Understanding vascular complications in children from type 1 diabetes diagnosis: protocol for a prospective cohort study in Vancouver, Canada

Abstract

Introduction

Cardiovascular disease is a major complication of type 1 diabetes (T1D). There is evidence of cardiovascular damage in children who have T1D but it is unclear how and when the cardiovascular damage begins. There is also minimal data on cardiovascular complications in children with T1D living in Canada. The goal of this project is to determine the timing and factors leading to vascular damage in children (aged 8–18 years) from T1D diagnosis.

Methods and analysis

This is a prospective longitudinal cohort study investigating vascular health in children through the first 2 years of T1D diagnosis living in Metro Vancouver, Canada. The primary outcomes of the study include changes in arterial stiffness (pulse wave velocity; Augmentation Index), clinic and 24-hour ambulatory blood pressure, and blood biomarkers of vascular damage. Secondary outcome measures include body composition, surrogate markers of adiposity (Body Mass Index, waist circumference), and nutritional assessment, physical activity, glycated haemoglobin (A1C), and to determine the relationships to measures of arterial stiffness, 24-hour ambulatory blood pressure and blood biomarkers of vascular damage. We will also collect sociodemographic data and pubertal status (Tanner staging). Assessments will be performed at diagnosis (within 14 weeks of T1D diagnosis; baseline) and at 6, 12, 18 and 24 months post-diagnosis.

Ethics and dissemination

This protocol has been approved by the University of British Columbia Clinical Research Ethics Board and the Children’s and Women’s Health Centre of British Columbia Research Ethics Board (H21-03109). Results will be disseminated through clinical and community presentations and peer-reviewed manuscripts. We will also present our findings to people living with T1D, such as the Young & T1 group.

Trial registration number

NCT05790785.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This is a prospective longitudinal cohort study.

• We use a comprehensive approach to examine the chronology of vascular damage in children from type 1 diabetes (T1D) diagnosis using state-of-the-art non-invasive methodologies.

• Vascular data will be captured using methods employed in other cohorts allowing for comparisons between different populations.

• We include nutritional assessment of the children to investigate dietary changes following T1D diagnosis and how this may impact vascular health in children.

• We recognise a limitation of the study is the small sample size but this reflects the number of children diagnosed with T1D in Vancouver.

Introduction

Population-based studies have identified a 10-fold higher age-adjusted relative risk of cardiovascular disease in adults with type 1 diabetes (T1D) compared with the general population.¹,⁵ T1D is an autoimmune disease that destroys insulin-producing pancreatic beta cells. It is the predominant form of diabetes in Canadian children⁶; worldwide, ~1.1 million children live with T1D.⁷ In Canada, an estimated 33 000 children and 300 000 adults have T1D.⁸ Adults with T1D experience cardiovascular events, such as myocardial infarction, coronary revascularisation and stroke, more frequently and at an earlier age.⁹ In fact, cardiovascular events are the leading cause of T1D-associated death.⁹,¹¹ The origins of vascular damage in T1D, and which pathways to target to prevent or reverse it, are not fully understood.

Children with T1D have typical cardiovascular risk factors such as dyslipidaemia, obesity and elevated blood pressure (BP), and early indicators of vascular damage, including endothelial dysfunction (loss of protective endothelial properties), arterial stiffening and greater carotid intima-media thickness (cIMT).¹²,³⁵ In our pilot study,³⁰ we found that 57% of children (n=57) with T1D had BP abnormalities (eg, prehypertension, hypertension, masked hypertension, non-dipping)³⁶ and elevated 24 hours systolic blood pressure (SBP) and diastolic blood pressure (DBP) indices. We observed no differences between children diagnosed for less than or equal to 2 years compared with those diagnosed for more than 5 years. Our data suggest that vascular damage may occur during the initial phase of the disease and causes chronic complications. Early prevention or reversal of T1D-associated vascular damage may lower the risk for (or prevent) future cardiovascular events.

Rather than being due to long-term disease, the burden of cardiovascular disease in adults with T1D may be associated with early vascular damage that occurs pre-T1D and post-T1D diagnosis. However, thus far, all published data on cardiovascular damage in children with T1D were collected ≥1 year after diagnosis.¹²,²⁶ There are no published studies on vascular damage at T1D diagnosis, how this progresses longitudinally in children, and whether early reversal will improve outcomes. Observational studies have reported vascular damage in children several years post-diagnosis.¹²,²⁶ Vascular endothelial dysfunction, commonly assessed by brachial artery flow-mediated dilatation (FMD), is an early indicator of vascular damage and atherosclerosis in adults.³⁷ Endothelial dysfunction is a key contributor to arterial stiffness.³⁸ Cross-sectional studies reported lower FMD in children (ages 8–15 years) with T1D for ~5 years (range 2–12 years) compared with age-matched and sex-matched children without diabetes.¹²,^{1418 23}

Arterial stiffness, often assessed by pulse wave velocity (PWV) or Augmentation Index (AIx), can precede BP elevations³⁹ and is an early indicator of atherosclerosis³⁸ and a predictor of cardiovascular events and mortality in adults.⁴⁰,⁴² Greater arterial stiffness was reported in children with T1D (mean age 12 years, disease duration 6 months to 5 years) compared with age-matched and sex-matched control children.¹³¹⁵,^{17 22} Carotid intima-media thickness is a progressive, subclinical indicator of atherosclerosis and predictor of cardiovascular mortality in adults.⁴³ Greater cIMT has been reported in children with T1D compared with age-matched controls.^{1417 19},^{21 26}

Vascular damage in children with T1D progresses over time. The SEARCH for Diabetes in Youth study and the ancillary SEARCH Cardiovascular Disease (CVD) study reported greater arterial stiffness²⁷ and cIMT³³ in children with T1D (mean age 14.6 years, disease duration 4.8 years) compared with healthy control children (mean age 17.8 years)³⁵; the differences worsened over a 5-year follow-up period. The Adolescent type 1 diabetes cardio-renal intervention trial (AdDIT) reported greater increases in cIMT from baseline to the 2–4-year follow-up in children with T1D who were in the highest quartile of albumin-creatinine ratio at baseline.⁴⁴ Another smaller study reported greater negative changes in brachial artery FMD from baseline to the follow-up (mean duration 3 years from baseline) in children with T1D (n=39; 51% female; mean age 11 years; mean disease duration 4 years) compared with children without T1D (n=45; age-matched).⁴⁵

There are no published data on the vascular health of children with T1D at the time of diagnosis and the progression of vascular damage during the initial years of the disease. A prospective cohort study will enable us to monitor changes in vascular complications from the time of diagnosis and characterise the progression of vascular damage during the early stages of post-T1D diagnosis.

Methods and analysis

Study Design and Objectives

This protocol is for a prospective longitudinal cohort study investigating vascular health in children through the first 2 years of T1D diagnosis living in Metro Vancouver, Canada. We hypothesise that damage to the vascular endothelium in children begins early in T1D and may be related to metabolic changes present at the time of diagnosis. The purpose of this study is to determine the extent of vascular damage in children in the first 2 years of T1D diagnosis and identify markers to mitigate early cardiovascular damage in these children.

The study will address the following three objectives in children through the first 2 years of T1D diagnosis: (1) to assess changes in arterial stiffness and 24 hours ambulatory blood pressure (24h-ABPM) and blood biomarkers of endothelial damage and glycaemic control; (2) to assess changes in body composition, surrogate markers of adiposity (Body Mass Index (BMI), waist circumference), and dietary intakes; and (3) to determine DNA methylation patterns in peripheral blood mononuclear cells and the relationship to arterial stiffness, BP, body composition and dietary intakes. We will also collect sociodemographic data and pubertal status (Tanner staging). Assessments will be performed at diagnosis (within 14 weeks of T1D diagnosis; baseline) and at 6, 12, 18 and 24 months post-diagnosis.

Participants

Participants between ages 8 and 18 years will be enrolled at the time of diagnosis (within 14 weeks). Children will be recruited starting March 2024 through the Endocrine and Diabetes Unit at BC Children’s Hospital (BCCH) in Vancouver, British Columbia, Canada.

All study visits will be conducted at time points that coincide with the routine clinical visits, baseline (within 14 weeks of T1D diagnosis), and at 6, 12, 18 and 24 months post-diagnosis; there will be a total of 5 visits. Each subject will undergo an interview, complete questionnaires, clinical assessment, blood collection and cardiovascular assessment.

Inclusion Criteria

1. Children between the ages of 8 and 18 years;

2. Within 14 weeks of T1D diagnosis;

3. Ability and willingness to undergo non-invasive arterial stiffness assessment and willingness to wear the 24-ABPM device.

Exclusion Criteria

1. Other cardiometabolic or endocrine disease diagnoses (type 2 diabetes; familial disorders of cholesterol metabolism; lupus);

2. Genetic syndromes (Down Syndrome; Prader-Willi);

3. Eating disorder diagnosis;

4. Transgender children taking hormone blockers or exogenous sex steroids;

5. Currently treated with medications known to affect metabolism (eg, glucocorticoids, antipsychotics).

Sample size calculation

The sample size of 75 subjects was calculated based on linear regression analysis with an effect size of 0.15, 80% statistical power, with three predictors, and a significance level of 0.01. We have chosen to recruit 150 subjects (75 males; 75 females) to account for attrition and missing data, which are expected to be approximately 15% based on our previous studies.

Recruitment

Potential participants will be identified at T1D diagnosis through the Endocrine and Diabetes Unit at BCCH and provided with a letter of initial contact describing the study. If the child and their parents/guardians are interested in the study, they will confirm with the Endocrine and Diabetes Unit and/or directly contact the research team. A member of the research team will then follow-up by phone, 1–2 weeks prior to their next clinic appointment, to determine whether the family is interested in participating. If so, the consent and assent forms will be emailed for review in advance of their clinic visit. Families will be told that they may contact the research assistant as often as needed to discuss the study protocol, in addition to the risks and benefits of participating.

If a family would like to participate in the study, they may book the study appointment in conjunction with their next clinic appointment via the research assistant. We have designed this recruitment protocol based on past experience with patients who have expressed the desire to coordinate testing with clinic visits to minimise visits to BCCH. Therefore, written consent and assent will be obtained on the day of the research/clinic appointment, following a review of the protocol, and providing another opportunity to address any questions or concerns the family may have. The family reserves the right to decline to participate in the study on arrival to the clinic, or at any time during study visits without any impact on their clinical care. Recruitment began in March 2024 and the anticipated completion date will be September 2027.

Study Procedure

On arrival at BCCH Research Institute, participants will be directed to the Clinical Research Evaluation Unit. Participants will be instructed to not smoke/vape, have caffeine (coffee, tea, soda, energy drink, chocolate), and to not eat a large meal (eg, eggs and bacon) 3 hours prior to the scheduled visit, as these may impact the assessments. A small snack (eg, fruits, crackers, nut butter, cheese, nuts, milk or yoghurt) and caffeine-free beverages are fine before the visit. Food intake will take into account the participant’s blood glucose levels and insulin dose/timing. We will take note of what was consumed prior to the visit and if a snack was consumed during the study visit.

All data collected by the research team will be de-identified to maintain participant confidentiality. Participants will be assigned a unique study number. The name, complete date of birth and personal health numbers of subjects will not be recorded on the data collection sheet. The principal investigators or designate will retain a separate master document with contact information for all participants. This document will be stored in paper format in a locked office at the BCCH Research Institute.

Participants will be asked to wear a swimsuit or t-shirt/tank top and sports shorts during the assessment as the brachial and femoral cuffs required for assessment of blood pressure and measures of arterial stiffness work best on bare skin. The first visit will take approximately 2 hours to complete, and the follow-up visits will be approximately 1.5 hours. The majority of clinic visits have returned to in-person and the children routinely have in-person clinic visits with their endocrinologist on at least a yearly basis. However, some of the children may choose to have virtual follow-up appointments (eg, at 6 and 18 months). In these instances, we will give the family the option of having us travel to their home with our mobile unit to collect the data and conduct the assessments (excluding the body composition analyses). A summary of the data collection is in table 1.

Table 1. Summary of data collection.

Time post-T1D diagnosis	Baseline*	6 months	12 months	18 months	24 months
Measures of vascular health
Pulse wave velocity	x	x	x	x	x
Augmentation Index	x	x	x	x	x
24h-ABPM	x		x		x
Clinic SBP and DBP	x	x	x	x	x
Blood sample for biomarkers	x		x		x
Clinical data
Body weight	x	x	x	x	x
Height	x	x	x	x	x
Waist circumference	x	x	x	x	x
Puberty status	x		x		x
Physical activity	x	x	x	x	x
Glycated haemoglobin (A1C)	x	x	x	x	x
Nutritional assessment	x		x		x
Body composition	x	x	x	x	x
Sociodemographic information
Age	x
Sex assigned at birth	x
Gender identity	x	x	x	x	x
Self-reported ethnicity	x
Family history of cardiovascular disease	x	x	x	x	x
Family history of diabetes	x	x	x	x	x
Smoking/substance use	x	x	x	x	x

^*Baseline measures will be taken at up to 14 weeks post-type 1 diabetes (T1D) diagnosis.

DBP, diastolic blood pressure; 24h-ABPM, 24 hours ambulatory blood pressure; SBP, systolic blood pressure.

Study outcomes

Primary outcomes

1. Change in pulse wave velocity during the first 24 months of T1D diagnosis. Carotid-femoral PWV will be measured with a SphygmoCor XCEL System (AtCor Medical Pty Ltd). Data will be collected at baseline (within 14 weeks of T1D diagnosis) and at 6, 12, 18 and 24 months post-diagnosis.

2. Change in clinic blood pressure during the first 24 months of T1D diagnosis. Systolic and diastolic blood pressure measures (average of 3 readings) will be collected using a Dinamap automated monitor (PRO 100–400, GE Medical Systems) and an appropriately sized cuff. Values will be standardised for age, sex and height using the 2017 American Academy of Pediatrics guidelines.⁴⁶ Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

3. Change in Augmentation Index during the first 24 months of T1D. Augmentation Index will be measured with a SphygmoCor XCEL System (AtCor Medical Pty Ltd). Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

4. Change in 24h-ABPM during the first 24 months of T1D diagnosis. Children will wear a 24h-ABMP (SpaceLabs) that measures blood pressure every 20 min for 24 hours. This will allow for any abnormalities not detected in the clinic to be identified (eg, masked hypertension). Data will be standardised and categorised according to the 2022 American Academy of Pediatrics guidelines.⁴⁷ Data will be collected at baseline and at 12 and 24 months post-diagnosis.

5. Change in biomarkers of vascular health during the first 24 months of T1D diagnosis. Blood biomarkers of vascular health will be assessed in plasma, serum and peripheral blood mononuclear cells (PBMCs). This includes: (a) E-selectin, intracellular adhesion molecule 1 (ICAM), vascular cellular adhesion molecule 1 (VCAM) and von Willebrand factor (vWF) will be quantified as circulating indicators of endothelial damage; (b) C-reactive protein (CRP), interleukin (IL)-6, IL-8, monocyte chemotactic protein-1 (MCP-1), isoprostane and tumour necrosis factor alpha (TNFα) will be quantified as indicators of inflammation; (c) creatinine and total homocysteine will be quantified as indicators of kidney function; (d) genome-wide DNA methylation patterns in PBMCs. Blood samples will be collected at baseline and at 12 and 24 months post-diagnosis.

Secondary outcomes

1. Sociodemographic information. Sociodemographic information will be collected including: age, sex and self-reported ethnicity will be collected at baseline. Gender identity and family medical history of cardiovascular disease and diabetes will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

2. Puberty status. Pubertal development (Tanner stage) will be evaluated by self-reported Tanner staging.^{48 49} The form used for the self-report development stage will be provided to participants according to their assigned sex at birth. Data will be collected at baseline and 12 and 24 months post-diagnosis.

3. Body weight. Body weight will be measured in children wearing light clothing, pockets emptied and without shoes using a balance scale. Weight will be recorded to the nearest 0.1 kg. Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

4. BMI. BMI will be calculated using weight and height measures [weight (kg)/height (m2)] and standardised for sex and age (z-score and percentile) according to WHO growth reference charts.⁵⁰ Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

5. Physical activity. Physical activity questionnaire will be administered to quantify relative levels of daily physical activity.⁵¹ There are two versions of the questionnaires: one for elementary school-aged children and the second for high school-aged children. Participants will be given a questionnaire that corresponds with whether they are in elementary school or high school. Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

6. Nutritional assessment. Three 24 hours dietary recalls will be used to assess dietary intakes. We will conduct three dietary recalls for three non-consecutive days. The first dietary recall will be conducted in person by a member of the research staff during the study visit. The other two diary recalls will be completed over the phone. During the in-person dietary recall, the participants and their parents/caregivers will be shown food models, plates, bowls, cups and spoons to help them better gauge the amounts of foods and beverages consumed. Data will be collected at baseline and at 12 and 24 months post-diagnosis.

7. Glycated haemoglobin (A1C). Blood A1C levels will be measured to assess glycaemic control over the past few months. This is routinely done at clinic visits; thus, we will obtain this information from the medical chart for each time point. Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

8. Body composition. Body composition will be assessed by dual-energy X-ray absorptiometry (DEXA) scan (Horizon Hologic Inc). The percent lean and fat mass and bone density will be calculated from the scans. Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

9. Height. Height will be measured in the children wearing no shoes. Height will be recorded to the nearest 0.1 cm with a stadiometer. Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

10. Waist circumference. Waist circumference will be assessed using a non-elastic flexible tape measure at the level of the umbilicus.⁵² The values will be standardised for sex and age (z-score) according to Sharma et al.⁵³ Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

11. Smoking and substance use. Smoking and substance use will be collected as self-reported through direct interview with the subject/family. Collecting this information will allow us to assess the potential impact of smoking habits on vascular health. In addition, tobacco, vaping, e-cigarette and cannabis use has been described to influence appetite and may affect dietary habits. Data will be collected at baseline and at 6, 12, 18 and 24 months post-diagnosis.

Biospecimens

Venous blood samples (20 mL) will be collected to evaluate biomarkers of vascular damage. Serum, plasma and PBMCs will be obtained from the blood samples.

With participant consent, we will store any remaining samples (serum, plasma, PBMCs, DNA) after completing our current analyses, in a biorepository. These samples will be used for future studies to identify new biomarkers of vascular damage and other complications; and/or biomarkers related to the pathophysiology of T1D in children.

Data management

Data collected from the participants will be stored on REDCap. Only authorised study team members will have access to enter and/or extract data from the database. Any paper will be stored in a locked filing cabinet inside a locked office at the BCCH Research Institute. Each participant and their corresponding data and blood samples will be assigned a random study number. No personal identifiers will be included in the data collection forms or storage tubes.

At the end of each study visit, individual results will be provided to the participant, including body weight, height, waist circumference, blood pressure, body fat percentage and bone mass density. With the participant and parent/guardian permission, abnormal blood pressure results that require medical consultation will be communicated to the primary care physician or specialist.

Patients and public involvement

Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.

Data analysis plan

Linear regression models will be used to assess changes in PWV and Augmentation Index at baseline (within 14 weeks of T1D diagnosis) with values at 6, 12, 18 and 24 months post-diagnoses and changes in 24h-ABPM mean, daytime and nighttime blood pressure and biomarkers of vascular damage at baseline with values at 12 and 24 months post-diagnosis. Models will be adjusted for appropriate covariates. Data from males and females will be analysed separately to understand the biological differences between sexes.

Ethics and dissemination

This research will be conducted according to the guidelines laid down in the Declaration of Helsinki, and all procedures involving human subjects were approved by the University of British Columbia Clinical Research Ethics Board and the Children’s and Women’s Health Centre of British Columbia Research Ethics Board (H21-03109). Written informed consent will be obtained from all parents or legal guardians and written assent, as appropriate by age, from children before participation.

ClinicalTrials.gov Identifier

NCT05790785.

Study findings will be disseminated to the scientific community through peer-reviewed manuscripts and presentations at conferences. After the study is completed, participants will receive a copy of the journal article, which will be accompanied by a summary in lay language such as an infographic.

Discussion

There are no published studies on vascular damage at T1D diagnosis and whether early prevention or reversal will improve outcomes. There is only one published intervention trial in children with T1D assessing cardiovascular outcomes. The large multicentre paediatric T1D trial (AdDIT)⁵⁴ compared treatment for 2.6 years with atorvastatin and/or quinapril (ACE inhibitor) in children that had T1D for at least 1 year before starting the trial and reported no effects on albumin to creatinine ratios (primary outcome) and minimal effects on BP and cIMT (secondary outcomes); other vascular measures were not assessed. Our longitudinal cohort study will fill this data gap and provide data and targets for future intervention trials. Our ultimate goal is to provide evidence to inform cardiovascular health monitoring from diagnosis as a standard component of clinical practice guidelines for children with T1D and to identify new approaches to prevent vascular damage in children with T1D.

There are some limitations to our study that must be considered. There is the potential that we may not observe BP abnormalities or arterial stiffness in the first 2 years of T1D diagnosis. This is unlikely based on our pilot study.³⁰ However, if this is the case, it will suggest little vascular damage is occurring within the first 2 years of T1D. This creates a window of opportunity to prevent future irreversible damage with the right treatment. We may not find a relationship between A1C at diagnosis and vascular damage at later time points. If this is the case, it will suggest that hyperglycaemia just prior to diagnosis has no detrimental vascular effects that manifest within the first 2 years of diagnosis. We recognise that A1C has limitations detecting past glycaemic control and does not indicate daily glucose excursions. Nonetheless, it is currently the best indicator of glycaemic control over the previous 2–3 months.⁵⁵ We further recognise that there will be differences in the extent of glycaemic monitoring by the children. Those with continuous glucose monitoring systems (CGMS) will have more accurate blood glucose data than those who self-monitor, but use of CGMS is limited by access, cost and feasibility. Once we have established our cohort, future studies will be designed to assess the effects of daily glucose excursions on cardiovascular health in children with CGMS.