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The New Zealand Medical Journal

 Journal of the New Zealand Medical Association, 17-December-2004, Vol 117 No 1207

Preventing diabetes—time is running out
Robert Scragg
These days we are continually bombarded in the popular press about the current obesity epidemic and the resulting tidal wave of diabetes expected soon to cover Aotearoa (New Zealand). Indeed, despite predictions of an 80% increase in the number of people with diabetes during the 15 year period from 1996 to 2011,1 a degree of apathy and indifference appears to prevail among influential circles in the Ministry of Health and District Health Boards, creating the impression that these organs of Government believe there is plenty of time left to put diabetes preventive strategies in place and that urgent measures are not required.
The article by Tipene-Leach and colleagues,2 in this issue of the Journal, comes as a wake up call—to everyone—that time is running out. The very high prevalences of insulin resistance among Maori from the east coast north of Gisborne, particularly in young adults below 40 years of age, indicate that the main pathophysiological precursor of type 2 diabetes is already well-established in our midst.
The study is the first within New Zealand to document the prevalence of insulin resistance in a community sample, using the authors own method based on fasting insulin and triglycerides, which has higher sensitivity and specificity compared with other population measures of insulin resistance.3 Half (51%) of participants aged 25–39 years in this survey had insulin resistance (including diabetes).
As a check, the authors calculated the prevalence of the metabolic syndrome in their sample using the United States’ (US) Adult Treatment Panel III definition;4 which was 34% in the 25–39 year age group, much higher than 12–14% reported for 30–39 year old participants in the 3rd National Health and Nutrition Examination Survey from the US.5
Can the results from this East Coast study be applied to Maori across the whole of New Zealand? The relatively small sample size (n=247) means that confidence intervals (and the degree of uncertainty) around prevalence estimates are quite wide. Furthermore, the low response rate may have led to selection bias, but given that responders are usually healthier than non-responders, the survey may have actually under-estimated the prevalence of insulin resistance.
Indeed, the prevalence of obesity in this study (67% with body mass index (BMI)≥30) is higher than that reported for Maori in the 2002-2003 National Health Survey (about 30% with BMI≥32).6
If obesity is the only driver of insulin resistance, then it is quite likely that the prevalence of insulin resistance is lower among the wider Maori community than reported in this paper. A south Auckland cross-sectional survey has previously reported higher insulin levels in Maori (and Pacific) people, compared with European, which are entirely due to ethnic differences in BMI.7 In contrast, the Workforce Survey showed that the diabetes prevalence in Maori remained elevated after adjusting for BMI.8 So it is possible the very high insulin resistance prevalences reported in the study by Tipene-Leach and colleagues may not be due exclusively to the very high obesity levels in their study sample.
Other possible lifestyle factors contributing to the high prevalence of insulin resistance among Maori in this survey include: a diet high in animal fats, a risk factor for diabetes9 which is increased in Maori (and Pacific people) compared with Europeans ;10 and decreased physical activity—although nationally, Maori are more likely to do regular physical activity than other ethnic groups.6
As the study authors rightly conclude, a national survey of diabetes and insulin resistance is urgently required to confirm whether the very high prevalences of insulin resistance reported in their study occur more widely across New Zealand in Maori and in others who are also at high risk of diabetes such as the Pacific and Asian communities.
If very high prevalences of insulin resistance do occur in these ethnic groups, then the Ministry of Health and District Health Boards have a huge problem on their hands, with much bigger consequences than those they are trying to prevent via the multi-million dollar meningococcal vaccination campaign currently underway in the North Island.
The Ministry of Health is to be lauded for driving through its ‘Get Checked’ programme to improve the clinical management of diabetes by providing free annual medical checks to diabetes patients. It now needs to show the same conviction (and funding) towards implementing programmes for preventing diabetes.
The recent PricewaterhouseCoopers report shows that the health cost savings from a diabetes prevention programme are likely to be greater than programme itself.11 While there has been some investment by the Ministry of Health and District Health Boards into the development of diabetes prevention programmes, it is miniscule compared to funding of prevention programmes for other diseases, such as meningococcal meningitis and cancer screening.
The high levels of insulin resistance among young adults reported in the article by Tipene-Leach and colleagues indicates there is little time left to implement preventive strategies on a national basis. Continuing failure by the Ministry of Health to commit the funds required now for diabetes prevention will result in much greater health costs downstream, than currently, and many more people will suffer with diabetes.
Author information: Robert Scragg, Epidemiology & Biostatistics, School of Population Health, University of Auckland, Auckland
Correspondence: Assoc Prof Robert Scragg, Epidemiology & Biostatistics, School of Population Health, University of Auckland, Private Bag, Auckland. Fax: (09) 373 7624; email: r.scragg@auckland.ac.nz
References:
  1. Tobias M, Cheung J. Modelling diabetes: a summary. Wellington: Ministry of Health, Public Health Intelligence, Occasional Bulletin No 11, 2002; Available online. URL: http://www.moh.govt.nz/moh.nsf/0/baae3c671db244cfcc256b76000bed88?OpenDocument Accessed December 2004.
  2. Tipene-Leach D, Pahau H, Joseph N, Coppell K, McAuley K, Booker C, Williams S, Mann J. Insulin resistance in a rural Maori community. N Z Med J. 2004;117(1207). URL: http://www.nzma.org.nz/journal/117-1207/1208
  3. Ascaso JF, Pardo S, Real JT, et al. Diagnosing insulin resistance by simple quantitative methods in subjects with normal glucose metabolism. Diabetes Care. 2003;26:3320–5.
  4. National Cholesterol Education Program. Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 2002;106:3143–421.
  5. Ford ES, Giles WH, Dietz WH. Prevalence of the metabolic syndrome among US adults: findings from the third National Health and Nutrition Examination Survey. JAMA. 2002;287:356–9.
  6. Ministry of Health. A portrait of health: key results from the 2002/03 New Zealand Health Survey. Wellington: Ministry of Health; 2004. Available online. URL: http://www.moh.govt.nz/moh.nsf/0/3d15e13bfe803073cc256eeb0073cfe6?OpenDocument Accessed December 2004.
  7. Simmons D, Thompson CF, Volkander D. Polynesians: prone to obesity and Type 2 diabetes but not hyperinsulinaemia. Diabetic Med. 2001;18:193–8.
  8. Scragg R, Baker J, Metcalf P, Dryson E. Prevalence of diabetes and impaired glucose tolerance in a New Zealand multi-racial workforce. N Z Med J. 1991;104:395–7.
  9. Fung TT, Schilze M, Manson JE, et al. Dietary patterns, meat intake, and the risk of Type 2 diabetes in women. Arch Intern Med. 2004;164:2235–40.
  10. Metcalf PA, Scragg RKR, Tukuitonga CF, Dryson EW. Dietary intakes of middle-aged European, Maori and Pacific Islands people living in New Zealand. N Z Med J. 1998;111:310–3.
  11. PricewaterhouseCoopers. Type 2 diabetes: managing for better health outcomes. Wellington: Diabetes New Zealand; 2001. Available online. URL: http://www.diabetes.org.nz/resources/pwcreport.html Accessed December 2004.


     
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