It is time for a more targeted approach to prediabetes in primary care in Aotearoa New Zealand

Abstract

Type 2 diabetes (T2DM), its related morbidities and entrenched diabetes‐related inequities pose significant challenges for health care delivery systems in Aotearoa New Zealand (NZ). Primary care services undertake the majority of diabetes prevention work by initially detecting and managing those with prediabetes. In this viewpoint, we present available NZ data to highlight NZ trends in prediabetes and consider the current NZ clinical guidelines and the prediabetes care pathway. Multiple areas for improvement are identified to optimise diabetes prevention, potentially reduce T2DM inequities, and sustain more effective prediabetes management in primary care in NZ.

Introduction

Type 2 diabetes mellitus (T2DM) is increasingly common in Aotearoa New Zealand (NZ), and substantial inequities in care exist for those of Māori, Pacific or Asian ethnicity.¹ Crucially, T2DM is 2.6-fold more likely to occur in the most deprived compared with the least deprived groups in NZ.¹ The detection of prediabetes provides an early opportunity to intervene to prevent or delay the onset of T2DM and associated morbidities. Although extensive research supports the efficacy of long-term lifestyle interventions in those with prediabetes,^2–6 individuals find adopting and sustaining lifestyle changes difficult.^7–12 These interventions are time-intensive and challenging for health providers to deliver.³ In NZ, primary care clinicians identify uncertainties about who is most likely to progress to T2DM and question when and how to intervene effectively.^13,14 They struggle to fit prediabetes care into time-constrained appointments.^13,14 Finding effective responses to these issues is critical for effective diabetes prevention and health equity.

Prevalence and epidemiological trends related to prediabetes in NZ

NZ lacks up-to-date national data on the prevalence of prediabetes, which is classified as glycated haemoglobin (HbA_1c) ≥ 41–49 mmol/mol or fasting glucose 6.1–6.9 mmol/L or 2-h glucose tolerance test 7.8–11.0 mmol/L. However, crude prediabetes estimates for the population aged ≥15 years from the Auckland Metropolitan region are 26% (2014) and approximately 21% in 2021 (pers. comm., Wing Cheuk Chan, Te Whatu Ora Counties Manukau). Most of these people would have been diagnosed using HbA1c, and the rate of undetected prediabetes is unknown. Māori and Pacific Peoples have higher rates of prediabetes,¹⁵ developing it at a younger age than others, with relative risks for Māori and Pacific versus non-Māori/non-Pacific of 1.97 for those aged <50 years and 1.42 for those aged ≥50 years.¹⁶ Similarly, the rates of prediabetes among NZ youth and children appear to be increasing in line with the rising rates of T2DM in these populations.¹⁷ For example, among adolescents with obesity (body mass index (BMI) ≥ 30 kg/m²), 53% had prediabetes,¹⁸ and recently, 16% of NZ children aged 8–12 years were found to have prediabetes.¹⁹ At a population level, the prevalence of T2DM and prediabetes increases with age;⁴ however, conversely, longer exposure to elevated glucose levels puts those who develop prediabetes/T2DM earlier in life at greater risk for adverse outcomes.^20,21

Prediabetes-related health outcomes

The likelihood of progressing from prediabetes to T2DM is variable. One NZ study²² found 5.0% (95% CI: 4.53–5.42) of adults with prediabetes developed T2DM over 3 years. Progression was greater in men, younger people, and those with higher HbA_1c and BMI levels. Specifically, those aged 35–44 years progressed three-fold more frequently than those aged >65 years. Baseline HbA_1c and BMI were both independently associated with progression to diabetes with dose-response relationships: HbA_1c (41 vs 49 mmol/mol) relative risk (RR) 55.6, [95% CI, 33.3–90.9]; and BMI (<25 vs 40+ kg/m²) RR 3.68 [95% CI, 1.39–9.72]. Although overall progression rates were greater in Māori and Pacific peoples, this was explained by higher baseline HbA_1c. Importantly, these data are limited to 3 years, and progression was higher among groups outside the sex/ethnic/age criteria for cardiovascular risk assessment (CVRA). Therefore, a reliance on screening for prediabetes that routinely occurs as part of CVRA processes may miss higher-risk groups most needing interventions. At the opposite end of the age spectrum, a prospective cohort study of older adults with prediabetes in the United States found many more regressed to normal glucose control or died from other causes than progressed to T2DM and, therefore, one would question the value of this diagnosis for those who are of an older age.²³ These differences between younger and older adults with prediabetes likely reflect the heterogeneous pathogenesis of T2DM and have important implications for targeting interventions.²⁴

Arguably, the name ‘prediabetes’ is unhelpful, as it may foster the perception that this condition only confers an increased risk for developing T2DM. However, those with prediabetes are also at increased risk of developing cardiovascular disease (CVD) and renal disease without frank T2DM. We found no published NZ data on this; however, a recent UK study examined outcomes related to HbA_1c 39–48 mmol/mol over 11 years and found a gradual increase of CVD and renal disease across the spectrum of HbA_1c levels, with most disease occurring in those with HbA_1c <48 mmol/mol. More than 66% of those with prediabetes who developed CVD or renal disease did not develop T2DM.²⁵ Our exploratory NZ study²⁶ found that 74% of a small sample (n = 153) of adults with prediabetes had metabolic syndrome, and there was considerable variability in the severity of this condition. Together, these findings are a timely reminder of the artificial nature of diagnostic cut-off points and the importance of assessing a comprehensive range of risk factors in those with prediabetes.

Current guidance

Current NZ clinical guidelines suggest a ‘one-size-fits-all’ approach to prediabetes management in primary care. All adults with prediabetes should receive lifestyle modification advice, metformin may be prescribed, and the active management of CVD risk factors is advised.²⁷ However, given the prevalence of prediabetes and the variability of risks indicated in the data reviewed above, we argue that this approach is inadequate and unsustainable for primary care, and a more refined approach is required.

Fig. 1 illustrates the current NZ prediabetes pathway based on the NZ clinical guidelines and the most frequent models of service provision within primary care settings. Using the data presented above, a critical review of the current NZ clinical guidelines, the views of primary care clinicians, and previous research, we identify limitations to implementing high-quality and targeted prediabetes care across the pathway.

[Image omitted: See PDF]

There are numerous opportunities to improve diabetes prevention work, which requires work at multiple levels. Table 1 identifies and suggests potential changes needed at policy, practice, and research levels to improve diabetes prevention in NZ.

[Image omitted: See PDF]

Conclusion

Prediabetes is common, affecting 21–26% of adults; however, the associated health risks are multifaceted, highly variable, and not fully understood in NZ populations. Current prediabetes guidelines and management pathways do not reflect this variability. Māori and Pacific Peoples are particularly poorly served and yet have high health needs in this area. Current guidelines are poorly optimised for targeting interventions and addressing the sustainability of service delivery within primary care. Widespread and multilevel change is urgently required to address these issues and reduce diabetes-related health inequities.

Data availability

The primary source of data for this paper are published in academic literature.

Conflicts of interest

The authors declare no conflicts of interest.

Declaration of funding

Christine Barthow was supported by a University of Otago Postgraduate Publishing Bursary.

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