Participants: Primary ascertainment was from the Australasian Paediatric Endocrine Group NSW Diabetes Register, with secondary ascertainment from the National Diabetes Register (Australian Institute of Health and Welfare).
Results: There were 128 incident cases of T2DM (62 boys, 66 girls) in the study period. The median age at diagnosis was 14.5 years (interquartile range, 13.0–16.4), and 90% were overweight or obese (body mass index > 85th percentile for age). Mean annual incidence was 2.5/100 000 person-years (95% CI, 2.1–3.0) in 10–18-year-olds. Of the ethnic groups represented, white Australian comprised 29%, Indigenous 22%, Asian 22%, North African/Middle Eastern 12% and Māori/Polynesian/Melanesian 10%. The incidence of T2DM was significantly higher in the Indigenous than the non-Indigenous group (incidence rate ratio, 6.1; 95% CI, 3.9–9.7; P < 0.001), but incidence rates of T1DM were similar (15.5 v 21.4/100 000, respectively).
Conclusions: T2DM accounts for 11% of incident cases of diabetes in 10–18-year-olds, and the majority are overweight or obese. The high rate among Indigenous Australian children supports screening for T2DM in this population.
The recent global increase in incidence of type 2 diabetes mellitus (T2DM) in children and adolescents1 has been attributed to environmental factors (eg, changes in lifestyle and eating habits), and parallels the increase in childhood obesity.2-4 In the United States, from 1999 to 2004, the proportion of T2DM among new-onset diabetes in children and adolescents increased from < 3% to 45%.1 Similar trends have been found in New Zealand4 and Western Australia.5
Accompanying the increased case-load of T2DM is a greater risk of early complications — microalbuminuria, hypertension and dyslipidaemia — than with type 1 diabetes mellitus (T1DM).6-8 Young people with T2DM may also have other significant medical conditions, global developmental delay or psychiatric disease.5,8,9
Although indigenous groups in other countries are reported to be at high risk of developing childhood-onset T2DM,10,11 there are limited population-based data on T2DM among Australia’s young Indigenous population.5,12 The WA study found a higher incidence of T2DM among Indigenous compared with non-Indigenous children.5 We aimed to determine the population-based incidence of T2DM in New South Wales, in 2001–2006, among Indigenous and non-Indigenous young people and the characteristics of T2DM at diagnosis.
The notification method for the Australasian Paediatric Endocrine Group NSW Diabetes Register, described previously,13,14 was adapted to ascertain incident cases of T2DM from 1 January 2001. This included wider distribution of the revised notification form, newsletters and presentations, to increase awareness of the change. Secondary ascertainment was from the National Diabetes Register (NDR) (Australian Institute of Health and Welfare), which ascertains cases of insulin-treated diabetes from the National Diabetes Supply Scheme (NDSS). Patients give consent for inclusion on the NDR at the time of registration for the NDSS (ascertainment rate, 92% in 200415). Overall ascertainment for incident cases using both sources is more than 99%.13,14
T2DM was diagnosed according to the American Diabetes Association criteria, which include the presence of acanthosis nigricans, negative test results for diabetes-associated autoantibodies, and elevated fasting insulin or C-peptide levels.16 Register inclusion criteria were: age, 0–18 years at diagnosis; usual place of residence, NSW; and diagnosis, 1 January 2001 to 31 December 2006. Patients with secondary diabetes (eg, cystic fibrosis or hyperinsulinism) or genetic β-cell defects (“maturity onset diabetes of the young”) were excluded.
Incident cases of T2DM were reported to the register by paediatricians, physicians, paediatric endocrinologists, endocrinologists, diabetes educators, and nurses. Informed consent was obtained from parents of children and adolescents enrolled in the register. The study was approved by the ethics committees of The Children’s Hospital at Westmead and participating hospitals.
Clinical details at diagnosis were obtained from medical record review and by physician questionnaire. Characteristics obtained included anthropometric data, ethnic background (Australian Bureau of Statistics [ABS] criteria),17 family history of diabetes, investigation results (including for diabetes-associated autoantibodies), and treatment at diagnosis. Postcode of residence at diagnosis was used to distinguish between urban and rural residence using ABS data.18
Population estimates for children in NSW19 and for Indigenous children were obtained from the ABS. Mean annual incidence of T2DM was calculated per 100 000 person-years for 10–18-year-olds over the 6-year period. For comparison, T1DM incidence rates in young people aged 10–18 years, and in Indigenous young people, were estimated over the same period by the same methods. Confidence intervals were calculated assuming a Poisson distribution.20 Poisson regression models were used to analyse incidence rates and to investigate trends in incidence, with outcomes expressed as incidence rate ratios and 95% CIs. Statistical analysis was performed using SPSS, version 14.0 (SPSS Inc, Chicago, Ill, USA) and Stata, version 8.0 (StataCorp, College Station, Tex, USA).
There were 128 incident cases of T2DM in children and adolescents aged 7–18 years from 2001 to 2006 inclusive (62 boys, 66 girls). The mean annual incidence estimated for 10–18-year-olds (there were only seven children aged 7–9 years) was 2.5 per 100 000 person-years (95% CI, 2.1–3.0). Incidence did not change over the 6-year period (incidence rate ratio [IRR], 0.99; 95% CI, 0.89–1.09). The mean annual incidence of T1DM in 10–18-year-olds over the same period was 21.1 per 100 000 (95% CI, 19.9–22.5). Overall, 11% of incident cases aged 10–18 years had T2DM.
The median age at diagnosis of T2DM was 14.5 years (interquartile range [IQR], 13.0–16.4), and the youngest was 7.5 years. The median body mass index (BMI) was 31.1 kg/m2 (IQR, 26.1–36.7), and the median BMI SD score was 2.2 (IQR, 1.7–2.8), with 90% of patients either overweight or obese (BMI > 85th percentile for age).
There were more urban residents among incident cases (66% were from the Sydney Statistical Division). Incidence was significantly higher in the North Western Statistical Division of NSW (8.8 per 100 000 [95% CI, 3.8–17.3]) versus urban Sydney (2.6 per 100 000 [95% CI, 2.0–3.2]); IRR, 3.5 (95% CI, 1.7–7.2; P = 0.001). Among patients for whom ethnicity was available (n = 105; 82%), 29% were white Australians, 22% Indigenous, 22% Asian, 12% North African/Middle Eastern, 10% Māori/Polynesian/Melanesian, 5% European, and the remaining were African or South American. Among those with T1DM for whom ethnicity was available (n = 747; 72%), 4% identified as Indigenous. The incidence of T2DM was significantly higher in Indigenous than non-Indigenous young people, while the incidence of T1DM was similar (Box 1). The characteristics of Indigenous young people with T1DM and T2DM are given in Box 2.
Over the period 2001–2006, 11% of 10–18-year-olds with newly diagnosed diabetes in NSW had T2DM. While the caseload for T2DM was lower than for T1DM, more than half the patients were from minority groups and most were overweight or obese. The incidence of T2DM in Indigenous young people (12.7/100 000) was more than six times higher than that in the non-Indigenous group, in keeping with data from WA, where incidence ranged from about 8 to 16 per 100 000 from 1997 to 2002.5
These are the first population-based diabetes incidence data reported for Indigenous children and adolescents in NSW. Although T2DM incidence was higher in the Indigenous than the non-Indigenous group, characteristics such as age at diagnosis, sex and BMI SD score were similar.
That the incidence of T1DM was similar in NSW Indigenous and non-Indigenous children and adolescents is initially surprising, because there is a greater than 300-fold variation in T1DM incidence worldwide, with low rates in many indigenous populations.21 While the background risk for T1DM in Indigenous Australians is unknown, the high incidence supports the putative role of environmental factors (diet, lifestyle and infections) in T1DM.22
We may have underestimated the incidence of T2DM, particularly among older adolescents or children from remote areas who may not have access to paediatric diabetes services. The NDR only collects information on insulin-treated T2DM, so there may be additional unreported cases of T2DM not requiring insulin. However, based on our experience with the NSW Diabetes Register since 1990, with more than 99% overall case ascertainment,13,14 it is unlikely that T2DM incidence is significantly under-reported here. As ethnicity data were not available for all patients, it is possible that incident cases among Indigenous and minority groups were underestimated.
The high incidence of T2DM in Indigenous Australian children and adolescents, and those from other minority groups, supports consensus recommendations for screening high-risk groups, including overweight children (BMI > 85th percentile), those from high-risk ethnic backgrounds (Indigenous, Asian/Pacific and Hispanic), and those with signs of insulin resistance (acanthosis nigricans), or a family history of T2DM.21 The high rate of early complications5,6,8,23 and the more common occurrence of dyslipidaemia, hypertension and renal disease in Indigenous children make screening even more important.24 As Indigenous and non-Indigenous children and adolescents have similar rates of T1DM, both forms of diabetes should be considered in an Indigenous child presenting with diabetes, and testing for autoantibodies should be included in the diagnostic work-up.
1 Incidence per 100 000 (95% CI) of diabetes type 1 and 2 in Indigenous and non-Indigenous 10–18-year-olds, NSW, 2001–2006
2 Characteristics of Indigenous children diagnosed with diabetes type 1 and 2, NSW, 2001–2006
- 1. Pinhas-Hamiel O, Zeitler P. The global spread of type 2 diabetes mellitus in children and adolescents. J Pediatr 2005; 146: 693-700.
- 2. Likitmaskul S, Kiattisathavee P, Chaichanwatanakul K, et al. Increasing prevalence of type 2 diabetes mellitus in Thai children and adolescents associated with increasing prevalence of obesity. J Pediatr Endocrinol Metab 2003; 16: 71-77.
- 3. Wei JN, Sung FC, Lin CC, et al. National surveillance for type 2 diabetes mellitus in Taiwanese children. JAMA 2003; 290: 1345-1350.
- 4. Hotu S, Carter B, Watson PD, et al. Increasing prevalence of type 2 diabetes in adolescents. J Paediatr Child Health 2004; 40: 201-204.
- 5. McMahon SK, Haynes A, Ratnam N, et al. Increase in type 2 diabetes in children and adolescents in Western Australia. Med J Aust 2004; 180: 459-461. <MJA full text>
- 6. Ettinger LM, Freeman K, Dimartino-Nardi JR, Flynn JT. Microalbuminuria and abnormal ambulatory blood pressure in adolescents with type 2 diabetes mellitus. J Pediatr 2005; 147: 67-73.
- 7. Scott A, Toomath R, Bouchier D, et al. First national audit of the outcomes of care in young people with diabetes in New Zealand: high prevalence of nephropathy in Maori and Pacific Islanders. N Z Med J 2006; 119: U2015.
- 8. Eppens MC, Craig ME, Cusumano J, et al. Prevalence of diabetes complications in adolescents with type 2 compared with type 1 diabetes. Diabetes Care 2006; 29: 1300-1306.
- 9. Levitt Katz LE, Swami S, Abraham M, et al. Neuropsychiatric disorders at the presentation of type 2 diabetes mellitus in children. Pediatr Diabetes 2005; 6: 84-89.
- 10. Fagot-Campagna A, Pettitt DJ, Engelgau MM, et al. Type 2 diabetes among North American children and adolescents: an epidemiologic review and a public health perspective. J Pediatr 2000; 136: 664-672.
- 11. Dean HJ, Young TK, Flett B, Wood-Steiman P. Screening for type-2 diabetes in aboriginal children in northern Canada. Lancet 1998; 352: 1523-1524.
- 12. Braun B, Zimmermann MB, Kretchmer N, et al. Risk factors for diabetes and cardiovascular disease in young Australian Aborigines. A 5-year follow-up study. Diabetes Care 1996; 19: 472-479.
- 13. Craig ME, Howard NJ, Silink M, Chan A. The rising incidence of childhood type 1 diabetes in New South Wales, Australia. J Pediatr Endocrinol Metab 2000; 13: 363-372.
- 14. Taplin CE, Craig ME, Lloyd M, et al. The rising incidence of childhood type 1 diabetes in New South Wales, 1990-2002. Med J Aust 2005; 183: 243-246. <MJA full text>
- 15. Australian Institute of Health and Welfare. National Diabetes Register: impact of changed consent arrangements on ascertainment from the National Diabetes Services Scheme. Canberra: AIHW, 2006. (Diabetes Series No. 5, Catalogue No. CVD 35.)
- 16. American Diabetes Association. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 2003; 26 Suppl 1: S5-S20.
- 17. Australian Bureau of Statistics. Australian standard classification of cultural and ethnic groups (ASCCEG). Canberra: ABS, 2005. (Catalogue No. 1249.0).
- 18. Australian Bureau of Statistics. National localities index. Canberra: ABS, 2004. (Catalogue No. 1252.0.)
- 19. Australian Bureau of Statistics. Population estimates by age and sex, New South Wales by geographic classification [ASGC 2005]. Canberra: ABS, 2005. (Catalogue No. 3235.1.55.001.)
- 20. Haenszel W, Loveland DB, Sirken MG. Lung-cancer mortality as related to residence and smoking histories. I. White males. J Natl Cancer Inst 1962; 28: 947-1001.
- 21. Craig ME, Hattersley A, Donaghue K; International Society for Pediatric and Adolescent Diabetes. ISPAD Clinical Practice Consensus Guidelines 2006–2007. Definition, epidemiology and classification. Pediatr Diabetes 2006; 7: 352-360.
- 22. Craig ME, Howard NJ, Silink M, Rawlinson WD. Reduced frequency of HLA DRB1*03-DQB1*02 in children with type 1 diabetes associated with enterovirus RNA. J Infect Dis 2003; 187: 1562-1570.
- 23. Eppens MC, Craig ME, Jones TW, et al. Type 2 diabetes in youth from the Western Pacific region: glycaemic control, diabetes care and complications. Curr Med Res Opin 2006; 22: 1013-1020.
- 24. Mackerras DE, Reid A, Sayers SM, et al. Growth and morbidity in children in the Aboriginal Birth Cohort Study: the urban-remote differential. Med J Aust 2003; 178: 56-60.
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