The metabolic syndrome is an important health issue in children and adolescents with regard to the long term implications of cardiovascular morbidity and type 2 diabetes. This is one of a few reports to examine the frequency and factors associated with the metabolic syndrome among childhood cancer survivors in Korea. The results of this study showed that the frequency of the metabolic syndrome in childhood cancer survivors was 19.4%. This is about twice the frequency in the general population of children according to a study conducted by the Korean national health and nutrition survey10)
Several studies have reported an increased prevalence of overweight or obese childhood cancer survivors1
. The reported prevalence of overweight or obese childhood cancer survivors has varied from 16 to 50%5
. In this study, 17.3% were overweight or obese, which is consistent with previous studies. This is a higher frequency compared to the prevalence in the general Korean population, which has recently been reported to be around 10%6)
. Moreover, our results show that BMI SDS was positively associated with prevalence of metabolic syndrome. Therefore, continuous surveillance of BMI in childhood cancer survivor is crucial for early detection of metabolic syndrome in these patients.
The basic feature of the metabolic syndrome is central obesity. An appropriate definition of central obesity for children and adolescents is challenging. Central obesity was found in 13.2% of the patients reported here, which is consistent with previous studies15)
. In this study, the BMI and waist circumference percentiles were correlated with the cranial irradiation dose, which could have caused hypothalamic/pituitary damage that manifested as hormonal problems. Growth hormone has been implicated not only in linear growth, but also in metabolism. The results of this study showed that the percent body fat of patients with GHD tended to be higher than in patients without GHD.
The amount of fat and lean body mass, and the distribution of fat are important risk factors for the prediction of cardiovascular disease and type 2 diabetes16
. Unfortunately, there is no Korean reference data for body composition in this age group. Therefore, the reported reference data of percent body fat was used12
. Higgins et al.19)
reported that an upper cut-off point of 33% body fat is an indicator of cardiovascular disease risk in children. In this study, 41.2% (26/63) of the patients had a percent fat that was above 33%, despite a median BMI SDS of 0.14 (-0.71 to 0.9). This may suggest that the body composition of childhood cancer survivors should be considered even if they are not overweight or obese.
About half of the patients in this study had at least one abnormal lipid profile. The percent body fat was positively correlated with the triglyceride and negatively correlated with the HDL-C. Vatanparast et al.20)
reported that DXA-derived fat mass indices can be used for predicting blood lipid profiles in postmenopausal women. Although studies in children are lacking, our findings suggest the importance of the percent fat in predicting the lipid profile.
In childhood cancer survivors, the frequency of the metabolic syndrome appears to be increased. This finding was associated with BMI SDS, presence of GHD, and cranial irradiation. The notable fact was that the body composition of childhood cancer survivors was metabolically unfavorable even if they were not obese. Therefore, childhood cancer survivors should have thorough metabolic evaluation including measurement of the percent body fat even if their BMI is in the normal range. Furthermore, more intense surveillance and education is necessary for the patients who had cranial irradiation and GHD.
The major limitations of this study are as follows: a cross-sectional setting, small sample size from a single center and lack of optimal comparison group. Thereafter, a prospective long-term cohort study is needed to reproduce the results of this study.
In Korea, the number of childhood cancer survivors increased to approximately 20,000 to 25,00021)
. However, there are no large cohort studies in Korea like The Childhood Cancer Survivor Study of USA or British Childhood Cancer Survivor Study of United Kingdom. In 2008, Children's Oncology Group published the update of Long-Term Follow-up Guidelines for Survivors of Childhood, Adolescent, and Young Adult Cancers22)
for screening and management of late effects resulting from therapeutic exposures during the treatment of malignancies. The guideline recommends annual physical examination of height, weight, BMI, blood pressure for screening metabolic syndrome. Moreover, laboratory tests including fasting blood glucose, insulin, and lipid profile are recommended every 2 years if the patient is overweight or every 5 years if the patient is in normal weight22)
. Now, we need the Korean cancer survivor cohort and follow-up guidelines. The primary preventive interventions for the patients with risk factors of metabolic syndrome include education of the patients and parents about the diet modification and adequate physical activities for maintaining normal BMI and body fat percent.
In conclusion, a better understanding of the determinants of the metabolic syndrome during adolescence might provide insights into preventive interventions for improving health outcomes and reducing the incidence of cardiovascular disease in adults.