| Objectives The aim of this paper is to estimate the prevalence of metabolic syndrome among adolescent students in China, and to explore the correlation of body mass index (BMI), waist-to-height ratio (WHtR) with metabolic syndrome.Methods The study population was a nationwide respective sample of 12 106 adolescents (boys 48.6% and girls 51.4%) from 9 cities in different provinces, who were 12-24 years old (mean 16.67±2.80). Anthropometric measure and blood pressure were measured by trained healthy technicians, and 7 738 fasting serum were collected after a 10-hour, overnight fast. BMI and WHtR were measured by weight, height and waist circumference. Fasting plasma glucose (FPG), triglycerides (TG) and high-density lipoprotein cholesterol (HDL) were measured with auto-analyzer. The metabolic syndrome was determined using the diagnostic criteria for children and adolescents which developed by international diabetes federation (IDF)The prevalence of metabolic syndrome was estimated overall, by sex, by region (urban or rural), by learning stage (middle, high school and college), by BMI and WHtR. BMI was estimated using the criteria for overweight and obesity developed by WGOC, and WHtR was estimated using the reference value of in Anhui adolescents. Prevalence values were compared using chi-squre tests. The Logistic regression was performed to determine whether measurements exceeding the BMI or WHtR cut points were predictive values of metabolic syndrome. Data were analyzed using statistical product and service solutions 13.0 (SPSS 13.0), and the significance level was set at 0.05.Results The overall prevalence of metabolic syndrome was 2.0% and had no significant difference in boys (1.9%) and girls (2.0%) (P>0.05). The prevalence of central obesity, elevated blood pressure, impaired FPG, higher TG and lower HDL which were individual components of the metabolic syndrome were 22.2%, 5.5%, 3.4%, 8.1% and 20.1%, respectively. It was more common to screen elevated blood pressure and impaired FPG in boys than in girls (P<0.05), but it was more common to screen central obesity and lower HDL in girls than in boys (P<0.05), the prevalence of higher TG in boys and girls had no significant difference (P> 0.05).The age-specific prevalence of metabolic syndrome did not decrease until 18 years old. The prevalence of central obesity was highest in 12-year-old age group (30.7%) and lowest in 21-year-old age group (14.3%). The prevalence of lower HDL increased from 12 to 16-year-old age group and then decreased. It showed that the prevalence of metabolic syndrome in college students was significantly lower than in middle school and high school students (χ~2=4.84,P=0.028). The incidences of central obesity, elevated blood pressure and impaired FPG in college students were significantly lower than in middle school and high school students as well (χ~2=47.53,P<0.001;χ~2=43.44,P<0.001;χ~2=21.23,P<0.001). The prevalence of lower HDL in high school students was higher than in middle school and college students (χ~2=115.86,P<0.001) but no significant difference existed for higher TG prevalence among the 3 groups.There were no significant difference between rural and urban students for metabolic syndrome and metabolic syndrome components. The prevalence of metabolic syndrome in west China was higher than in east and middle China ((χ~2=13.80,P<0.001). the prevalence of high blood pressure in middle China was the highest and central obesity was the lowest (χ~2=45.53,P<0.001;χ~2=24.21,P<0.001). The prevalence of impaired FPG in north China was the highest (χ~2=53.74,P<0.001), higher TG and lower HDL in west China was the highest.The overall prevalence of overweight and obesity were 7.8% and 3.2% of 8.9% and 3.9% in boys, 6.7% and 2.4% in girls. The total prevalence of overweight and obesity in boys was higher than in girls (χ~2=42.28, P<0.001).The prevalence of overweight and obesity were both kept a high level before 18-year-old age group, and the group of 22-year-old above had the lowest prevalence (3.5% and 0.4%). The total prevalence of overweight and obesity of college students was significantly higher than middle school and high school students (χ~2=104.52,P<0.001), and the east China was significantly higher than middle and west (χ~2=25.52,P<0.001;χ~2=51.84,P<0.001).The prevalence of metabolic syndrome in control, overweight and obesity group were 0.8%, 6.9% and 18.8%, respectively. The obesity group had the highest prevalence of metabolic syndrome components. Significant differences were existed among the 3 groups when ANOVA analysis was used. The obesity group had the significant highest level for all the indexes of metabolic syndrome components except HDL.The incidence with no metabolic syndrome components in Control, overweight and obesity group was 61.0%, 14.6% and 4.6%, respectively; the incidence with 1 metabolic syndrome component in the 3 groups was 30.9%, 48.3% and 42.6%, respectively; the incidence with 2 metabolic syndrome components in the 3 groups was 7.2%, 34.0% and 30.2%, respectively; the incidence with 3 metabolic syndrome components in the 3 groups was 0.7%, 6.8% and 14.9%, respectively; the incidence with 4 metabolic syndrome components in the 3 groups was 0.1%, 0.2% and 0.3%, respectively; but no one in the 3 groups had 5 metabolic syndrome components.The overall prevalence of higher WHtR was 7.4% and no significant difference in boys (7.5%) and girls (7.3%) (χ~2=0.24,P=0.621). The prevalence of higher WHtR was highest in 12-year-old age group and kept a high level in 12-14-year-old and 16-17-year-old age group. It also showed a higher prevalence of WHtR in college students than middle school and high school students (χ~2=57.86,P<0.001). The prevalence in middle China was much lower than east and west (χ~2=5.53,P=0.02;χ~2=12.90,P=0.00) and there was no significant difference between east and west China (χ~2=1.34,P=0.25). The prevalence of metabolic syndrome in control and higher WHtR group was 0.8% and 14.7% and it was more common to screen metabolic syndrome in higher WHtR group. There were significant differences between the 2 groups for the prevalence of central obesity, elevated blood pressure, higher TG and lower HDL.The incidence with no metabolic syndrome components in Control and higher WHtR group was 59.9% and 1.6%; the incidence with 1 metabolic syndrome component in the 2 groups was 31.8% and 43.8%; the incidence with 2 metabolic syndrome components in the 2 groups was 7.4% and 39.9%; the incidence with 3 metabolic syndrome components in the 2 groups was 0.7% and 12.7%; the incidence with 4 metabolic syndrome components in the 2 groups was 0.1% and 2.0%; but no one in the 2 groups had 5 metabolic syndrome components.By using multivariate logistic regression model, it showed that the odd risk to had metabolic syndrome in overweight and obesity groups were 3.91 and 6.86 times than control group. It also showed that the girls were inclined to have central obesity and lower HDL. The learning stage had a negative correlation to central obesity and impaired FPG (P<0.05).Conclusions The current epidemic situation of metabolic syndrome in Chinese students is just the"ice berg"; although the prevalence rate of metabolic syndrome among students is still relatively low, the population with 1-2 metabolic syndrome components is rather large which are the high risk individuals. At the same time, the risk of having metabolic syndrome among the students with normal weight and WHtR are high as well. After all, the control and prevention for metabolic syndrome is a rather severe challenge.The results also revealed that both obesity which assessed by BMI and high WHtR had a good correlation to metabolic syndrome, and WHtR had a good correlation to central obesity.
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