Intensity of neck pain and its association with anthropometric measurements

Objective This study was conducted to determine the association between intensity of pain (PI) and anthropometric measurements among patients with chronic neck pain. This cross-sectional study was conducted among high intensity of neck pain. The SiHt of the females was significantly associated with intensity of neck pain.


Introduction
Neck pain is a public health problem worldwide, common among the adult population, with one in two people suffering neck pain during their lives [1,2]. Chronic neck pain is significantly associated with their day-to-day life. It has an impact on their families, as well as on the communities and health-care systems of a country [3,4]. Economically, it is a burden to a country considering the cost of the health system, the reduced work efficiency, work absenteeism and insurance coverage [5]. It is a common issue for early retirement, sick leave, and disability [6]. The National Institute for occupational Safety and Health, estimated that the annual cost for work related Musculoskeletal Disorder was $ 13 billion a decade ago and very recently it was between $ 45-54 billion [7]. Neck pain is defined as "a pain originating from musculoskeletal tissue in the region from the occiput to the first thoracic vertebrae" [8]. It is a complex physiological, psychological, and behavioral phenomenon [8,9]. Improper posture, lower intensity stress and strain for longer periods are foremost causative factors for neck pain [10][11][12]. The cause of neck pain can vary from degeneration, trauma and mechanical causes and depends on factors such as age, gender, anthropometric measurements, physical activity, occupation, genetics, psychopathology (depression, anxiety, somatization), smoking and alcohol consumption, sleeping disorders, poor posture [13,14].
The presence of chronic neck pain may vary depending on the anatomy of the neck and anthropometric measurements of the individuals. The aim of this study was to determine the association between neck pain and the anthropometric measurements of the patients with chronic neck pain. This may provide a clearer understanding of the etiology of neck pain and a more effective management of this problem.
Running title: Intensity of neck pain and anthropometric measurements among chronic neck pain patients in Sri Lanka

Materials and Methods
The study was conducted at the Colombo South Teaching Hospital (CSTH) after obtaining ethical approval from the Ethics Review Committee (ERC) of the Faculty of Medical Sciences, University of Sri Jayewardenepura, and ERC of Colombo South Teaching Hospital. It was a cross sectional study among a convenient sample of 325 patients presented with neck pain to the rheumatology clinic at CSTH. Patients between the ages of 20 and 69 years, who had undergone radiological investigations (X-ray cervical spine-Anteroposterior and lateral) of the neck were included. Excluded from this study were, patients who had a past history of neck surgery or surgery of the cervical spine, cervical tumors or cervical ribs, patients diagnosed with metabolic bone disease (eg. osteoporosis, osteomalacia), neoplasia (eg. metastases, multiple myeloma), or bone infections (TB, osteomyelitis, abscess in the vertebral column) and pregnant females. Written informed consent was obtained from the patients. Neck pain was defined as "pain originating from musculoskeletal tissue in the region from the occiput to the first thoracic vertebrae" [8]. Chronic neck pain was defined as neck pain that lasted for more than three months [13]. A pretested interviewer administered questionnaire was used to collect the socio-demographic data and intensity of pain. Anthropometric measurements (weight, standing height, sitting height, neck circumference, absolute neck length) were recorded by the principal investigator using standard calibrated scales. The visual analogue scale 101 (0 to 100) was used to measure the intensity of pain. Patients were asked to get the average of the intensity of pain suffered during the past 7 days and record the value out of 100 [15]. Pain intensity was categorized as mild , moderate (26-50), severe (51-75) and worst possible (76-100). For purposes of calculation, mild and moderate pain was considered together as 'mild or moderate' (<50), and severe and worst possible pain was considered as one category 'severe or worst possible' (≥ 50).
Weight (kg) and standing height (cm) of the patients were recorded with light clothing and without shoes to the nearest 0.1cm and 0.1kg, respectively, and BMI was calculated as weight in kilograms divided by the square of the height in meters (kg/m 2 ) [16]. It was categorized into four groups as underweight (<18.5 kg/m 2 ), normal weight (18.5-22.9 kg/m 2 ), overweight (23-24.9 kg/m 2 ) and obese (≥25 kg/m 2 ) according to the Asia-Pacific cutoff points [16]. For purposes of calculation, overweight and obese considered as one category 'overweight or obese' (≥23kg/m 2 ).
The sitting height of the patients was measured with light clothing, without shoes and hair accessories. The patient was asked to sit on a stool looking straight a head, feet hanging down and back in contact with an upright surface. The head was kept straight having the lower border of the orbital cavities in the same horizontal plane as the external auditory meatuses. Measurements were recorded to the nearest millimeter [17].
The non-stretchable plastic tape was used to measure the neck circumference. The measurement was taken, with the patient standing upright, looking straight ahead, with shoulders down but not hunched. The measurement was taken just below the level of laryngeal prominence (Adam's apple) midway between mid-cervical spine and mid anterior neck, to within 1 mm [18].
The absolute neck length was measured as the perpendicular distance between external occipital protuberance and seventh cervical vertebra spinous process (A-B) in the lateral cervical x-ray [19] (Figure 1). The relative neck length was calculated by dividing the absolute neck length with height of an individual and multiplying it by 100 [19].  [19][20][21][22][23][24][25][26][27][28] Weerakoon TCS, Dissanayake PH, Jayakody S, Weerasekera MM, Yasawardene SG -Intensity of neck pain and its association with anthropometric measurements The following formula was used to calculate the relative neck length.

Absolute neck length x 100
Total height of individual

Statistical Analysis
Data entry and analysis was done by using the Statistical Package of Social Sciences (SPSS). Quantitative data were presented using frequency distribution and mean values. Qualitative data were presented using percentages.
Intensity of pain was defined as continuous dependent variable as well as categorical variable. Age, BMI, standing height, siting height, neck length, absolute neck length, relative neck length and neck circumference were considered as continuous variables.
Continuous variables were checked for normality, and all found to be normally distributed, therefore independent samples ttest was used to compare the mean difference between two groups. Pearson correlation was used to determine the correlation between pain intensity and anthropometric measurements. P value of < 0.05 was taken as statistically significant.

Results
Of the 325 patients who presented to the clinic with chronic neck pain, 321 patients were selected for this study according to eligibility criteria. The characteristics of the participants are summarized in Table 1 and the correlation between the anthropometric measurements and the intensity of the pain are tabulated in Table   2.   (Table 2). A statistically significant association was not seen between the intensity of neck pain and neck circumference or absolute neck length or relative neck length in both males and females.

Discussions
The etiology of neck pain is still not clear.
There are several factors that could be responsible for neck pain, its etiology, and its impact on individuals. The present study was to determine the association between intensity of pain in patients with chronic neck pain and their anthropometric measurements.
There was a statistically significant, positive correlation between BMI of the patients with chronic neck pain and intensity of the pain.
The majority of the patients studied were overweight or obese (Table 1). Of these, almost 90% had 'severe or worst possible pain'. Previous studies have demonstrated an association between obesity and neck pain. A Sri Lanka Anatomy Journal (SLAJ), 5(I) 2021, [19][20][21][22][23][24][25][26][27][28] relatively strong association between obesity and the prevalence of chronic pain in the neck, shoulders, and low back were demonstrated especially among women [20]. Another study has shown that the association of overweight and obesity with an increased risk of chronic pain in the neck/shoulders among both women and men was significant [21]. These findings could indicate that obesity may be a factor responsible for chronic neck pain.  [19].
A significant association between intensity of pain and gender was not observed in the present study. This observation is not compatible with the existing evidence, that females are more prone to have greater intensity of pain [15,25].
Few limitations should be acknowledged. This is a cross sectional study conducted among a specific group of patients with chronic neck pain, at a single centre. We have not assessed other factors which may be responsible for chronic neck pain such as: depression, engaging physical activity, hours spend for reading and watching television, smoking and alcohol consumption. Future studies should be multicentered and other confounding factors should be analyzed with the intensity of pain and anthropometric measurements.

Conclusion
Overweight or obese were more likely to have high intensity of neck pain ('severe or worst possible pain'). The sitting height of the females was significantly associated with intensity of neck pain.