Data for this analysis are derived from two previous studies [13, 15] that were approved by the University Biomedical Ethics board and the northern health regions, and that received written permission from the superintendents of the school districts and the principals of the five participating high schools. A detailed description of the study methods is published elsewhere [13]. Common procedures were employed in the two studies. Before any contact with potential participants, a letter was sent home to inform the adolescents and parents of the purpose and procedures of the study, confidentiality, and their right to withdraw. Then, at each school, the school principal and the Principal Investigator (PI) of the study visited all of the classes to explain the study and invite all students to participate. During these classroom visits, the students were reassured that they were not required to participate and refusal would not jeopardize their course standing. Written parental consent and student assent were obtained from each participant aged ≤17. Adolescents aged ≥18 were granted permission by the ethics board and school districts to provide their own consent. The PI and three Registered Nurses (RNs) conducted the diabetes and risk factor screening in a quiet room within the participating high schools.
Design
Adolescents who live in Western Canada were screened for prevalence of undiagnosed prediabetes and type 2 diabetes and the associated risk factors. Identification of risk for prediabetes and type 2 diabetes was assessed through the collection of demographic data, family history, anthropometric measurements, blood pressure (BP), and hemoglobin A1c (HbA1c) blood glucose levels.
The sample
The sample included high school students from three northern and remote Canadian predominantly Indigenous communities (n = 143) and from two urban high schools in a mid-sized (~ 250,000 population) western Canadian city (n = 253) who were assessed for risk for prediabetes and type 2 diabetes. The response rates for each school are reported in Table 1. No participants withdrew from the study. Qualifying criteria included adolescents who were 14–19 years old, enrolled in at least one class at the participating high schools, and present on the day of data collection. Exclusion criteria included a previous diagnosis of diabetes, non-English speaking, or being unable to provide consent as determined by the RN on initial contact. Only one participant was excluded due to a previous Type 1 diabetes diagnosis.
Anthropometry, blood pressure, and diabetes measurements
Anthropometric measurements including weight and height were assessed and used to calculate body mass index (BMI) [16]. Following World Health Organization [17] guidelines, BMI was interpreted as standard deviations and percentiles in relation to age and sex. Those with a BMI greater than 1 standard deviation for their age were considered overweight and those with a BMI greater than 2 standard deviations for their age were considered obese.
Blood pressure was measured manually by an RN using a standard clinical sphygmomanometer. For adolescents ≤17 years, hypertension was defined as a mean systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) at or above the 95th percentile for sex, age, and height [18]. Those with an SBP or DBP measured at or greater than the 90th percentile but less than the 95th percentile were considered to have prehypertension. For those who were ≥ 18 years old, abnormal increases in BP were defined as follows: mean SBP ≥ 140 mmHg or DBP ≥ 90 mmHg was high/hypertensive and mean SBP of 130–139 mmHg and/or a DBP of 85–89 mmHg was prehypertensive [19].
A validated cobas hemoglobin A1c (HbA1c) point of care test assay test was used to assess blood glucose levels [20]. Diabetes Canada criteria were used to classify adolescents into normal, high risk, prediabetes, and type 2 diabetes categories [21]. HbA1c levels < 5.5% (36 mmol/mol) were considered normal, 5.5–5.9% (37–41 mmol/mol) were considered high risk for diabetes, 6.0–6.4% (42–46 mmol/mol) were considered prediabetic, and above 6.5% (48 mmol/mol) were classified as type 2 diabetic [21, 22]. Any participant who presented with an HbA1c level ≥ 5.5% (37 mmol/mol) was referred to a physician for further investigation and other recommended tests to diagnose prediabetes and type 2 diabetes.
Other risks factors for the development of type 2 diabetes included in the screening were demographic data and a history of diabetes in a first- or second-degree relative. The adolescents were asked about their age, gender with which they identify, ethnicity, and personal medical history of diabetes.
The current literature suffers from significant disparities regarding the terms used to define ethnic groups. This study defines ethnicity on the basis of cultural characteristics, such as shared language, ancestry, religious traditions, dietary preferences, and history [23]. Those who self-identify as Indigenous include First Nations (North American Indian), Métis, or Inuit peoples, and/or those who registered under the Indian Act of Canada, and/or those who report membership in a First Nation or Indian band [24]. The term European defines adolescents who are of European descent, and are non-minority and/or Caucasian; and the term Filipino defines those who were born in and/or immigrated from the Philippines.
Analysis
Descriptive and inferential statistics were computed using the Statistical Package for Social Sciences (SPSS v.22.0, IBM, New York, USA) to establish risk and prevalence for prediabetes and type 2 diabetes in the adolescent sample. Additionally, chi-square analyses were conducted to investigate if the risk factors of hypertension, obesity, and family history occurred at higher frequencies in certain ethnicities. Comparisons were not reported with the African, and Asian, and “other” (defined below) categories due to small group sizes. Pairwise comparisons were also conducted along with Bonferroni corrections. Significant chi-square comparisons between the three groups (European, Indigenous, and Filipino) were identified. For each significant pairing, an odds ratio and confidence interval were calculated.