Neck Circumference as A Screening Tool to Predict Obesity: A Cross Sectional Study in Coastal Karnataka, India

Background : BMI is commonly used to classify obesity in adults. WC and WHR are considered as acceptable measures of obesity. However in community settings these can be a time-consuming method. Instead, Neck circumference (NC) can be used to screen for obesity. Methodology : A cross sectional study among 310 study participants in rural field practice area of Karwar Medical College. Data was collected using pre designed semi structured questionnaire and anthropometric measurements as per standard guidelines. Pearson’s correlation coefficient was used to assess correlation. NC cut off values were obtained from ROC. Results : In our study, the correlation of NC with BMI was highly correlated among both males(r=0.529), and females (r=0.565). Kappa statistics depicted moderate agreement with BMI males (κ = 0.512); females (κ = 0.496) and NC. The cut-off values obtained for NC using ROC curve for males (35.5cm) and females (31.5cm) were statically significant associated in comparison to BMI to determine obesity in both males (χ2 = 58.57, and females (χ2 = 21.54). Conclusion: This study


INTRODUCTION
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health. More than 1 billion people (close to 650 million adults) worldwide are obese and this number is increasing in an alarming rate. 1 Obesity is a disease of public health importance impacting most body systems. It leads to a range of noncommunicable diseases (NCDs), such as type 2 diabetes, cardiovascular disease, hypertension and stroke, various forms of cancer, as well as mental health issues. People with obesity are also three times more likely to be hospitalized for COVID- 19. 1 As per the NFHS-5 data, the prevalence of overweight/obesity among men and women has doubled in the last two decades from 1998-99 to 2019-21 in India. 2 The prevalence of overweight or obesity among man and women in rural areas of Karnataka is 25.0% and 25.6% respectively. 2 Body mass index (BMI) is commonly used to classify overweight and obesity in adults. Others measurements such as waist circumference (WC), waist-tohip ratio (WHR), and body fat percentage are considered as acceptable measures of adult body fat mass and obesity. However, in community settings these can be a time-consuming method. Instead, Neck circumference (NC) can be used to screen for overweight and obesity. Since it is low cost and easy to measure, may be well-accepted in the community settings.
In this study, we aimed to study NC as a screening tool to predict obesity and its correlation with other anthropometric measurements in rural area of coastal Karnataka.

METHODOLOGY
This was a community based cross sectional study conducted from January 2022 to March 2022. Sample size was calculated using the formula n = Zα/2 2 pq /e 2 where 'p' was the percentage of overweight or obesity. According to NFHS-5 Karnataka state fact sheet data, the prevalence of overweight or obesity among man and women in rural areas is 25.0% and 25.6% respectively. 2 standard normal deviate (Zα/2) at 5% i.e., 1.96 and allowable error (e) of 10% was considered and the sample size hence calculated was 310.
The study was conducted in Chendia-rural field practice area of community medicine of department, karwar institute of medical sciences in coastal Karnataka. Institutional ethical committee permission was taken before the start of the study. The rural field practice area Chendia is located on either side of national highway 63 with houses being divided in 6 areas and each area was equally represented in total sample size. In each area a landmark location like a school or temple was selected and from there a direction was randomly chosen for that day for selecting the houses. The first house was randomly selected and then the remaining houses were selected on alternate basis on either side of the road till the target of that day was met. When the interviewers visited the house, all individuals in that family aged 18 years and above were assessed for eligibility. Individuals who had history of thyroid disorders and those who refused to be part of the study were excluded. As per clinical neck examination method 3 individuals' neck was examined by interviewers for any thyroid enlargement and those who had thyroid enlargement were also excluded. Individuals who fitted to our inclusion criteria were explained the objectives of study. They were interviewed after obtaining written informed consent. This method was followed till our total sample size was met. Data regarding socio demographic characteristics and reported comorbidities was collected in a semistructured questionnaire from the study participants. Physical examination was done and measurements such as height, weight, hip, waist and neck circumference were measured using standardized methods.

Anthropometric measurements
i) Weight: weight of the individual was measured without any footwear and minimal clothing to the nearest 0.1 kilogram using a standard portable weighing machine and the scale was zeroed before each session. 4 ii) Height: height of the individual was measured in the standing position without any footwear, standing on the flat surface against wall, with weight evenly distributed on both feet, heel together, and the head positioned so that line of vision will be perpendicular to the body. Height was recorded in centimetre to the nearest 0.5 cm. 4 iii) Waist circumference: Individual stands with arms at the sides, feet positioned close together and weight evenly distributed across the feet. Waist circumference was measured at the approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest. It was measured at the end of a normal expiration. 5 iv) Hip circumference: Individual stands with arms at the sides, feet positioned close together and weight evenly distributed across the feet. Hip circumference was measured around the widest portion of the buttocks. 5 v) Neck circumference (NC): Neck circumference was measured in the midway of the neck, between mid-cervical spine and mid-anterior neck, to within 1 mm, with measuring tape calibrated. In men with a laryngeal prominence (Adam's apple), it was measured just below the laryngeal prominence.
All circumferences were taken with tape snug around the body, but not pulled tight that it was constricting. Non-stretchable tape was used to take all measurements.
Definitions and classifications a) Waist circumference-Waist circumference of more than 90 cm in male and 80 cm in females is the cut off for abdominal obesity. 5 b) Waist Hip Ratio (WHR) = Waist circumference (cm) ÷ Hip circumference (cm) WHR more than 0.9 will be considered abnormal for males and more than 0.85 will be considered to be abnormal for females. 5 c) Body Mass Index (BMI)=Weight(kg)/Height (m) 2 Body Mass Index was considered as the standard for defining obesity and overweight. Modified BMI classification for Asian population was used. BMI of 18.5-22.99 kg/m 2 was considered normal. BMI of 23-24.99 kg/m2 was categorized as overweight and BMI more than or equal to 25kg/ m 2 was defined as obese. 6 Analysis: Data was entered, cleaned, coded and analyzed using Epi-info 7.2 version software. Results were expressed in frequencies and proportions with 95% confidence interval. Statistical tests like Pearson's correlation coefficient were used to assess correlation. Neck circumference cut off values were obtained from Receiver Operating Characteristic (ROC) curve.

RESULTS
Out of 310 study participants, 223 were males and 87 were females. Majority of them were in the age group of 21 to 40 years. Mean age of male participants was 37.6 ± 14.8 years and for females 43.7 ±16.3 years. In the present study mean BMI for males was 23.16 ± 3.97 and for females 24.1 ± 4.7, mean waist circumference for males was 85.61 ± 9.98cms and for females 86.99 ± 11.45cms, mean waist-hip ratio (WHR) for males was 0.90 ± 0.05 and for females 0.9 ± 0.06 and mean neck circumference for males was 35.92 ± 3.89cms and for females 32.23 ± 3.04cms.

DISCUSSION
Obesity once considered a problem only in highincome countries, is now dramatically on the rise in low-and middle-income countries, particularly in urban settings. It is a major risk factors for a number of chronic diseases, including cardiovascular diseases such as heart disease and stroke, which are the leading causes of death worldwide. 7 BMI is generally considered as standard to classify overweight and obesity in adults. WHR, WC and percentage of body fat are also accepted indicators of body fat mass. However, BMI is not perfect because it is only dependant on height and weight and measuring these in community settings can be time consum-ing and also it has to be calculated which again is a drawback. 8 But in a country like India, it can be particularly challenging to measure these parameters precisely, as per the standardized methods among women due to cultural inhibitions. Many studies have suggested that NC can be an independent correlate of metabolic risk factors. 9-12 NC can be a simpler tool which can be used to screen for overweight and obesity. Since it is low cost and easy to measure, it may be well-accepted in the community settings also. Our study has shown a strong association between NC and BMI for males and female study participants.
Upper body obesity is associated with insulin resistance, hypertriglyceridemia, diabetes and furthermore increases the risk for metabolic complications. 13 Preis SR et al. 14 examined the association between neck circumference and cardiometabolic risk factors among participants in the Framingham Heart Study. The study demonstrated that neck circumference, as a proxy of upper-body subcutaneous fat, is a novel, discrete, and pathogenic fat depot both independent of and synergistic with visceral adipose tissue (VAT). It concluded that Neck circumference is associated with CVD risk factors even after adjustment for VAT and BMI.
In the present study, an attempt was made to find the neck circumference cut-offs for males and females which can be used as an alternate to BMI. In our study, 310 participants were involved, mean age of male participants was 37.6 ± 14.8 years and for females 43.7 ±16.3 years. The anthropometric measurements like BMI, waist circumference, WHR, neck circumference observed in this study were similar to finds by Sanjana SN et al. 15 neck circumference: a valid anthropometric tool, Dudeja V et al. 16 body fat and BMI in Asian Indians, Patnaik, et al. 17 neck and waist circumference as anthropometric measures of overweight/obesity.
In our study we found that correlation between neck circumference with WHR, BMI and waist circumference was weak, moderate and highly correlated in males, whereas they were weak and highly correlated in females. In a cross-sectional study by Sunil Kumar et al. 18 in 2009, carried out among 300 patients admitted in a rural hospital in Wardha, in both men and women, BMI correlated positively with NC (Corr. Coeff = 0.59, p < 0.01) and weight (Corr. Coeff = 0.60, p <0.01); NC (Corr. Coeff = 0.74, p < 0.01) and weight (Corr. Coeff = 0.82, p < 0.01), respectively. NC ≥ 38 cm for men and ≥ 34.7 cm for women were the best cut-off points for determining subjects with overweight.
More recently, in 2019, Sanjana SN et al. 15 conducted a study among urban slum population in Davangere consisting of 512 study participants and concluded that males with NC ≥36 cm and females with NC ≥ 29 cm are to be considered obese. In a study conducted in Maharashtra by Patil C et al. 19 with 479 study subjects in 2013, it was observed that the cut off of 36.50cms in males and 32.50cms in females will help to screen the population of Asian Indian origin.

CONCLUSION
Neck circumference may be used as a simple and less time-consuming screening tool to identify individu-als who are overweight and obese. This study concluded that men with NC ≥ 35.5 cm and females with NC ≥ 31.5 cm are to be considered obese. The sensitivity of this screening test for this cut off was 79.83% and 82.4% in males and females respectively.

LIMITATION OF THE STUDY
Since our study was conducted in a small geographical area community-based study, results may overestimate the true correlation between NC and obesity. Another limitation is that since NC is a proxy for upper-body fat; we did not have radiographic measures to directly quantify this fat deposition.