Diabetes single map Consumer summary (169kb, PDF)

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The goal of this Atlas of Healthcare Variation domain is to investigate the quality of care provided to people with diabetes. These data are not intended for judgement or definitive statements of quality, rather they are intended to raise questions about potential areas for quality improvement. The indicators were developed with the assistance of an expert advisory group. 

2016 revision

In 2016, the Ministry of Health worked with a range of experts to update and improve the VDR algorithm to more accurately estimate diabetes prevalence. The revised VDR algorithm, based on a comparison with diagnostic laboratory data, is believed to have a specificity of around 97% and sensitivity of around 87%. The revised VDR gives estimates around 10% lower than the old version, and figures based on this should no longer be used.

In order to keep a consistent time series, historical versions of the VDR have thus been re-extracted using the updated algorithm. For further information, or if you want updated VDR data please contact data-enquiries@moh.govt.nz.

Update to include 2016 data

(Updated November 2017)

This Atlas has been updated using data from the updated VDR for 2014–16.

Key messages

  • The new algorithm estimates 236,000 people had diabetes in 2015 and 241,000 in 2016.The previous VDR estimated 260,050 people with diabetes in 2015 – see above for further detail. 
  • In 2015, diabetes prevalence varied more than two-fold by DHB, from between 10 to 27 percent of a DHB population aged 65–74.
  • The regular use of medicines for glycaemic control (insulin or metformin) varied 1.8-fold by DHB, from 34 to 61 percent of those with diabetes regularly receiving insulin or metformin.
  • The proportion of bed-days occupied by people with diabetes for any reason increased in 2015. This varied four-fold between DHBs. The percent of bed-days occupied by people with diabetes aged 65–74 ranged from 10 to 40 percent.

Key findings

Diabetes prevalence is increasing faster in some DHBs than others

The prevalence of diabetes increased significantly with age, from a mean of 0.33 percent in those aged 0–24 years to 18 percent in people aged 75 years and older.

This is a slight reduction from rates previously reported, reflecting changes to the VDR algorithm and resulting in a reduction from 5.7 percent estimated to have diabetes to 5.2 percent.

Pacific peoples had a significantly higher prevalence of diabetes than all other ethnic groups, while those identifying as European/Other had significantly lower rates of diabetes. People of Indian ethnicity are not presented separately here; however, rates of diabetes in Indian populations are similar to those observed in Pacific peoples.

Diabetes Table1 Dec17

Good glycaemic control is important for outcomes

If HbA1c does not meet an agreed target with dietary and lifestyle changes, drug therapy is recommended. Insulin and metformin are well proven. Evidence suggests good glycaemic control benefits microvascular outcomes.  The provision of comprehensive cardiovascular risk management for people with diabetes (such as blood pressures and lipid management) has largely been shown to improve macro-vascular outcomes. 

Insulin and metformin use varied

Given both the lack of data on clinical condition and the inability to split by the type of diabetes, these indicators of medication use are not intended to suggest an ‘ideal’ rate of use, rather they provide a high level view. Wide variation may raise questions such as do DHBs with lower than average rates of medication use have lower or higher rates of diabetes complications?

Nationally, 61 percent of people with diabetes aged 25 years and over regularly received either insulin or metformin, with use highest in those aged 65–74. This varied 1.8-fold by DHB, ranging from 34 to 61 percent.

Metformin is the standard initial drug treatment for type 2 diabetes. Use increased with age. On average,28 percent of people with diabetes aged 25–44 regularly received metformin compared with 57 percent of those aged 65–74.

On average, 22 percent of people with diabetes regularly received insulin. People of Asian ethnicity received significantly less insulin than people of all other ethnic groups. As might be expected, insulin use was highest in the 0–24-year age group with diabetes, with 62 percent of these regularly dispensed insulin.

Intensive management of high blood pressure and microalbuminuria

On average, 48 percent of people with diabetes received angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blockers (ARB) medicines. Use increased significantly with age up to 74 years. There was limited variation between DHBs. Intensive management of blood pressure and microalbuminuria is recommended to prevent progression of renal disease in diabetes. ACEI and ARB are first-line treatments for raised blood pressure and/or microalbuminuria.

The impact of diabetes on life expectancy is magnified by a younger age at diagnosis, highlighting the importance of glycaemic control, blood pressure management and prevention of kidney disease in younger people with diabetes.

Table Two shows that Māori and Pacific people have a higher rate of ACEI or ARB use at a younger age however there are data to showing Māori and Pacific people have significantly higher rates of end-stage renal disease. A recent publication found Māori and Pacific people have a relative risk of 6.48 for developing end stage renal disease due to type 2 diabetes when compared to other New Zealanders. [1]

Diabetes Table2 Dec17

Complications – admissions for diabetic ketoacidosis and hypoglycaemia varied by age

Note data from 2011 is presented for these indicators as they were not affected by the update to the VDR.

Nationally, the rate of admissions to hospital for diabetic ketoacidosis were at least ten-fold higher in those aged 0–24 years. Whilst the count of admissions for hypoglycaemia were highest in those aged 65 years and over, the rate was highest in the youngest age group. The numbers in each age group were too low to report by DHB. 

Diabetes Table3 Dec17

Complications – lower limb amputations increase with age

Lower limb amputation rates increased significantly with age, with 96 percent of amputations occurring in those aged 45 years and over. This rare complication affected only 0.19 percent of the diabetes population in a year. 

People with diabetes occupied more bed-days for any reason (2013–15 data)

The number of medical and surgical bed-days occupied by people with diabetes was compared with the total occupied medical and surgical bed-days. On average, people with diabetes occupied 17.9 percent of total bed-days, despite a population prevalence of diabetes of 5.2 percent. In 2016, age-specific rates varied over two-fold.

Age had a significant effect on occupied bed-days. People with diabetes aged 45–64 years occupied 22 percent of total bed-days, compared with a population prevalence of 8.2 percent of people with diabetes in this age group.

People of Māori, Pacific peoples and Asian ethnicities with diabetes occupied significantly more bed-days than those in the European/Other ethnic group – 26 percent on average compared with 15.2 percent.

Regular laboratory testing was lowest for screening renal disease (ACR)

People with diabetes who received one or more laboratory tests in a year for haemoglobin A1c (HbA1c), albumin: creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR) was analysed. On average, 87 percent received an HbA1c test, 66 percent an ACR test and 84 percent an eGFR test.

Rates differed by ethnicity. Pacific peoples and Asian ethnic groups had higher rates of testing than those of Māori and European/Other ethnicities.

Diabetes Table4 Dec17 

Questions raised

  • How many of these results can be explained by the predominant type of diabetes?
  • Are rates for specific indicators lower or higher than might be expected?
  • Is there room for improvement in any of these indicators?
  • Do results reflect local differences in care?

Method and data source

This domain draws on data contained in the Virtual Diabetes Registry, which was developed by the Ministry of Health to track the number of people diagnosed with diabetes. The registry combines and filters various sources of health information, including the National Minimum Dataset, the National Non-admitted Patients Collection (outpatients), the Pharmaceutical Collection, the Laboratory Claims Collection and the Primary Health Organisation Enrolment Collection. The registry was used to estimate the incidence of diabetes. These data are based on an algorithm so should be interpreted with some caution. The Atlas does not use any patient-identifiable data. 

Limitations

The Pharmaceutical Collection contains claim and payment information from community pharmacists for subsidised dispensing. This collection does not indicate whether a medicine was taken or whether the dose was effective. Over-the-counter medicines are not included.

In selecting indicators for oral hypoglycaemic medication use, the group decided to focus only on metformin, as the first line agent for people with type 2 diabetes and insulin as the key medication for people with type 1 diabetes. There is no ideal rate of medicine use in people with diabetes as it depends on clinical need, however, wide variation between DHBs or ethnic groups raises questions as to why that might be.

The Laboratory Collection includes tests performed in the community. The exclusion of hospital and point-of-care tests will under-count testing and may affect results more in some DHBs than in others.

Analysis does not split by type of diabetes

There were some limitations as to what measures could be presented here. It was not possible to reliably split people by type of diabetes; hence the indicators represent a combination of those with type 1 and type 2 diabetes. Generally, most people with diabetes aged 0–24 years will have type 1 diabetes, while around 90+ percent of those aged 25 years and over are expected to have type 2 diabetes.

The method used in the Virtual Diabetes Register to identify people with diabetes is less accurate at identifying children than adults with diabetes. A recently published survey highlights that local DHB data may be a better source for identifying prevalence in children: additional work is currently in hand.

Some important outcome indicators could not be included

Limitations of currently available data mean it was not possible to explore certain outcome indicators, including screening for diabetic retinopathy, retinopathy rates and end-stage renal failure. Outcome indicators, including myocardial infarction rates, stroke and other cardiovascular outcomes, are not included in this iteration of the Atlas, but are likely to be included in future updates. Users are encouraged to investigate local data in relation to these outcomes. 

References

  1. Hill K external link, Ward P external link, Grace BS external link, Gleadle J external link. Social disparities in the prevalence of diabetes in Australia and in the development of end stage renal disease due to diabetes for Aboriginal and Torres Strait Islanders in Australia and Maori and Pacific Islanders in New Zealand. BMC Public Health. 2017 Oct 11;17(1):802. 

Recommended reading/Suggested links

Last updated 11/01/2018