Diabetes in the Cook Islands: a clinical audit

Introduction

The global burden of diabetes mellitus (diabetes) is a significant public health threat with approximately 537 million adults living with diabetes.¹ Diabetes is broadly categorised as type 1 diabetes, where an individual has a deficient level of insulin secretion or type 2 diabetes, the cause being a combination of resistance to insulin and/or inadequate levels of insulin secretion in response to glucose in the blood stream. Previous studies have shown an increase in the prevalence of people with prediabetes who are at risk of developing diabetes.² Prediabetes is defined as having a higher level of blood sugar than normal, but lower than the diabetes threshold.³ There are three substitutable criteria for diagnostic screening of prediabetes that include fasting plasma glucose (FPG, 5.6–6.9 mmol/L), 2-h plasma glucose (2-h PG, 7.8–11.0 mmol/L), and haemoglobin A1c 5.7–6.4% (HbA1c, 39–47 mmol/mol).⁴ In New Zealand, one of the criteria of prediabetes diagnosis is a fasting glucose range of 6.1–6.9 mmol/L;⁵ therefore, diabetes is diagnosed if either the HbA1c is ≥50 mmol/mol, fasting glucose is ≥7 mmol/L or the random glucose is ≥11.1 mmol/L.⁶ The Cook Islands medical guidelines are similar to New Zealand guidelines in terms of diabetes diagnosis criterion.⁷

It is evident that there is an increase in the prevalence of gestational diabetes mellitus (GDM) observed in women when signs of glucose tolerance are shown.⁸ It is possible that the current obesity and diabetes epidemic has resulted in a higher proportion of women of childbearing age with type 2 diabetes, consequently resulting in an increase in the number of mothers with GDM.⁹ In a study conducted among pregnant women in their second trimester in Rarotonga, 646 women were reported to have glucose challenges in a 4 -year period (January 2009 to December 2012).¹⁰

The global burden of diabetes is a significant public health issue that impacts differentially on vulnerable populations, with three-quarters of adults living with diabetes residing in low- and middle-income countries.¹ The global economic burden of diabetes and its related complications is substantial and projected to reach USD 2.1 trillion in 2030.¹¹ The global direct health expenditure on diabetes is estimated to be USD 760 billion and is projected to increase to USD 845 billion by 2045.¹² In Pacific Island countries and territories, non-communicable diseases (NCD; mostly cardiovascular disease, diabetes, cancer and chronic respiratory disease), account for more than 70% of deaths.¹³ In a World Health Organization (WHO) surveillance survey of NCD risk factors in some Pacific nations (2002–2011) almost half of the adult population in American Samoa had been diagnosed with diabetes compared to one-third in Niue and the Federated States of Micronesia, and one-quarter in the Cook Islands.¹³ Obesity as a risk factor for diabetes^14,15 was reported by more than 75% of adults in American Samoa, 63% in Niue and Tokelau, and 61% in the Cook Islands.¹³

The Cook Islands National Strategy and Action Plan for NCDs was developed in 2009 and has led to the development of the Cook Islands NCD Strategy 2015–2019.¹⁶ The strategy is operationalised through eight components, including integrated NCD activities; alcohol harm reduction; tobacco control; mental health and disability; food and nutrition; physical activities; national health system approach and monitoring; evaluation; and surveillance.¹⁶ These components were established in collaboration with relevant stakeholders and are the basis of all NCD activities. Programmes include promotion of healthy living at church services and youth groups, free health risk assessments at one’s place of employment, and smoking cessation services on the main island of Rarotonga.¹⁶ In the recent strategic action plan to prevent and control NCD during 2021–2025,¹⁷ the Cook Islands ministry takes steps in four domains: enabling national multi-sectoral action to expedite whole-of-country NCD prevention and control (e.g. establish community NCD committees); promoting and educating NCD patients, families and communities to prevent and control NCDs (e.g. establishing a NCD communications strategy, identifying the target audience, key messages, media platforms); reinforcing NCD preventive and control legislation and policy for effective action (e.g. promoting healthy food and nutrition); and providing access to quality and equitable health services for NCD patients and people at risk of NCDs (e.g. maintaining currency of the NCD register). For instance, evidence-based profitable interventions for people with diabetes in this action plan includes offering glycaemic control, providing preventive foot care, as well as screening diabetes patients for retinopathy and providing laser photocoagulation to prevent blindness.¹⁷

Therefore, evidence-based studies could promote our knowledge of better screening and providing services for NCD patients and people at risk of NCDs (e.g. diagnosis and diabetes management). Furthermore, in a bigger picture, such documents could help direct policies and medical services to improve public health. Although global and regional information systems suggest that the burden of diabetes is high, inadequate surveillance systems in the Pacific region and the Cook Islands have hindered the ability for countries to quantify the burden of diabetes and subsequently mount an effective response. The aim of this audit is to examine the prevalence of diabetes and pre-diabetes and the incidence of GDM in the Cook Islands during 1967–2018.

Methods

The Cook Islands consists of 15 islands dispersed over 2 million km² of the South Pacific Ocean and is geographically divided into the Southern and Northern group islands.^16,18 According to the 2016 population census, the population was 17 434 with over three-quarters living on the main island of Rarotonga. The Cook Islands is part of the Realm of New Zealand and maintains a strong relationship with the New Zealand Government.¹⁹ Te Marae Ora Cook Islands Ministry of Health acts on behalf of the Cook Islands Government to deliver publicly funded health services.

We analysed the Cook Islands NCD register, which is maintained on the Ministry Patient Information System (MedTech) and holds all available data from 1967 to 1931 December 2018. We sought information regarding the demographic characteristics of registered patients with all types of and pre-diabetes. This included the date when diabetes or prediabetes was diagnosed. We also analysed the Cook Islands GDM register, which is a subset of the NCD register and is administered by the Obstetrics and Gynaecology service, for the period of 2009–2018.

As part of the data quality assessment process, we sought additional data from MedTech using the pre-determined Classification Read Code for Diabetes. Data sets were extracted to Microsoft Excel and two reviewers verified the data examining for completeness, accuracy and consistency, and correcting these on the Microsoft Excel sheet as necessary. Once validated as correct, revised information was updated directly to the patients’ clinical notes and classifications section on MedTech.

Patients were included in the study if they were alive, living in-country, and regularly receiving medical or nursing care for diabetes or pre-diabetes. All cases who were deceased or had moved overseas were excluded. Patients with pre-diabetes have been included, as the majority would have been registered with the diabetes clinic and therefore received dietary and lifestyle advice, with a few receiving metformin.

This study was conducted as part of a 6-week summer studentship provided through the Health Research Council of New Zealand Pacific scholarship. Data analysis was conducted using Microsoft Excel and STATA15 software (StataCorp, College Station, TX, USA). The data were properly anonymised and confidentiality of information was assured. Ethics approval was obtained from the University of Auckland Human Subjects Committee (Reference 020659) and the Cook Islands National Research Committee.

Results

For all recorded data over the period of 1967–2018, 1270 diabetes cases were registered on the Cook Islands Non-Communicable Diseases database. In addition, there were 54 pre-diabetes cases and 146 patients diagnosed with gestational diabetes from January 2009 to December 2018.

Frequency of diabetes cases diagnosed by year

The number of diabetes cases has increased over time, with a gradual increase in numbers observed in the early 1990s, followed by rapid acceleration after 2000 (Fig. 1). As the Fig. 1 shows, there were two major peaks in 2008 and 2016.

Fig. 1. 

Cook Islands diabetes mellitus (diabetes) register 1967–2018 – the trend of diabetes cases diagnosed by year (n = 1270).

Frequency and age at diagnosis of diabetes cases diagnosed by year

Regarding age of the case at the time of diagnosis, an increasing number of diabetes cases was observed from the age of 25 years, which peaked around age 55 years, before declining (Fig. 2).

Fig. 2. 

Cook Islands diabetes mellitus (diabetes) register 1967–2018 – number and age at diagnosis of diabetes cases diagnosed by year (n = 1270).

Frequency of births and GDM cases by year

Based on Fig. 3, for the years 2009–2018, 146 cases of gestational diabetes were diagnosed. Of these, 11 women had two pregnancies and were diagnosed with GDM, whereas four women had three pregnancies and were diagnosed during this period. Of these, three were diagnosed with diabetes within 2 years. Of all those diagnosed with GDM, 20 were eventually diagnosed with Type 2 diabetes. The average age at diagnosis was 37 years, with at least 80% diagnosed before the age of 40 years. On average, there are 260 births per year in the Cook Islands and about 14 GDM cases diagnosed. As Fig. 3 shows, GDM cases had two significant peaks in 2009 and 2012.

Fig. 3. 

Cook Islands GDM register 2009–2018 – number of births and GDM cases (n = 146), by year.

Discussion

The burden of diabetes in the Cook Islands is significant, with 1270 diabetes cases diagnosed over the past decades. The rates of diabetes and prediabetes are higher among women and people aged between 45 and 64 years. Women with gestational diabetes (mean age = 37 years) are significantly at risk of developing diabetes after pregnancy. The prevalence of diabetes is increasing in the Cook Islands, affecting those aged from 45 to 64 years, reflecting similar trends globally.¹

Although there were a few pre-diabetes cases diagnosed, given the number of diabetes cases and GDM cases, this study suggests that it is likely that many pre-diabetes cases that have not been further diagnosed. In the Cook Islands, most antenatal women are screened for diabetes during pregnancy. There is no systematic diabetes screening undertaken for the general population. Inconsistent with some previous research in the Pacific,^21–23 the current findings show a decrease in GDM prevalence among people in the Cook Islands. This inconsistency in results could possibly be linked to immigration of young people from the Cook Islands. In part, a decreasing population since 2006–2021 (19 342–15 040 people) might play a role in reducing the rate of GDM.²⁰

With the large proportion of young women developing diabetes during pregnancy and progressing to type 2 diabetes, urgent attention is required to understand the drivers and factors that could be responsible for this. The study findings suggest that perhaps screening for diabetes in Cook Islands women may have to begin at a younger age, and that more effort should be placed on raising awareness about the risks to both mum and baby, including information about foetal abnormalities and complications during childbirth. These findings also relate to a qualitative research paper²⁴ that examines prediabetes for the Tongan population in New Zealand in which the age of newly diagnosed women with prediabetes was reported at a younger age (20s and 30s).

Modernisation, migration, and urbanisation have impacted dietary intake and physical activity, thus driving the obesity epidemic, and the increase in NCDs in the Cook Islands.²⁵ Imported foods such as rice, sugar, canned foods, and sugar drinks have replaced traditional foods such as taro, fish, fruits, and vegetables due to the increased affordability and accessibility.²⁶ Consequently, more Cook Islanders are leading sedentary lifestyles, and fewer individuals are obtaining resources from the land due to the physically demanding activities associated with growing crops.^27,28 This could explain the rapid acceleration of the number of diabetes cases from 2000 onwards. Reduced physical activity level could result in obesity, which contributes to diabetes development.¹⁴

The findings from this study have also noted that young adolescents are also being diagnosed with type 2 diabetes. Previous studies also support these findings and have shown an increase in the number of diabetes cases among young adolescents that could be a result of global increasing obesity, contextual factors and/or genetics, gender, race, or physical activity level and insulin sensitivity.²⁹ In New Zealand, obesity and ethnicity (Māori and Pacific Island) were considered as factors of increasing prevalence of type 2 diabetes among adolescents.³⁰ In a more recent study,³¹ the risk of type 2 diabetes among young people was found to be associated with gender (being females) and being from high-risk ethnic groups (Māori and Pacific Island), and increased deprivation.

Poor data quality and limited data fields, and the lack of regular quality audits was apparent. Due to the limited time period of the study, severe time constraints were due largely to the time required to verify the datasets. Additionally, missing data for patients who had been referred, or who were deceased, reduced the ability to monitor progress. The Te Marae Ora Cook Islands Ministry of Health had no access to patient records once they were referred overseas. Missing data and inaccuracies in the reporting of results reduced the quality of data and increased the time required to analyse data appropriately.

The Cook Islands NCD register contains almost 7000 cases. When extracting data from the diabetes register, there were just over 2200 cases. However, during the verification process, it became clear that regular data quality audits had not been undertaken for some time. Subsequently, the register included deceased persons and those who were no longer residing in the Cook Islands. Did they die outside the study period, and reside outside the study period?

Diabetes threatens to undermine and reverse the social and economic development of the Cook Islands. This calls for urgent attention to address the drivers of diabetes that must also consider the social and economic factors that hinder preventative measures.

Conclusion

The prevalence of diabetes and pre-diabetes in the Cook Islands has increased progressively. The risk is disproportionately linked with gender and age (being female and an age range of 45–64 years). Young people also are considerably at risk of diabetes. Although the findings showed a decrease in the number of gestational diabetes mellitus cases, it has been reported that gestational diabetes mellitus could lead to other types of diabetes later in life. Consistent data collection and improving medical records are highly recommended to provide precise evaluations of the non-communicable diseases register trends and to help facilitate effective services and interventions.

Data availability

The data that support this study cannot be publicly shared due to ethical or privacy reasons but may be shared upon reasonable request to the corresponding author if appropriate.

Conflicts of interest

The authors declare no conflicts of interest.

Declaration of funding

We would like to thank the New Zealand Health Research Council Pacific Heath Summer studentship programme for funding this project.