongst people aged 45 + years.”
Dr Gideon Meyerowitz-Katz, a research fellow at University of Wollongong who works as a chronic disease epidemiologist and wrote his PhD on diabetes epidemiology, and who was not involved in the study, said he was only surprised that the underdiagnosis wasn’t greater.
“We have known for some time that NDSS estimates are likely to be too low, because they rely on people taking positive action and enrolling in the scheme,” he told TMR.
“There are many reasons that people might find that hard, resulting in quite a lot of people who don’t sign up. This paper has a strong methodology and gives us a reasonable estimate of the rate of underestimation in diabetes rates, although it may not apply to states outside of NSW.”
Professor Grant Brinkworth, director of research at Diabetes Australia, said understanding the true scale was “essential if we want to improve outcomes for individuals and manage the national impact of this condition”.
“If people aren’t visible in the data, they’re also invisible to policy and funding decisions,” he said.
The NDSS did not respond to questions.
