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ORIGINAL ARTICLE
Year : 2017  |  Volume : 17  |  Issue : 3  |  Page : 162-167

Effect of obesity on nerve conduction study in an urban population of a developing country


1 Department of Physiology, Burdwan Medical College and Hospital, Burdwan, West Bengal, India
2 Department of Physiology, NRS Medical College and Hospital, Kolkata, West Bengal, India

Date of Web Publication4-Oct-2017

Correspondence Address:
Arunima Chaudhuri
Krishnasayar South, Borehat, Burdwan - 713 102, West Bengal
India
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DOI: 10.4103/sjsm.sjsm_8_17

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  Abstract 

Background: Lipids are major components of neurons. Both deficiencies of fat (malnutrition) and excess adiposity (obesity) are expected to interfere in neuronal structure and functions.
Aims: The aim of the study is to find correlation of nerve conduction study and obesity in an urban population of a developing country.
Materials and Methods: One hundred age- and sex-matched subjects willing to participate in the study were included after taking Institutional Ethics Committee clearance and informed consent of the subject. Age of the subjects was in between 18 years and 60 years. They were divided into two groups: obese and nonobese. Their weight, height, waist/hip ratio (WHR), and limb length were measured. Proximal latency, distal latency, motor nerve conduction velocity (MNCV), and F-wave latency of median and tibial nerve were recorded.
Results: Result showed a significant difference in body mass index (BMI), WHR, between the obese and nonobese group, but there was no difference in age. There was a significant difference of motor nerve conduction velocities of the right and left median nerve and the right and left tibial nerve in the obese and nonobese group of subject with obese subjects having lower values. F-wave latency of median nerve and tibial nerve were significantly higher in the obese subjects as compared to the nonobese group. BMI and WHR were negatively correlated with MNCV but positively correlated with F-wave latency. Distal latency was significantly increased in the obese group in median nerve of both sides, but in tibial nerve, no difference was found. Proximal latency was significantly increased in the obese group of all studied nerves.
Conclusion: The present study concludes that there is slowing of motor nerve conduction in obese subjects. This biological factor has to be taken into consideration while interpreting nerve conduction studies.

Keywords: Body mass index, nerve conduction study, obesity, waist/hip ratio


How to cite this article:
Majumdar S, Chaudhuri A, Ghar M, Rahaman WB, Hai A. Effect of obesity on nerve conduction study in an urban population of a developing country. Saudi J Sports Med 2017;17:162-7

How to cite this URL:
Majumdar S, Chaudhuri A, Ghar M, Rahaman WB, Hai A. Effect of obesity on nerve conduction study in an urban population of a developing country. Saudi J Sports Med [serial online] 2017 [cited 2019 Jul 19];17:162-7. Available from: http://www.sjosm.org/text.asp?2017/17/3/162/215923




  Introduction Top


One of the greatest public health challenges in the first half of 21st century is preventing the epidemic of obesity. Obesity can be defined as the excess of body fat and may result from decreased physical activity, abnormal feeding regulation, childhood overnutrition, neurogenic abnormality, and genetic factors. As populations become more westernized, dietary composition changes to include more saturated fat and less fiber.[1],[2]

As per National Family Health Survey 2007, the percentage of overweight or obese people is male 6.1% and female 7.1% in West Bengal. In some states, percentage is much higher, for example, Punjab (male - 30.3, female - 37.5), Kerala (male - 24.3, female - 34), Goa (male - 20.8, female - 27), and Tamil Nadu (male - 19.8, female - 24.4). Overall Indian picture of overweight or obese is male 12.1% and female 16%.[1],[3] Obesity is found least in Madhya Pradesh, Jharkhand, and Tripura.[1]

Indians have a more centralized distribution of body fat with thick trunk skinfolds and markedly higher mean waist/hip ratios (WHRs) for a given level of body mass index (BMI) compared to Europeans.[2] Obesity or overweight is one of the major features of metabolic syndrome and mostly due to central adiposity. Intra-abdominal adipocytes are lipolytically more active than those from other depots.[1],[2],[4]

Nerve conduction study (NCS) is essential in the diagnosis of focal neuropathies and diffuse polyneuropathies. Motor nerve conduction studies help to understand the functional status of the peripheral and central nerves. Age, height, and BMI can affect NCS.[3] Agarwal and Gaur in 2015[5] concluded that obesity causes increase in sensory and motor latency of median nerve at carpal tunnel area in women. Obesity may increase motor nerve latencies, decrease in the amplitude of action potentials and conduction velocity (CV). These changes indicate slow transmission in peripheral nerve fibers. Naik et al. in 2014[6] divided fifty-two subjects into two groups (25 in control and 27 in study group; obese) based on their BMI. Motor nerve conduction parameters (standardized distal motor latency in ms, amplitude of compound muscle action potential in mV, and motor nerve conduction velocity [MNCV] in m/s) were recorded. All the parameters depicted decreased motor CV in peripheral nerves (median, ulnar, tibial, and common peroneal) in obese individuals compared with the control group. There was a significant prolongation of latency in all nerves and decrease in amplitude except in the tibial nerve. There was also a significant decrease in CV of tibial nerve in obese subjects compared to controls.

Awang et al.[7] observed slowing of NCV in ulnar, peroneal, and sural nerve with increasing BMI. Statistically insignificant relations between anthropometric measures and sural SNAP amplitude or H-wave minimum latency were observed by Ghugare et al. in 2013.[8] No correlation was observed between anthropometric measures and sural CV or H/M ratio or H-wave maximum amplitude, and they concluded that as age advances H-wave minimum latency prolongs independent of anthropometric measurements. Werner et al. in 2012[9] studied median and ulnar sensory nerve parameters and the rate of change of those parameters with change in BMI from its baseline. As per their study, initial baseline BMI and change in BMI were never significant for any nerve measure.

The results of previous studies are conflicting, and moreover, data from studies regarding BMI and nerve CV are not available for our population. Hence, we conducted the present study to find correlation of NCV and obesity as results may help to decrease neurological complications and the socioeconomic burden resulting from obesity in a developing country.


  Materials and Methods Top


The present study was conducted in the Department of Physiology of Burdwan Medical College and Hospital during May 2014–April 2015.

Inclusion criteria

One hundred age- and sex-matched subjects willing to participate in the study were included after taking Institutional Ethics Committee clearance and informed written consent of the subject. Age of the subjects was in between 18 years and 60 years. All right-handed subjects were chosen.

Exclusion criteria

Subjects complaining of tingling and numbness in the tip of fingers or toe; alcoholics; subjects with history of fracture, neuropathy, or myelopathy disorder; subjects suffering from carpal tunnel syndrome (CTS), diabetes, leprosy, myxedema, skin ulcer, or any other disease that may affect NCV; pregnant woman or subject having pacemaker or undertreatment of cardiac arrhythmia, subjects on anticholinergics or muscle relaxant drugs were excluded from the study.

Seven hundred subjects who met the inclusion criteria and had no problem that would fit any one of the exclusion criteria from the local population were randomly chosen using an online randomizer, and anthropometric measurements were carried.

Anthropometric examination

Body weight and height were measured, BMI and WHR were calculated. Those subjects with BMI >25 were categorized as obese and those with BMI <25 as nonobese. Subjects with WHR >0.9 were considered to be obese.[2],[4]

Fifty-four subjects were found to have BMI >25, WHR >0.9. Among them, four refused to participate in the study. Hence, 50 obese subjects were selected. Among the rest 646 subjects, every 12th subject was selected for the study, and in this way, 50 nonobese subjects were recruited. Among the 50 obese subjects, 32 were male and 18 female; among 50 nonobese subjects, 31 were male and 19 female. There was no difference in age and sex between the two groups.

On first appointment, informed consent was taken, and their personal history, family history, past history, and drug history were recorded. General examination of the subjects was done. They were asked not to take any medicine which may alter the examination result before 2 days of the test. Limb lengths were measured in the standing position by nonstretchable measuring tape to the nearest 0.5 cm. Upper limb length was measured from acromion process to the tip of the middle finger. Lower limb length was measured from iliac crest to lateral malleolus.[10]

Nerve conduction study

  • Apparatus: NCS unit (Nihon Kohden Neuropack)
  • Procedure: At first, the subject was explained about the procedure and was asked to remove any jewelry, hairpin, eyeglasses with metal handle, hearing aids, or any other metal objects that may interfere with the procedure.


NCS [10] of both the right and left median nerve in case of upper limbs and both the right and left tibial nerve in case of lower limb were performed afterward. The procedure was performed in the supine position with complete physically- and mentally-relaxed state. The room temperature was kept at 26°C ± 2°C. NCS of median nerve was done with the fully extended hand, and in case of the tibial nerve, it was done with knee joint keeping in the semiflexed position.

At first, the nerve was located to be examined, and the skin over the nerve was cleaned with spirit. The recording electrode was attached to the skin over the nerve with a special paste after proper cleaning with spirit. The stimulating electrode was placed at a known distance away from the recording electrode.

The nerve was stimulated by a mild and brief electrical shock given through the stimulating electrode. The subjects experienced minor discomfort at this time, explained before the procedure.

The stimulation of the nerve and the detected response were displayed on the monitor of the NCS unit as waveform.

Calculation

From the waveform, proximal and distal latency, proximal and distal amplitude, and F-wave latency were measured. MNCV was calculated by measuring the distance in millimeter between two points of stimulation, which is divided by the latency difference in milliseconds.



D = distance between two points of stimulation

PL = Proximal latency

DL = Distal latency.

Statistical analysis

Statistical analysis was done by using the computer software “Statistical Package for the Social Sciences (SPSS) version 16 (SPSS Inc. Released 2007. SPSS for Windows, version 16.0. SPSS Inc., Chicago, IL, USA). P< 0.05* was considered as statistically significant and P< 0.01** as highly significant.


  Results Top


In the present study, 100 subjects are divided into 50 obese and 50 nonobese. Their age, weight, height, WHR, and limb length were measured. Proximal latency, distal latency, MNCV, and F-wave latency were recorded. The result showed significant difference in BMI, WHR, between the obese and nonobese group, but there was no difference in age [Table 1]. There was significant difference of motor nerve CVs of the right and left median nerve and the right and left tibial nerve in the obese and nonobese group of subject [Table 2] with obese subjects having lower values. F-wave latency of median nerve and tibial nerve were significantly higher in obese subjects as compared to the nonobese group [Table 3]. BMI and WHR were negatively correlated with MNCV but positively correlated with F-wave latency [Table 4] and [Table 5]. Distal latency was significantly increased in the obese group in median nerve of both sides, but in tibial nerve, no difference was found [Table 6]. Proximal latency was significantly increased in the obese group of all studied nerves [Table 7].
Table 1: Comparison of age, body mass index, waist/hip ratio of obese and nonobese subjects

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Table 2: Values of motor nerve conduction velocity of the right and left median nerve and the right and left tibial nerve in the obese and nonobese group

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Table 3: Values of F-wave latency of the right and left median nerve and the right and left tibial nerve in the obese and nonobese groups

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Table 4: Correlation of body mass index with motor nerve conduction velocity and F-wave latency of median and tibial nerve of both sides

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Table 5: Correlation of waist/hip ratio with motor nerve conduction velocity and F-wave latency of median and tibial nerve of both sides

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Table 6: Values of distal motor latency of median and tibial nerves of both sides in the obese and nonobese group of subjects

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Table 7: Values of proximal latency of median and tibial nerves of both sides in the obese and nonobese group of subjects

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  Discussion Top


Obesity may cause slowing of nerve conduction. If it is due to only mechanical reason, then there should be thickening of the synovial sheath which is not found in every case. There may be some type of localized metabolic problem that causes intrafascicular swelling without mechanical interference. Another possibility is that the change in pressure is a transient phenomenon that is affected by posture or activity level. An association between obesity and impaired glucose metabolism is the most likely pathophysiology to explain the occurrence of median nerve impairment among obese individuals.[11]

We conducted the present study to find correlation of NCV and obesity as results may help to decrease neurological complications and the socioeconomic burden resulting from obesity in a developing country. One hundred subjects were divided into 50 obese and 50 nonobese subjects according to their BMI; among them, 70 were male and 30 female. There was significant difference of motor nerve CVs of the right and left median nerve and the right and left tibial nerve in the obese and nonobese group of subject [Table 2] with obese subjects having lower values. F-wave latency of median nerve and tibial nerve were significantly higher in obese subjects as compared to the nonobese group [Table 3]. BMI and WHR were negatively correlated with MNCV but positively correlated with F-wave latency [Table 4] and [Table 5]. Distal latency was significantly increased in the obese group in median nerve of both sides, but in tibial nerve, no difference was found [Table 6]. Proximal latency was significantly increased in the obese group of all studied nerves [Table 7].

Awang et al. in 2006 conducted a study in 250 adult healthy Malays and divided them into four groups according to BMI. They examined median, ulnar, common peroneal nerve for both motor and sensory NCV (SNCV). They found decrease in MNCV and SNCV with increasing value of BMI.[7]

Kouyoumdjian et al. in 2002 studied 210 consecutive symptomatic CTS patients and 320 control subjects without CTS symptomatology or known systemic disorders to determine the role of personal variables as risk factors for CTS and their relationship to severity of nerve conduction abnormality. They observed that the presence of median mononeuropathy was significantly correlated to increase of BMI.[12]

In 2004, Werner et al. studied 27 obese subjects and 16 nonobese subjects with no hand symptoms to test the hypothesis that obese individuals have higher carpal tunnel pressure.

Obese individuals had slowed conduction in the median nerve across the wrist.[11]

Hsieh and Chiang in 2005 performed a case–control study including 83 patients (20 men and 63 women) with electrodiagnostic evidence of CTS cases and 82 control subjects (27 men and 55 women) at Cheng Ching Hospital. Their study revealed that the presence of median mononeuropathy was associated with increased BMI with the conclusion that obesity was a strong independent risk factor in slowing of median nerve conduction.[13]

Aygul et al. in 2009 conducted a study on 165 hands of 92 consecutive patients (81 female, 11 male) with clinical diagnosis of CTS and compared to reference population of 60 hands of 30 healthy controls (26 female and 4 male). They reported that measurement of all NCSs parameters was significantly worse in obese as compared to nonobese patients.[14]

Jagga et al. in 2011 studied the effect of aging and anthropometric measurements on nerve conduction properties and observed negative correlation of nerve CV and BMI.[15] Werner et al. in 2012 studied median and ulnar sensory nerve parameters and the rate of change of those parameters with change in BMI from its baseline. As per their study, initial baseline BMI and change in BMI were never significant for any nerve measure which contradicts our study. They only evaluated the sensory system of the dominant hand.[9] In 2012, Pawar et al. documented nonsignificant slowing of motor as well as sensory CV with increasing BMI except sural and ulnar nerve.[16] F-wave minimum latency showed a nonsignificant decrease with increasing BMI in peroneal and tibial nerve. This might be due to the fact that more superficial peroneal nerve is more dependent on subcutaneous fat thermal insulation to maintain higher perineural temperature, and thus, thinner individual may have a lower temperature around this nerve. This could account for longer latency in thinner people.[16]

In 2013, Ghugare et al. studied the impact of age, height, weight, and BMI on sural sensory and soleus H-reflex study measures in healthy central Indian population. They observed no correlation between anthropometric measures and sural NCV. They had studied only NCV of sensory sural nerve and no other parameters of NCS.[8]

Hence, from results of different studies, it may be concluded that there may be slowing of motor nerve conduction in obese subjects. This biological factor has to be taken into consideration while interpreting nerve conduction studies.

.

The present study concludes that there is slowing of motor nerve conduction in obese subjects. This biological factor has to be taken into consideration while interpreting nerve conduction studies. F-wave latency of median nerve and tibial nerve were significantly higher in obese subjects, and BMI and WHR were negatively correlated with MNCV but positively correlated with F-wave latency. Distal latency was significantly increased in the obese group in median nerve, and proximal latency was significantly increased in the obese group of all studied nerves.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Kalra S, Unnikrishnan AG. Obesity in India: The weight of the nation. J Med Nutr Nutraceuticals 2012;1:37-41.  Back to cited text no. 1
    
2.
WHO/IASO/IOTF. The Asia – Pacific Perspective: Redefining Obesity and Its Treatment. Melbourne: Health Communication-Australia; 2000.  Back to cited text no. 2
    
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Huang CR, Chang WN, Chang HW, Tsai NW, Lu CH. Effects of age, gender, height, and weight on late responses and nerve conduction study parameters. Acta Neurol Taiwan 2009;18:242-9.  Back to cited text no. 3
    
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Ko GT, Tang JS. Prevalence of obesity, overweight and underweight in a Hong Kong community: The United Christian Nethersole Community Health Service (UCNCHS) primary health care program 1996-1997. Asia Pac J Clin Nutr 2006;15:236-41.  Back to cited text no. 4
    
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Agarwal P, Gaur AK. Effect of obesity on median nerve conduction at carpal tunnel level in Indian women. Natl J Physiol Pharm Pharmacol 2015;5:21-4.  Back to cited text no. 5
    
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Naik BM, Pal P, Pal GK, Balakumar B, Dutta TK. Assessment of motor nerve conduction in healthy obese Indian population. Int J Clin Exp Physiol 2014;1:277-82.  Back to cited text no. 6
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7.
Awang MS, Abdullah JM, Abdullah MR, Tahir A, Tharakan J, Prasad A, et al. Nerve conduction study among healthy Malays. The influence of age, height and body mass index on median, ulnar, common peroneal and sural nerves. Malayas J Med Sci 2006;13:19-23.  Back to cited text no. 7
    
8.
Ghugare BW, Ramavat MR, Joshi MU, Singh R. Impact of age, height, weight and body mass index on sural sensory and soleus H-reflex study measures in healthy central Indian population. Health Agenda 2013;1:4-9.  Back to cited text no. 8
    
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Werner RA, Franzblau A, D'Arcy HJ, Evanoff BA, Tong HC. Differential aging of median and ulnar sensory nerve parameters. Muscle Nerve 2012;45:60-4.  Back to cited text no. 9
    
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Koo YS, Cho CS, Kim BJ. Pitfalls in using electrophysiological studies to diagnose neuromuscular disorders. J Clin Neurol 2012;8:1-14.  Back to cited text no. 10
    
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Werner RA, Jacobson JA, Jamadar DA. Influence of body mass index on median nerve function, carpal canal pressure, and cross-sectional area of the median nerve. Muscle Nerve 2004;30:481-5.  Back to cited text no. 11
    
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Kouyoumdjian JA, Zanetta DM, Morita MP. Evaluation of age, body mass index, and wrist index as risk factors for carpal tunnel syndrome severity. Muscle Nerve 2002;25:93-7.  Back to cited text no. 12
    
13.
Hsieh LP, Chiang DH. The relationship between obesity and the diagnosis of carpal tunnel syndrome. J Cheng Ching Med 2005;1:39-43.  Back to cited text no. 13
    
14.
Aygul R, Ulvi H, Kotan D, Kuyucu M, Demir R. Sensitivities of conventional & new electrophysiological techniques in carpal tunnel syndrome and their relationship with body mass index. J Brachial Plex Peripher Nerve Inj 2009;4:12.  Back to cited text no. 14
    
15.
Jagga M, Lehri A, Verma SK. Effect of aging and anthropometric measurements on nerve conduction properties – A Review. J Exerc Sci Pyhsiother 2011;7:1-10.  Back to cited text no. 15
    
16.
Pawar SM, Taksande AB, Singh R. Effect of body mass index on parameters of nerve conduction study in Indian population. Indian J Physiol Pharmacol 2012;56:88-93.  Back to cited text no. 16
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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