Correlation of neck circumference with abdominal circumference and body mass index in patients with metabolic syndrome in a hospital from northern Peru: a cross-sectional study


 Background

We aimed to evaluate the correlation of neck circumference with abdominal circumference and body mass index in patients with metabolic syndrome in Chocope, Trujillo.
Methods

This cross-sectional study included patients with untreated metabolic syndrome. Health professionals measured the anthropometric parameters of participants as per the international guidelines. Pearson’s correlation coefficients and single and multiple regression models were used for analysis.
Results

Data from 250 participants showed homogeneous distribution with respect to age, comorbidities, and biochemical properties according to sex. The mean age was 53.6 years. A positive correlation of neck circumference with abdominal circumference (r = 0.6 and 0.74 for females and males, respectively) and body mass index (r = 0.51 and 0.65 for females and males, respectively) was observed. The linear correlation model showed that a 1-cm increase in neck circumference increased the abdominal circumference by 2.20 cm (p < 0.001) and 2.27 cm (p < 0.001) and body mass index by 0.72 kg/m2 (p < 0.001) and 0.94 kg/m2 (p < 0.001) in males and females, respectively, independent of other variables.
Conclusions

In participants with metabolic syndrome in this study, neck circumference showed a strong correlation with abdominal circumference and body mass index. This anthropometric parameter can be extremely useful for evaluating obesity among patients with metabolic syndrome.

disease, cirrhosis, abdominal tumors, and other health conditions that interfere with neck and abdominal circumference measurements were excluded.
With the 250 participants enrolled in the primary study, the power of the study was estimated considering an expected correlation coe cient (r) of 0.5 ± 0.1 between neck circumference and abdominal circumference (11) and a 95% con dence interval. Accordingly, the study power was estimated to be 98%. The primary study employed a systematic random sampling method to enroll the initial number of estimated patients from the outpatient clinic of the internal medicine department.

Data collection
The primary study involved conducting interviews with health personnel. The survey, which was designed based on the RENATA-1 survey (12), included measurements of social, demographic, and anthropometric parameters (weight, height, abdominal circumference, and neck circumference) as well as levels of blood pressure, glucose, high-density lipoprotein (HDL), and triglycerides (TG). The RENATA-1 survey uses the Latin American Diabetes Association's criteria with the following cutoff points: abdominal obesity of >94 and >88 cm for men and women, respectively, and neck obesity of ≥41 and ≥35 cm for men and women, respectively.
Blood samples were collected after 8 h of fasting to measure the levels of TG, glycemia, and HDL. Anthropometric parameters were measured in an upright position with patients in light clothing. Weight, height, abdominal circumference, and blood pressure were measured following the WHO guidelines (12). Weight was measured using a digital scale calibrated with an error of 0.1 kg. Neck circumference was measured using a tape with an accuracy of 1 mm, starting from the lower margin of the laryngeal prominence below the thyroid cartilage, which is perpendicular to the axial axis, with the participant's head following the horizontal Frankfurt's plane (13). Abdominal circumference was measured using a tape with an accuracy of 1 mm, starting from the midpoint between the lowest rib and the iliac crest on the midaxillary line.

Variables
The outcomes of interest in this study were BMI (kg/m 2 ) and blood pressure (mmHg), with neck circumference (cm) being the main independent variable. All parameters were measured during the same interview by the same interviewer.

Statistical analysis
Age, BMI, and neck circumference are presented as means and standard deviations, whereas categorical variables are reported as frequencies and percentages. Pearson's correlation coe cients were estimated to determine differences between subgroups of interest. Simple linear regression models using the Gaussian distribution family and the identity link function were employed to evaluate the association of neck circumference with abdominal circumference and BMI. The nal multiple linear regression model was adjusted for age, hypertension, hypertriglyceridemia, and hyperglycemia and strati ed according to sex; 95% con dence intervals (95% CI) were estimated and signi cant pvalues of <0.05 were reported. The dataset was initially exported in Microsoft Excel 2010® and analyzed using STATA v.14.0 (College Station, TX: StataCorp LLC).

Ethics
The primary study was approved by the Institutional Review Board of the Hospital II-1 Chocope and the School of Human Medicine from the Universidad Nacional Pedro Ruiz Gallo. The primary study followed ethical principles by minimizing risks when obtaining blood samples from participants and protecting their physical and mental well-being. Similarly, in our secondary data analysis, study participants were anonymized by removing any personal information that could identify them.

Results
Among the 250 participants included in this study, 67.6% were women; 85.2%, 46.0%, and 43.6% had high blood pressure, hyperglycemia, and obesity, respectively. Their average age was 53.6 years, and both males and females had similar BMI. However, there were differences in neck and abdominal circumferences according to sex. Accordingly, men had slightly higher values of mean anthropometric parameter measurements than women. However, women had a higher prevalence of disorders related to blood pressure, abdominal circumference, and neck circumference than men (Table 1). Moreover, neck circumference was correlated with abdominal circumference and BMI in both men and women (p < 0.001) ( Figure 1). However, other variables, such as age, arterial hypertension, hypertriglyceridemia, and hyperglycemia, were not correlated with abdominal circumference or BMI in either sex (Table 2).  (Table 3). Our study evaluated patients with untreated metabolic syndrome; previous studies did not specify this criterion. This could explain why our study showed higher correlation coe cients because individuals with metabolic syndrome gain weight, BMI, and abdominal circumference over time, which could have resulted in an increased correlation among anthropometric parameters by the time these patients presented with an illness (15).
To the best of our knowledge, no study has yet evaluated patients with untreated metabolic syndrome. However, there is evidence in patients with other metabolic diseases (16,17). For example, a recent study in patients with pre-diabetes reported a positive linear correlation between neck circumference and abdominal circumference (16). Moreover, another study reported a signi cant correlation between both variables in patients with type 2 diabetes (17). Despite the presence of metabolic disorders, the association between both parameters has been consistently reported.
Neck circumference is an anthropometric parameter that measures the distribution of subcutaneous fat in the upper body, thereby helping predict metabolic risk (8, 18). Several studies have supported the association between neck circumference and components of the metabolic syndrome, including abdominal circumference and BMI. A recent systematic review that addressed the association of neck circumference with cardiometabolic markers reported a signi cant association between neck circumference and abdominal circumference, fasting glycemia, the homeostatic model assessment of insulin resistance, and lipid pro le (19).
Previous studies have consistently found that neck circumference is positively correlated with abdominal circumference, BMI, and other cardiovascular markers, such as the lipid risk pro le, suggesting that neck circumference is a prognostic factor for mortality in patients with a high cardiovascular risk (6, 8, 19). Dai et. al. studied adults with two or more risk factors for cardiovascular disease and reported that an increased neck circumference was associated with a higher incidence of cardiovascular events and mortality (8).
Our study found that the correlation of neck circumference with abdominal circumference and BMI was higher in men than in women. The nding, however, is not homogeneous across studies worldwide. Several studies comparing the correlation between neck circumference and abdominal circumference according to sex have demonstrated higher coe cients in women than in men (11,16), whereas others have shown otherwise (7,14). Women tend to accumulate more subcutaneous fat, whereas men accumulate more visceral fat (20); this could justify a more robust association in males. However, in patients diagnosed with metabolic syndrome, sex may not play a key role in other factors. The current study found that women had a greater prevalence of hypertension and hyperglycemia, both of which are metabolic risk factors. Consequently, when analyzing the association between neck circumference and abdominal circumference after controlling for these parameters, women showed a greater decrease in the β coe cient than men.