Prevalence of metabolic syndrome and its risk factors in Canadian children and adolescents: Canadian Health Measures Survey Cycle 1 (2007-2009) and Cycle 2 (2009-2011) - HPCDP: Volume 36-2, February 2016

Volume 36 · Number 2 · February 2016

Prevalence of metabolic syndrome and its risk factors in Canadian children and adolescents: Canadian Health Measures Survey Cycle 1 (2007-2009) and Cycle 2 (2009-2011)

M. MacPherson, MBAFootnote i Footnote ii ; M. de Groh, PhDFootnote i ; L. Loukine, MScFootnote iii ; D. Prud'homme, MDFootnote iv Footnote v ; L. Dubois, PhDFootnote vi 

https://doi.org/10.24095/hpcdp.36.2.03

This article has been peer reviewed.

Author references:

Correspondence: Miranda MacPherson, Social Determinants and Science Integration Directorate, Public Health Agency of Canada, 916B-785 Carling Avenue, Ottawa, ON K1A 0K9; Tel: 613-668-4018; Fax: 613-960-0921; Email: miranda.macpherson@phac-aspc.gc.ca

Abstract

Introduction: We investigated the prevalence of metabolic syndrome (MetS) and its risk factors, and the influence of socioeconomic status, in Canadian children and adolescents.

Methods: Canadian Health Measures Survey cycle 1 (2007-2009) and cycle 2 (2009-2011) respondents aged 10 to 18 years who provided fasting blood samples were included (n = 1228). The International Diabetes Federation (IDF) consensus definition for children and adolescents (10-15 years) and worldwide adult definition (≥ 16 years) were used to diagnose MetS. Prevalence of MetS and its risk factors were calculated and differences by socioeconomic status were examined using x2 tests.

Results: The prevalence of MetS was 2.1%. One-third (37.7%) of participants had at least one risk factor, with the most prevalent being abdominal obesity (21.6%), low HDL-C (19.1%) and elevated triglyceride levels (7.9%). This combination of abdominal obesity, low HDL-C and elevated triglyceride levels accounted for 61.5% of MetS cases. Participants from households with the highest income adequacy and educational attainment levels had the lowest prevalence of one or more MetS risk factors, abdominal obesity and low HDL-C.

Conclusion: The prevalence of MetS (2.1%) was lower than previously reported in Canada (3.5%) and the USA (4.2%­-9.2%), potentially due to the strict application of the IDF criteria for studying MetS. One-third of Canadian children and adolescents have at least one risk factor for MetS. Given that the risk for MetS increases with age, these prevalence estimates, coupled with a national obesity prevalence of almost 10% among youth, point to a growing risk of MetS and other chronic diseases for Canadian youth.

Keywords: Canadian Health Measures Survey, metabolic syndrome, health surveys, cardiometabolic risk factors, prevalence, adolescent, child

Key findings

  • Having metabolic syndrome (MetS) increases the risk for chronic disease—cardiovascular disease by two and type 2 diabetes by five.
  • Only 2.1% of Canadian youth have MetS. However, one-third of Canadian youth have one or more risk factors for MetS.
  • The biggest risk factor for MetS is abdominal obesity. As more youth are becoming obese, MetS will probably increase among Canadian youth.
  • Risk of MetS increases with age. As a result, the risk for chronic diseases will probably increase as the Canadian population ages.
  • Youth who live in better off or better educated households have the lowest risk for MetS.

Introduction

Chronic diseases constitute the leading cause of preventable death in Canada and the world as well as the largest avoidable burden on the public health care system.Footnote 1 The metabolic syndrome (MetS) is a constellation of cardiometabolic risk factors that are predictive for chronic disease and all-cause mortality.Footnote 2,Footnote 3,Footnote 4 It is estimated that risk of cardiovascular disease (CVD) doubles and the risk of type 2 diabetes increases fivefold if MetS is present.Footnote 3,Footnote 4,Footnote 5,Footnote 6

MetS is characterized by the presence of different combinations of risk factors including obesity, hypertension, elevated fasting triglycerides, insulin resistance, low total cholesterol, high low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol (HDL-C), elevated apolipoprotein B, elevated C-reactive protein and elevated homocysteine.Footnote 7 Footnote 8 Footnote 9 These clinical features of MetS, if present together, tend to suggest a common etiology; the proposed mechanisms underlying MetS and its influence on health outcomes are discussed elsewhere.Footnote 7 Footnote 10 Footnote 11 

The global prevalence of obesity and diabetes has increased dramatically in the past quarter century.Footnote 12 This increase, in turn, has contributed to a higher prevalence of MetS.Footnote 13 Worldwide estimates of the prevalence of MetS range from 1.2% to 22.6% for youth and 9.0% to 35.0% for adults, depending on the definition of MetS used, the region, the study design, the years of the study, and the age group and study population.Footnote 13,Footnote 14,Footnote 15,Footnote 16 In Canada, the prevalence of MetS among adults is between about 11.4% and 22.2%, which is greater than the prevalence estimates of 10% to 15% measured in adults in the early 1990s.Footnote 17,Footnote 18,Footnote 19,Footnote 20,Footnote 21,Footnote 22 In comparison, the prevalence of MetS among adults in the USA is between about 22% and 34%.Footnote 23,Footnote 24,Footnote 25,Footnote 26 It is widely accepted that the prevalence of MetS increases significantly with age.Footnote 17,Footnote 18,Footnote 19,Footnote 20,Footnote 23 The national prevalence among youth aged 12 to 19 years is 3.5% in Canada (based on a 2012 study using the Adult Treatment Panel III criteria for MetS) and 4.2% to 9.2% in the USA, with about 42% to 63% of youth in the USA having one or more MetS risk factors.Footnote 19,Footnote 27,Footnote 28,Footnote 29 Further examination of national prevalence among youth will help us understand the progression of MetS and its risk factors among Canadians.

There is substantial evidence supporting an inverse relationship between socioeconomic status (SES) and CVDs, conditions that share some risk factors with MetS.Footnote 30,Footnote 31,Footnote 32 Studies examining the relationship between SES and MetS reveal a similar pattern in which people with a lower social status experience a significantly higher prevalence of MetS.Footnote 17,Footnote 19,Footnote 20,Footnote 33,Footnote 34 Canadian national studies have shown that the prevalence of MetS is significantly lower among people from households with postsecondary education compared to those with less education, a relationship that is particularly evident in women.Footnote 17,Footnote 19,Footnote 20 This inverse relationship remains consistent between household income and MetS, albeit less pronounced, with Canadian households with the lowest quartiles of income having a higher prevalence of MetS than households with average and higher incomes.Footnote 17,Footnote 20

A challenge in determining the prevalence of MetS has been the use of multiple criteria and definitions for identifying this condition. In response, the International Diabetes Federation (IDF) released the IDF Consensus Worldwide Definition of the Metabolic Syndrome as a single, universally accepted tool.Footnote 35 The IDF defines MetS as the presence of abdominal obesity (measured by waist circumference) and 2 or more of the following risk factors: low levels of HDL-C, hypertension, elevated fasting triglyceride levels and elevated glucose concentration.Footnote 6,Footnote 36 Before the IDF consensus definition, the most recognized definitions were criteria established by the World Health Organization, the European Group for the Study of Insulin Resistance, and the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III criteria) (NCEP ATP III).Footnote 9,Footnote 37,Footnote 38

Diagnosing MetS among children and adolescents proves particularly challenging given the difficulty in establishing accurate, meaningful and harmonized criteria for this population. Consequently, prevalence estimates of MetS among children and youth vary greatly depending on the adopted definition.Footnote 8 In 2007, the IDF released their Consensus Definition of the Metabolic Syndrome in Children and Adolescents.Footnote 36 This criterion provides an age- and sex-specific definition for youth aged 10 to 15 years. The IDF definition further stipulates that the worldwide adult definition of MetS should be applied for individuals aged 16 years or older and that MetS should not be diagnosed in children less than 10 years old.Footnote 36

The main objectives of this study were to investigate the prevalence of MetS and its risk factors, and the influence of SES on these risk factors, in Canadian children and adolescents (10-18 years) using nationally representative data from the Canadian Health Measures Survey (CHMS). This study builds upon an earlier national analysis of Canadian youth

  • by including those aged 10 and 11 years;
  • by calculating the prevalence of one or more risk factors for MetS among youth;
  • by examining the patterns of risk presentation; and
  • by using data from two cycles of the CHMS.Footnote 19

This is the first national study to strictly apply the IDF consensus definition of MetS in children and adolescents, the most current and universally accepted definition of MetS for youth; and to use Canadian age- and sex-specific waist circumference reference data to determine abdominal obesity in Canadian children and youth.

Methods

Data source

The CHMS is a nationally representative survey designed to collect information on the health of Canadians.Footnote 39,Footnote 40,Footnote 41 Conducted by Statistics Canada, the CHMS consists of an in-home interview and a physical assessment conducted at a mobile examination centre. The interview collects demographic, socioeconomic, family history and general health information. The physical assessment includes measures of anthropometry, spirometry, blood pressure, fitness and oral health and involves collecting biological specimens.Footnote 39,Footnote 40,Footnote 41 The survey covered Canadians living at home in the 10 provinces and 3 territories, although people living on reserves and other Aboriginal settlements, in institutions and in certain remote regions as well as full-time members of the Canadian Forces were excluded.Footnote 39,Footnote 40,Footnote 41 The CHMS cycle 1 (2007-2009) collected data on people aged 6 to 79 years, with cycle 2 (2009-2011) expanding to cover those aged 3 to 79 years.Footnote 39,Footnote 40,Footnote 41 In total, this represents 96.3% of the Canadian population.Footnote 39,Footnote 40,Footnote 41

The CHMS produces reliable estimates at the national level by age group and sex through a multistage sampling strategy.Footnote 40 Footnote 40 Footnote 41 Footnote 42  The selection of collection sites was informed by the Labour Force Survey sampling frame. A multitude of practices were used to minimize non-response; the combined response rate for home and clinic visits was 51.7% for cycle 1 and 55.5% for cycle 2.Footnote 39 Footnote 40 Footnote 41 Footnote 42  Statistics Canada calculated the sampling weights by multiplying the selection weights for collection sites by the selection weights for dwellings, followed by a series of adjustments for non-response at the initial, interview and MEC stage.Footnote 42  

Study population

All 10- to 18-year-old CHMS respondents who provided fasting blood samples for cycle 1 (2007-2009) or cycle 2 (2009-2011) were included (n = 1228). No participants were pregnant. Sample weights specific to the fasting subgroup were provided by Statistics Canada to ensure appropriate representativeness at the population level.

Criteria for diagnosing MetS

We applied the IDF consensus definition of MetS for children and adolescents to participants aged 10 to 15 years and the IDF worldwide adult definition adult criteria to participants aged 16 to 18 years.

The IDF consensus definition for children and adolescents defines MetS as having abdominal obesity (waist circumference equal or greater than the 90th percentile by age and sex) and the presence of two or more of the following clinical features: elevated triglycerides (≥ 1.7 mmol/L); low HDL-C (< 1.03 mmol/L); high blood pressure (systolic ≥ 130 mm Hg and/or diastolic ≥ 85 mm Hg and/or diagnosis of hypertension); and elevated glucose (≥ 5.6 mmol/L and/or diagnosis of type 2 diabetes).Footnote 36 

The IDF worldwide adult criteria define MetS as having abdominal obesity and the presence of two or more of the following clinical features: high triglycerides (≥ 1.7 mmol/L), low HDL-C (< 1.03 mmol/L in males and < 1.29 mmol/L in females); high blood pressure (systolic ≥ 130 mm Hg and/or diastolic ≥ 85 mm Hg and/or diagnosis of hypertension); and high glucose (≥ 5.6 mmol/L and/or diagnosis of type 2 diabetes).Footnote 35 

We defined abdominal obesity using the 90th percentiles from the age- and sex-specific waist circumference reference data established from the 1981 Canadian Fitness Survey.Footnote 43 We applied the waist circumference cut-offs for 11-year-olds to those aged 10 to 11 years since this reference provided estimates for those aged 11 to 18 years only.

Variables for assessing demographic and socioeconomic status

A respondent's demographic and SES was assessed through the variables of household educational attainment, household income adequacy, Aboriginal status, and immigrant status. The use of household education and household income variables in this study is consistent with previous studies examining the relationship between SES and MetS.Footnote 17,Footnote 19,Footnote 20,Footnote 26 Education is the most frequently used indicator of SES in epidemiological studies and, among indicators of SES, it tends to have the strongest and most consistent relationship with cardiovascular health.Footnote 20,Footnote 31,Footnote 44 Household income is another well-established SES indicator and determinant of health.Footnote 44,Footnote 45,Footnote 46,Footnote 47,Footnote 48 Statistics Canada calculated income adequacy by classifying each participant into categories based on total household income from all sources and the number of people living in the household.Footnote 39,Footnote 40

To allow for greater statistical power, we re-classified both the household educational attainment and income adequacy variables from 4 categories into 3. For income adequacy, we combined the "lowest income" and "lower middle income" categories, resulting in "lowest and lower middle," "upper middle" and "highest" categories. For household educational attainment, we combined the "less than secondary school graduation" and "secondary school graduation" categories, resulting in "secondary school graduation or less," "some postsecondary" and "postsecondary graduation" categories.

Statistical analysis

We conducted statistical analyses using SAS version 9.3 (SAS Institute Inc., Cary, NC, US) for data manipulation and variance estimation using the bootstrap method.Footnote 49 The prevalence of MetS and each risk factor were estimated and expressed as a frequency and a percentage with a 95% confidence interval (CI). x2 tests were used to examine differences in MetS, and each risk factor by gender, Aboriginal status, immigrant status, household education and income adequacy. The analyses were conducted using weighting and bootstrapping. Statistical significance was set at a p value of less than .05.

We obtained ethics approval for this project from the University of Ottawa's Research Ethics Board.

Results

Description of study sample

To be able to evaluate the criteria for MetS, of the original sample of child and adolescent respondents aged 10 to 18 years, we included in our study only those participants who provided fasting blood samples. This resulted in a final sample of 1228 participants. The sample included slightly more males (51.5%) than females (48.5%).

Table 1 shows an overview of the sample by demographic and SES.

 

Table 1 Sample profile, 10–18 yearsFootnote 1.1

Characteristics Study sample, n Percentage of study
sample, %
Demographic profile (n = 1228)
Sex
Male
632 51.5
Female
596 48.5
Age, years
10
172 14.0
11
184 15.0
12
127 10.3
13
151 12.3
14
115 9.4
15
117 9.5
16
131 10.7
17
121 9.8
18
110 9.0
Socioeconomic profile
Income adequacy (n = 1178)
Lowest and lower middle
247 19.7
Upper middle
333 25.8
Highest
598 50.4
Household education (n = 1193)
Secondary school graduation or less
126 11.0
Some postsecondary
81 6.4
Postsecondary graduation
986 78.3
Aboriginal origin or identity (n = 1227)
Aboriginal
46 4.4
Not Aboriginal
1181 95.5
Immigrant status
Immigrant
120 10.2
Not immigrant
1108 89.8

Prevalence of MetS

Only 25 study participants were diagnosed with MetS, which represents 2.1% of participants (95% CI: 0.8-3.3)Footnote *  (Table 2). This small number of participants with MetS prevented accurate disaggregation by sex, age or SES.

 

Table 2 Prevalence of metabolic syndrome and risk factorsFootnote 2.1, 10–18 yearsFootnote 2.1 (n = 1228)

Condition Total Sample Male Female p value
Frequency,
n
% (95% CI)
CV
Frequency % (95% CI)
CV
Frequency % (95% CI)
CV
Abbreviations: BP, blood pressure; CV, coefficient of variation; HDL-C, high-density lipoprotein cholesterol. Note: Blank cells (—) indicate that the results cannot be published because of a cell size n < 10 and/or a CV ≥ 0.3306. The prevalence of elevated BP was too low to provide an accurate statistical estimate.
MetS 25 2.1 (0.8-3.3)
0.29Footnote 2.2
Number of risk factors
≥ 2
123 10.8 (7.4-14.2)
0.15
71 6.1 (3.5-8.7)
0.02
52 4.7 (2.8-6.5)
0.19
.3658
≥ 1
420 37.7 (33.8-41.6)
0.05
212 18.1 (15.4-20.8)
0.07
208 19.6 (16.4-22.9)
0.08
.3179
Abdominal obesity 240 21.6 (16.6-26.7)
0.11
130 10.6 (7.3-13.9)
0.15
110 11.0 (7.5-14.5)
0.16Footnote 2.2
.7443
Low HDL-C 218 19.1 (16.6-21.8)
0.06
107 8.8 (6.6-11.0)
0.12
111 10.54 (8.4-12.3)
0.09
.2863
Elevated triglycerides 82 7.9 (4.8-11.0)
0.19Footnote 2.2
42 4.7 (2.2-7.3)
0.26Footnote 2.2
40 3.2 (1.7-7.2)
0.22Footnote 2.2
Elevated glucose 22 1.7 (0.7-2.8)
0.30Footnote 2.2

Prevalence of individual risk factors

Over one-third (37.7%; 95% CI: 33.8-41.6) of children and adolescents had at least one of the clinical features of MetS (1 or more risk factors) (Table 2). Risk factors in order of prevalence were abdominal obesity (21.6%; 95% CI: 16.6-26.7), low HDL-C (19.1%; 95% CI: 16.6-21.8), elevated triglycerides (7.9%; 95% CI: 4.8-11.0) and elevated glucose (1.7%; 95% CI: 0.7-2.8)Footnote ** . The prevalence of elevated blood pressure was too low to provide an accurate statistical estimate. There were no gender differences for the prevalence of each risk factor.

Pattern of risk factor combinations

The most prevalent single risk factors were abdominal obesity (10.7%), low HDL-C (9.8%) and elevated triglycerides (2.7%) (Table 3). The most prevalent distinct combinations of two risk factors were abdominal obesity coupled with low HDL-C (5.1%) and abdominal obesity and elevated triglycerides (1.5%). Among distinct combinations of three risk factors, the most prevalent combination was abdominal obesity, low HDL-C and elevated triglycerides (1.3%). This combination of three risk factors accounted for 61.5% of MetS cases (Table 3).

 

Table 3
Pattern of metabolic syndrome risk factor combinationsFootnote 3.1


Risk factor combination (n = 1228) Frequency (%)
Presence of 1 risk factor
Abdominal obesity
131 (10.7)
Low HDL-C
121 (9.8)
Elevated TG
33 (2.7)
Presence of 2 risk factors
Abdominal obesity + low HDL-C
63 (5.1)
Abdominal obesity + elevated TG
19 (1.5)
Presence of 3 risk factors
Abdominal obesity + low HDL-C + elevated TG
16 (1.3)
Risk factor combination in participants with MetS (n = 26) Frequency (%)
Abbreviations: HDL-C, high-density lipoprotein cholesterol; TG, triglycerides. Note: Risk factor combinations with cell sizes n < 10 were not published as prevalence were too low to provide accurate statistical estimates. 
Presence of 3 risk factors
Abdominal obesity + low HDL-C + elevated TG
16 (61.5)

Associations between SES (household educational attainment and income adequacy) and risk factors

Participants from families with the highest incomes had the lowest percentage of one or more risk factor(s) (35.5%; 95% CI: 29.8-41.2), abdominal obesity (18.4%; 95% CI: 11.7-25.1) and low HDL-C (17.5%; 95% CI: 14.2-20.6) versus those from families with the lowest and lower middle incomes (Table 4). Educational attainment results showed that participants with a household member with postsecondary graduation had the lowest percentage of one or more risk factor(s) (35.3%; 95% CI: 31.0-39.6), abdominal obesity (19.8%; 95% CI: 14.6-25.0) and low HDL-C (17.5%; 95% CI: 14.8-20.2) versus those from households with some postsecondary education or secondary school graduation or less. Due to small cell sizes, the results could not be disaggregated by Aboriginal or immigrant status.

 

Table 4 Relationship between metabolic syndrome risk factors and socioeconomic status, fasting sub-sample ages 10–18 yearsFootnote 4.1

Condition Presence of ≥ 1 risk
factor(s)
Abdominal obesity Low HDL-C
% (95% CI)
CV
% (95% CI)
CV
% (95% CI)
CV
Abbreviations: BP, blood pressure; HDL-C, high-density lipoprotein cholesterol; SES, socioeconomic status. Note: Small cell sizes prohibited further analysis of BP, glucose and triglyceride risk factors and Aboriginal and immigrant status SES factors. 
Income Adequacy (50 missing)
Lowest and lower middle 35.9 (25.9-46.0)
0.14
21.4 (11.8-30.9)
0.22Footnote 4.2
19.4 (12.7-26.1)
0.17Footnote 4.2
Upper middle 41.8 (34.4-49.3)
0.09
28.1 (19.7-36.6)
0.15
20.2 (15.2-25.2)
0.12
Highest 35.5 (29.8-41.2)
0.08
18.4 (11.7-25.1)
0.17Footnote 4.2
17.5 (14.2-20.6)
0.09
Household education (35 missing)
Secondary school graduation or less 43.7 (29.4-58.0)
0.16
31.8 (17.6-46.1)
0.22Footnote 4.2
19.3 (6.9-31.7)
0.31Footnote 4.2
Some postsecondary 42.8 (32.4-53.2)
0.12
28.3 (13.7-42.9)
0.25Footnote 4.2
26.1 (15.1-37.3)
0.21Footnote 4.2
Postsecondary graduation 35.3 (31.0-39.6)
0.06
19.8 (14.6-25.0)
0.13
17.5 (14.8-20.2)
0.08

Discussion

The prevalence for MetS among children and adolescents (2.1%) was lower than previously reported in Canada (3.5%) and the USA (4.2%-9.2%).Footnote 19,Footnote 27,Footnote 28,Footnote 29 Assuming our sample is representative of the Canadian population, this prevalence of 2.1% would be equivalent to about 64 832 children and adolescents. The prevalence of one or more risk factors (37.7%) among children and adolescents was also lower than reported in the USA (42%-63%).Footnote 28 In comparison to earlier national estimates on Canadian youth, our study's lower prevalence may be attributed to our applying the IDF definition of MetS, which has slightly more stringent criteria, including the required presence of abdominal obesity.Footnote 19,Footnote 43,Footnote 50,Footnote 51 Furthermore, MetS is known to increase with age and our sample included younger ages (10­-11 years) and had greater numbers of younger participants (n = 356 for 10-11 years) than older, adolescent participants (n = 231 for 17-18 years).Footnote 17,Footnote 23

The lower prevalence estimates we found compared to those in the USA may be attributable to several factors. Obese youth have a higher prevalence of MetS than do those of normal weight and the prevalence of obesity among youth is higher in the USA than in Canada.Footnote 52,Footnote 53,Footnote 54 The prevalence estimates in the USA were calculated using data from the National Health and Nutrition Examination Survey with variation in the periods of data collection (ranging from 1988-2006), the MetS definition (all variations of ATP III) and criteria for abdominal obesity. Our study followed a strict application of the IDF MetS definition including age- and sex-specific cut-offs. Finally, our study does not include Canadian residents living on reserve or in other Aboriginal settlements, populations shown to have a higher prevalence of MetS.Footnote 55,Footnote 56,Footnote 57

Despite the overall low prevalence of MetS, note that one-third (37.7%) of study participants had at least one risk factor for MetS. This finding, coupled with a prevalence of obesity of almost 10% among Canadian children and youth, is disconcerting as the probability of MetS also increases with obesity.Footnote 26 Further, given that age is one of the most significant predictors for MetS, it is reasonable to assume that children and adolescents with one or more risk factors are more susceptible to MetS and, correspondingly, chronic disease as adults.Footnote 2,Footnote 3,Footnote 4 Evidence indicates that, in the long term, adults with MetS have an elevated risk of CVD-attributed mortality, although a moderate-to-high level of cardiorespiratory fitness has been shown to mitigate some of this risk.Footnote 53,Footnote 58

Our findings support the conclusions of previous studies that abdominal obesity, low HDL-C and elevated triglycerides are the most prevalent risk factors of MetS among children and adolescents;Footnote 28  in fact, this combination accounted for 61.5% of all MetS cases in this study. The most prevalent risk factor was abdominal obesity (21.6%), which may be attributed to over one-quarter of Canadian youth being overweight or obese.Footnote 59  The IDF considers abdominal obesity as a prerequisite for MetS given that it is associated with an increased risk of cardiovascular disease and an independent predictor of insulin resistance, lipid levels and high blood pressure.Footnote 35 Footnote 36 Footnote 60 Our study defined abdominal obesity using age- and sex-specific reference data established from the 1981 Canadian Fitness Survey (90th percentile).Footnote 43 Domestic prevalence estimates of obesity among youth have almost doubled in the past 25 years, meaning that these predefined cut-offs represent norms for the Canadian population before this dramatic increase in body fat.Footnote 59 Footnote 61 

Consistent with previous studies on youth, hypertension is not highly prevalent in the early onset of this syndrome.Footnote 28

Participants from families in the highest income adequacy and household educational attainment groups had the lowest prevalence of one or more risk factors, abdominal obesity and low HDL-C, which is consistent with earlier findings between SES and MetS risk factors.Footnote 17,Footnote 19,Footnote 20,Footnote 62 For abdominal obesity, a dose-response relationship was present for household education. The relationship between household education and prevalence of risk factors appeared to be more sensitive than household income, which is also consistent with previous findings.Footnote 17,Footnote 20,Footnote 62 This may be attributed to the influence of education on health literacy and behaviour, such as nutrition and physical activity, which are related to abdominal obesity and MetS.Footnote 22,Footnote 63 Further, household education is considered to be more stable, and less influenced by health status, than household income over the life course.Footnote 30 More broadly, participants from households with lower education and income levels are more likely to experience unfavourable social, physical and economic environments that can contribute to poorer health outcomes, including a higher rate of mortality attributed to CVDs.Footnote 30,Footnote 47 These results point to a need for interventions, including public policy, public education, research and medical care, that focus on mitigating the impact of lower levels of education and income on health outcomes. Research focussed on elucidating the causal pathways through which SES influences the risk for MetS and CVDs throughout the life course would be useful in designing effective, targeted interventions.

Future studies using more cycles of CHMS data may have the statistical power with which to examine MetS and its risk factors in Canadian children and adolescents in greater detail. The sex differences in MetS in relation to SES should be examined to better understand the sex-specific ways in which unfavourable socioeconomic conditions affect MetS outcomes. Further, regression analyses are needed to comprehensively examine the relationship between MetS, its risk factors, behaviour such as physical activity and sleep, and SES.

Strengths

This is the first national study to apply the IDF consensus definition of MetS to children and adolescents and to use Canadian age- and sex-specific waist circumference reference data for determining abdominal obesity to Canadian children and youth. Strictly applying the IDF criteria for studying MetS at the population level in Canada will allow for more accurate comparisons with future studies on MetS in children and adolescents.

This study was conducted using government survey data that is both high quality and representative of 96% of Canadians.

Limitations

Descriptive statistics was the only method we could use to examine MetS using this dataset of Canadian children and adolescents because the sample size was small; only those participants from whom fasting blood samples were taken were included. The sample size and low prevalence of MetS did not allow for an analysis of the relationship between each risk factor and MetS. The small sample size also prohibited a robust statistical analysis of the influence of demographic and SES variables on MetS and allowed only limited analysis of the influence of these variables on risk factors with no distinction by sex. It was not feasible to disaggregate by sex, age, Aboriginal status or immigrant status. Furthermore, the cross-sectional design of the CHMS limits inference about causal pathways underlying the observed relationships. Consequently, the study focussed on the prevalence of each MetS risk factor.

Nonetheless, the study results improve the understanding of the current landscape of cardiometabolic risks among Canadian children.

Conclusions

By investigating the prevalence of MetS and its risk factors among Canadian children and adolescents, this study highlights important health and socioeconomic considerations for Canada's child and adolescent population. The results affirm previous findings of a low prevalence of MetS among youth. The results also highlight important indicators of future health risk among Canadian youth by showing that one in three have at least one risk factor for MetS, one in five have abdominal obesity, and one in five have low HDL-C. Efforts to prevent, diagnose and treat MetS and its risk factors among youth are important to prevent type 2 diabetes, cardiovascular diseases and premature mortality.

Acknowledgements

We are grateful to Statistics Canada for conducting the Canadian Health Measures Survey and to the people of Canada who participated in the study.

There were no competing interests.

We acknowledge the support of the University of Ottawa's Department of Epidemiology and Community Medicine and the Public Health Agency of Canada.

References

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