Waist-to-height ratio and metabolic profile in children and adolescents of the city of SALTA
SUSANA GOTTHELF, PATRICIA RIVAS.
Centro Nacional de Investigaciones Nutricionales. Administración Nacional de Laboratorios e Institutos de Salud. ANLIS. Salta.
(4400) Salta, Argentina E-mail
Recibido 17-ENE-2019 – ACEPTADO después de Revisión el 04-MARZO-2019 There are no conflicts of interest to disclose.
The waist to height ratio (WHtR) is a simple anthropometric measurement, easy to measure, stable during growth, related to cardiometabolic markers in childhood and adolescence. Values higher than 0.50 correlate with the increase in cardiovascular risk. Objective: to evaluate the association between the waist-to-height ratio and metabolic profile in children and adolescents of the city of Salta (2014). Methods: cross-sectional study, secondary database (Nutritional Survey of Salta, 2014). Two-stage stratified sample. Variables: sex, age, waist-to-height ratio: cut-off point 0.50. Cut-off values of the Consensus of dyslipidemias in Pediatrics (PAS 2015): CHOL ≥200 mg/dl; LDL-C ≥130 mg/dl; HDL-C <35 mg/dL TG ≥100 mg/dl in children up to 9 years, ≥130 mg/dl from 10 to 19 years. Glycemia ≥100 mg/dl. Analysis: frequency distribution (Chi2, Fisher), Kolgomorov (normality). Comparison of mean values U Mann-Whitney, p <0.05. SPSS V18. Results: 189 children were evaluated (mean: 5.6 years) and 197 adolescents (mean: 14 years). Women represented 49.5%. Mean WHtR in children and adolescents were 0.49 and 0.46. The prevalence of WHtR ≥0.50 was 45% in children and 21.8% in adolescents. Children and adolescents with WHtR ≥0.50 had lower mean HDL values (43.47/42.12 mg/dl), and higher LDL (98.15/98.56 mg /dl) and TG values (110.4/133.49 mg/dl) (p<0.05). In children and adolescents with WHtR ≥0.50, the frequency of low HDL and elevated TG was significantly higher. Conclusions: WHtR should be included in the routine evaluation of children and adolescents. WHtR ≥0.50 should undergo an additional cardiometabolic risk assessment, since the component of abdominal obesity plus HDL and altered TG are part of the Metabolic Syndrome
Obesity is a chronic, complex and multifactorial disease, that may start during childhood and/or adolescence, and is determined by an imbalance between food ingestion and energy expenditure. Prevalence in children and adolescents increased alarmingly in recent years, accompanied by many co-morbidities that have been described in adults; among them a mixture of cardiovascular risk factors such as hypertension, hyperglycemia, and dyslipidemias, associated particularly to fat deposits in the abdomen .
Overweight and obesity are positively associated to cardiovascular disease (CVD), the main cause of death in the world. Elevated levels of LDL cholesterol, triglycerides, and reduced HDL-C are considered significant risk factors for onset atherosclerosis in children/adolescents, associating the high percentage of abdominal fat to unfavorable lipid profiles.
The meeting of World Health Organization (WHO) experts on the topic of obesity, acknowledged the need to have indicators to supplement body mass index (BMI) measurement, which would allow to identify individuals with morbidity risk increase, related to abdominal fat accumulation .
BMI and abdominal circumference (AC) are simple and affordable screening measures to predict obesity and metabolic disease, and are commonly used in adults and children . Using BMI is frequent in clinical assessment; however, it presents a limitation in the determination of body fat distribution. By definition, it cannot differentiate fat mass from fat-free mass; therefore, an elevated BMI may not necessarily reflect more adiposity . This index is not necessarily the most appropriate one to discriminate metabolic risk, or at least it should be supplemented by the determination of another indicator that would provide information on visceral fat mass distribution. The implementation of other specific anthropometric indices to evaluate the pattern of abdominal fat, constitutes an alternative to detect patients in risk .
Waist-to-height ratio has been proposed as an anthropometric index, easy to measure, to detect central obesity early and to evaluate the associations between variables of cardiometabolic risk factors and central or intra-abdominal obesity . It is a relatively constant anthropometric index of abdominal obesity through different ages, gender or racial groups, and it not only detects central obesity and adverse cardiovascular risk in overweight/obese children, but also in children with normal weight. The findings in different populations have supported the premise that waist-to-height ratio is a simple and efficient anthropometric index, proving a close relationship between morbidity and mortality .
Aim: To evaluate the association between WHtR and metabolic profile in children and adolescents in the city of Salta (2014).
Secondary database. Data were extracted from the Encuesta Nutricional de Capitales del NOA (Argentinian North-West Capitals Nutrition Survey), Salta chapter (2014), conducted by the Centro Nacional de Investigaciones Nutricionales - CNIN (National Center of Nutrition Investigations). Cross-sectional, stratified, two-stage study (census block groups/tracts and homes).
Population: There were 189 children (2-9 y/o) and 197 adolescents (10-19 y/o) of both genders, belonging to 197 homes from the city of Salta, between April and June, 2014.
Variables: Gender (female/male), age (children/adolescents age groups). WHtR: cut-off point 0.50 normal/≥0.50 increased. Metabolic profile: glycemia, LDL cholesterol, HDL cholesterol, triglycerides.
Abdominal circumference (AC): Technique: flexible, inextensible tape measure graded in millimeters. The patient standing, arms relaxed at the sides of the body, measurement at the middle point between the costal margin and the iliac crest, during exhalation .
Body length: Height was measured standing, with a steel tape measure graded in cm and mm, supported on a flat and firm vertical surface (wall), placing the tape measure’s zero on the floor, in a horizontal plane. Patients were measured with no shoes or objects on their head (Frankfurt plane position), after performing a deep inhalation and contacting with it a mobile top, the measurement was recorded in cm and mm.
The measurement techniques were conducted by anthropometrist nurses, properly standardized according to guidelines by the Sociedad Argentina de Pediatría - SAP .
Biochemical parameters: Cutoff values from the Consensus on the management of Dyslipidemias in Pediatrics (SAP 2015)  were considered: Total cholesterol (CHOL) ≥200 mg/dl; LDL cholesterol (LDL) ≥130 mg/dl; HDL cholesterol (HDL) <40 mg/dl; triglycerides (TG) ≥100 mg/dl in children up to 9 years, ≥130 mg/dl from 10 to 19 years. Basal glycemia (BG) >100 mg/dl.
Measurements were made from peripheral blood samples by automated colorimetric and enzymatic analysis, under internal and external (PEEC, Programa de Evaluación Externa de Calidad [External Quality Evaluation Program] by the Fundación Bioquímica Argentina) quality control.
Exclusion criteria: Those who did not meet the indicated fasting hours, absence of consent/agreement by adults, parents/tutors and/or adolescents.
Statistical analysis: Frequency distribution (Chi2, Fisher), Kolgomorov (normality), comparison of mean values by Mann-Whitney U test. P<0.05. Statistical programs: SPSS 18 EXCEL.
Ethical considerations: The participants signed an informed consent/agreement before the origin study (Argentinian North-West Capitals Nutrition Survey) and adhered to the current guidelines according to the Helsinki declaration
There were 189 children (mean age 5.56 years) and 197 adolescents (13.94 years) evaluated. Women were 49.48% of the sample. Tables 1 and 2: Prevalence of increased WHtR was 45% in children and 21.8% in adolescents. Hypertriglyceridemia and low HDL were the most prevalent alterations of the lipid profile, in both age groups. No significant differences were found in frequencies according to gender.
Table 1. Waist-to-height ratio and metabolic profile according to gender in children of the city of salta.cnin
Frequencies: Chi2; Fisher; p<0.05
Table 2. Waist-to-height ratio and metabolic profile according to gender in adolescents of the city of salta.cnin.
Frequencies: Chi2; Fisher; p<0.05
Table 3: The mean WHtR value was 0.49 for children and 0.46 for adolescents (p=0.000).
Table 3. Mean whtr values and metabolic profile in children and adolescents of the city of salta.cnin.
MANN WHITNEY U TEST, p<0.05.
Table 4: Both in children and in adolescents, mean TG and LDL values were significantly higher in those with WHtR ≥0.50. With respect to HDL, mean values were significantly less in both groups.
Table 4. Mean values of metabolic profile according to whtr in children and adolescents of the city of salta.cnin.
ANN WHITNEY U TEST, p<0.05.
Figures 1 and 2: Altered TG and HDL prevalences were significantly greater in children and adolescents with WHtR ≥0.50.
DISCUSSION The results of this investigation show a high elevated WHtR prevalence in children and adolescents in the city of Salta, which is associated to a metabolic risk profile, represented by higher frequency of abnormal levels of cardiometabolic risk factors.
There is relevant information about the implication of visceral fat in the development of metabolic complications. Waist measurements are efficient to determine central fat distribution, acting as strong markers of cardiometabolic risk in the pediatric population. Using WHtR has the advantage of not requiring conversion to z scores or percentiles. It has been suggested that a cutoff point of 0.50 would be easier to understand by patients and families, thus creating a potential for a significant public health message, “maintaining waist circumference at half the height” . It not only detects central obesity and adverse cardiometabolic risk in children with overweight/obesity, but also in children with normal weight, and it identifies those that do not present such risk conditions, which has repercussions on pediatric primary care practice.
WHtR presents advantages over BMI to identify metabolic risk associated to obesity in children and adolescents. It considers height, BMI, and combines them with abdominal adiposity distribution, which is particularly pathogenic through the development of inflammatory mediators associated to obesity . Central adiposity acts as a complex, highly active endocrine organ, which results in a variety of hormones and cytokines (tumor necrosis factor alpha, interleukin-6, etc.) that would participate in hemodynamic processes deregulation in the body through different mechanisms; among them, hepatic lipogenesis and insulin resistance, free fatty acids release by adipocytes, macrophage infiltration in adipose tissue, modifications in the renin-angiotensin-aldosterone system, and sympathetic nervous system activation .
In recent years, several studies report the use of WHtR in childhood and adolescence, emphasizing that not only obese individuals may present an increased WHtR, but also children with normal weight and with overweight; from there the importance of a periodical measurement and timely referral [11-12]. Studies in Japanese students from 9 to 11 years of age and Brazilian students from 7 to 10 years of age, showed that WHtR had a good performance, comparable to BMI and waist circumference (WC) to identify abdominal adiposity excess and total body fat, respectively for age [11,12]. BMI and WHtR showed a similar capacity to identify US children  and adolescents with cardiovascular risk factors (HEALTHY study) . In children from 6 to 10 years from Brazil, Kuba et al, concluded that WHtR presents advantages such as its simplicity, although it may not be superior to BMI to discriminate metabolic risk in children and adolescents .
We cannot leave out studies that found dissimilar results as presented by Sánchez Oliveira, who reports a greater correspondence between BMI and WC with skinfold measurements than with WHtR . The study by Sijtsma et al, who investigated the performance of the same indicators to predict cardiometabolic risk in children from 3 to 7 years, WHtR showed the lowest correlation scores with variables that indicated cardiometabolic risk .
The disparities in literature could be related to the age group of the evaluated individuals and differences between populations.
In this study, WHtR prevalence ≥0.50 was 45% in children and 21.8% in adolescents (no significant differences according to gender), with mean values of 0.49 in children and 0.46 in adolescents. In adolescents in school, Gotthelf et al, in the same city of Salta in 2008, surveyed a prevalence of WHtR ≥0.50 of 14.5% in females and 11.6% in males, showing an increase in the frequency of the indicator .
Comparatively, in Mexican children in school age, WHtR ≥0.50 was observed in 39% of the population studied, with predominance in children of 8 to 9, and 10 to 12 years of age, and of male gender (58.6%) . Arnaiz et al, surveyed in students from Santiago de Chile of 6 to 14 years of age, a WHtR >0.55 prevalence of 15% and 22.2% between 0.50 and 0.55 . In Venezuelan adolescents, the frequency of abdominal obesity (WHtR ≥0.50) was 18.8% with no significant differences between genders, with a mean value of 0.45 for males and 0.46 for females ; while Ribeiro et al, reported a mean WHtR of 0.45 in Brazilian adolescents, with no differences by gender . Finally, a recent work made in Norwegian children in school age (6-12 years), surveyed a prevalence of WHtR ≥0.50 of 14%, concluding that it could be a proper indicator to identify abdominal obesity in children .
The analysis of mean values in the lipid profile of children and adolescents of this sample, showed significantly higher values of TG and LDL and lower values of HDL when WHtR exceeded the cutoff value of 0.50.
The study by Ruiz N. et al, in Venezuelan adolescents also showed significantly higher values of total cholesterol, TG, CHOL/HDL ratio, insulinemia, HOMA score and less HDL concentration in those presenting abdominal obesity (WHtR ≥0.50) . Khoury, in his investigation, observed the absence of Metabolic Syndrome in children and adolescents with normal weight and overweight, with WHtR <0.50; while it was present in those with increased BMI and with WHtR between 0.50 <0.60 (10%), this percentage is tripled when the ratio was equal or greater than 0.60. He concludes that cardiometabolic risk is increased as central adiposity increases, measured by WHtR .
In regard to WHtR with the prevalence of hyperglycemia or high mean values, the results of this study did not find such association, which could be due to the low prevalence found. However, other studies reported that WHtR ≥0.50 is clearly sensitive to detect hyperglycemia in children and adolescents [19-24].
Between the limitations of this study, the fact stands out that it is not possible to establish causality relationships, but association relationships instead, as this is a cross-sectional study; and the capacity to estimate the risk of presenting the evaluated alterations is limited.
From this study, we can draw the conclusion that WHtR presents an association with metabolic profile in children and adolescents from Salta. Its use is recommended in routine clinical evaluation, thus facilitating the selection of patients that should undergo a metabolic risk test, as the abdominal obesity component plus altered HDL and TG constitute part of the Metabolic Syndrome.
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