There are a number of diverse definitions of MS and many of these have been developed for adults. For instance, definitions have been provided by the WHO (Alberti and Zimmet, 1998); the National Cholesterol Education Program the Adult Treatment Panel III (NCEP III) (Expert panel, 2001) the European Group for the study of Insulin Resistance (EGIR); the American College of Endocrinology Task Force on the Insulin Resistance Syndrome (Garber et al., 2004) and the International Diabetes Federation (IDF) (Zimmet et al., 2005). However, still there is no consensus as to which definition is recommended to use in defining MS in adults.
However, using MS adult definitions is unsuitable and would underestimate the prevalence of MS in children and adolescents. Therefore, paediatric MS is defined by a number of different approaches. Some of these definitions have been modified from an adult definition such as those provided by Cook et al., (2003) and Weiss et al., (2004) modified from the NCEP III definition; but produce different cut-offs. However in 2007, the IDF released a new international definition of MS in paediatrics. They aimed to produce a useful and unified definition (Zimmet et al., 2007). Subsequently, there has been no consensus in using the IDF definition by researchers and there has been confusion regarding which definition of MS is most appropriate.
Table 1.3.1 summarises definitions of MS in the paediatric literature. So, the
prevalence of MS in the paediatric population has been broadly varied as a result of lack of an existing universal definition and lack of nationally representative samples. For example, a recent study was carried out on a small number of obese adolescents (n= 51) and those of normal-weight (n= 30) Danish adolescents aged 12 – 15 years (Gobel et al., 2012). They reported that the prevalence of MS amongst obese adolescents was 14% (7/51).
Table 1.3.1: Some studies on metabolic syndrome in paediatrics
References Sample size Place Age (years)
Metabolic syndrome definition Prevalence of metabolic syndrome
Globel et al., (2012) 51 (obese); M: 29, F: 22. 30 (normal weight);M: 13, F: 17
Denmark
12 - 15 years
IDF (having central obesity plus 2 or more criteria):
WC ≥ 90th FG ≥ 100 mg/dl TG≥ 150 mg/dl HDL-C ≤ 40 mg/dl DBP ≥ 130 or SBP ≥ 85 mmHg 14% of obese had MS
Non obese did not have MS
Al-Daghri et al.,
(2010) 1231; M: 760. F: 471Saudi Arabia
10 – 18 years
NCEP III modified by de Farranti et al. (3 or more of the criteria):
WC≥ 75th
TG≥ 100 mg/dl
HDL-C < 50 (Girls) and < 45 mg/dl (boys)
FG ≥ 110 mg/dl
BP> 90th
9.4% diagnosed with MS
Prevalence of MS was 10.3% and 8.1% in boys and girls; respectively
Taha et al., (2009) 57 (obese); M: 33. F: 24
Saudi Arabia
Mean (SD): 9.8 (3.5) years
NCEP III and WHO (3 or more criteria):
BMI > 95th
TG > 95th
HDL-C < 5th
SBP and DBP > 95th
FG > 110 mg/dl
29.7% of the sample met MS criteria
Eapen et al., (2010) 260 (obese); M: 153. F: 107
United Arab Emirate
Mean (SD): 14.5 (2.6) years
NCEP III modified by Cook et al. (3 or more of the criteria):
WC> 90th TG≥ 100 mg/dl HDL-C ≤ 40 mg/dl FG ≥ 110 mg/dl BP >90th 44% of obese had MS
Al-Isa et al., (2010) 431 (girls)
Kuwait 10 -19 years
IDF and NCEP III modified by Cook et al.
Discussed above By using IDF, 14.8% met MScriteria
9.1% had MS based on NCEP criteria
In addition, there is no consensus in definition of MS in paediatrics even in the same country or the same region. For instance two Saudi studies used different MS
definitions. Firstly, in a community-based cross-sectional study, Al-Daghri, (2010) examined (n=1231) for prevalence of MS. The overall prevalence of MS was found to be 9.4%. However, A hospital-based Saudi study was carried out on 57 children who were only obese with a mean age and standard deviation (SD) of 9.8 (3.5)(Taha et al., 2009). The prevalence of MS was found to be 29.7%. A review article by Tailor et al., (2010) found the prevalence of MS amongst children and adolescents around the world was around 10%, however, it varied from around 2% in those of normal weight up to around 32% in those defined as obese. Obese children and adolescents had an approximately 15-fold increased risk of having MS when compared to those defined as being normal weight (Tailor et al., 2010). Prevalence of obesity and MS was shown to be elevated in a parallel manner in the review by Tailor et al., (2010).
In addition, a United Arab Emirates study of 260 obese (defined as BMI > 95th
percentile) adolescents with a mean age (SD) of 14.5 years (2.6) (Eapen et al., 2010) reported one of the highest prevalence amongst adolescents in the world at 44% with MS. In a Kuwaiti study amongst the female adolescent population aged 10 - 19 years old (Al-Isa et al., 2010) prevalence of MS was 14.8% and 9.1% according to IDF and NCEP III; respectively.
To sum up, the previous studies defined MS by using different approaches with hugely different sample sizes and types of samples; consequently, there are
apparently enormous differences in MS prevalence even in same population. Reinehr et al., (2007) aimed to compare the prevalence of MS according to the criteria of Weiss, Viner, De Ferranti, Cook, WHO, European Group for the study of Insulin Resistance (EGIR), NCEP III and the IDF. This study was carried out on 1205 German, Caucasian overweight children between 4 and 16 years of age defined in line using IOTF criteria (Cole et al., 2000). They observed that the prevalence of MS varied significantly (p value < 0.001) (6 – 39 %) in these definitions and only 9% of participants conformed to all of the MS definitions. Also, some of MS definitions such
as IDF and NCEP definitions use age-adjusted indicator criteria which are important to classify MS according to a specific age because prevalence of MS is more likely to occur in adolescents than younger children.
Even though the majority of studies that defined MS in paediatrics included the following variables: anthropometrics, blood pressure, plasma glucose and lipid profile, there were substantial differences in defining abnormal values of individual MS components. For example, the cut-off level for TG and HDL-C are fixed with more than 150 mg/dl less than 40 mg/dl; respectively, by IDF definition. The NCEP III modified by de Ferranti et al., 2004 on the other hand used for TG more than 100mg/dl and less than 50 mg/dl for girls and 45 mg/dl for boys.
The recent existence of a standard MS definition helps answering to what extent MS affects children and adolescents, facilitates international comparisons of prevalence, assists in conducts and interpretation of clinical trials, helps in investigate the
underlying pathological mechanisms and facilitates health professionals to identify and manage MS.