|Year : 2012 | Volume
| Issue : 1 | Page : 3-6
A study of gender, head circumference and BMI as a variable affecting BAEP results of late teenagers
Jayesh D Solanki, Naisargi Joshi, Hemant B Mehta, Chinmay J Shah
Department of Physiology, Government Medical College, Bhavnagar, Gujarat, India
|Date of Web Publication||10-Jul-2012|
Jayesh D Solanki
Department of Physiology, Government Medical College, 4th floor, Behind S. T. Bus Stand, Jail Road, Bhavnagar- 364 001, Gujarat
Source of Support: None, Conflict of Interest: None
Background : Influence of sex on brainstem auditory evoked potential (BAEP) is not well understood with few studies in India that targets young Teenagers. Aim : Our study aimed to look into gender, head circumference, and body mass index (BMI) as a factor affecting BAEPs of healthy late teenagers. Materials and Methods : BAEP responses were elicited in age-matched teenager college students using standard protocol. Results of absolute latencies and interpeak latencies (IPLs) were compared among Male and female groups and compared for significance as such and after normalizing head size and BMI and tested for significant difference, if any. Results: Latencies and IPLs of BAEP were lower in males when compared with females, but significance was found only for the later parameter. IPLs showing significant gender difference were for I-III and III-V but not I-V. When test groups with comparable head size and BMI were compared, the difference decreased with neither of the parameter being statistically significant. Conclusion: Utility of BAEP can be optimized by establishing normative data for every setup based on BMI and head circumference along with age and gender before using it as a clinical tool.
Keywords: Body mass index, Brainstem auditory evoked potential, Inter peak latencies, Latencies
|How to cite this article:|
Solanki JD, Joshi N, Mehta HB, Shah CJ. A study of gender, head circumference and BMI as a variable affecting BAEP results of late teenagers. Indian J Otol 2012;18:3-6
|How to cite this URL:|
Solanki JD, Joshi N, Mehta HB, Shah CJ. A study of gender, head circumference and BMI as a variable affecting BAEP results of late teenagers. Indian J Otol [serial online] 2012 [cited 2015 Apr 26];18:3-6. Available from: http://www.indianjotol.org/text.asp?2012/18/1/3/98276
| Introduction|| |
Evoked potentials are ancillary neorodiagnostic tools applicable to many fields,  allowing assessment of conduction of sensory impulses in central  and peripheral  nervous system. Brainstem auditory evoked potentials (BAEPs) are recorded from scalp as small voltage potentials within 10 ms after applying a sound stimulus and also known as short latency responses.  As an affecting factor age ,, and hearing loss are well proven in various studies, but gender and head size have shown variable results in different studies for different subgroups and body mass index (BMI) which depends on height and weight has never been tested. Very few normative studies are done in India and none in our state. An Indian study  suggested no gender difference in BAEPs between 3 and 13 years age group, but in the age group 16-45 years it was found evident in another study.  This study tried to test this gender bias hypothesis for BAEP results in different sex groups of age 16-19 years and inquired whether head circumference and BMI are source of variance responsible as a cause of gender difference or not.
| Materials and Methods|| |
This study was done at Electrophysiology Lab, Department of Physiology, Government Medical College, Bhavnagar, from March 2009 to April 2009. After taking approval from Institutional Review Board, 48 medical students were selected in the age group 17-19 years (24 males and 24 females) having normal audiometric hearing. A detailed history and clinical examination were undertaken to rule out any secondary cause of neurological deficit. The subjects of this study coming from various part of the state formed a fairly representative sample of this region.
After taking written consent and explaining procedure to subjects, anthropometric data were taken. Readings were taken in sitting position with stabilization of head to minimize any muscle activity to avoid interference in BAEP recording. BAEP was performed using PC-based machine RMS EMG EP MARC-II and EEG electrodes. Methodology used was standardized as recommended by the International Federation of Clinical Neurophysiology committee  using 10-20 International System for electrode placement. Reference electrode was placed on the forehead at Fz position on the forehead above Nasion. The ground electrode was placed on vertex Cz and active electrode was placed on left and right mastoid of each ear. The electrode impedance was kept at 5 k ohm. BAEP was produced by a brief click that stimulates headphones at 11.1 per second at intensity of sound 60 dB. Computerized averaging and superimposing of recording were done. A series of five waves were recorded during the first 10 ms after giving the auditory click stimulus. Absolute latencies of waves I, II, III, IV, and V and interpeak latencies (IPLs) between waves I-III, III-V, and I-V were recorded for each ear separately.
The data were recorded on a predesigned validated Performa and was then transferred onto an Excel spreadsheet. Variables were assessed for approximate normality and then were summarized by mean and standard deviation. GraphPad statistical software was used for data analysis and unpaired Student's t test was used to check the significance with P value of less than 0.05 being considered statistically significant.
| Results|| |
This study tested BAEP latencies of age-matched late teenage healthy medical students divided into male and female groups.
Comparison of anthropometric data of two groups showed significant difference in head circumference, height, and weight but not in BMI and age [Table 1].
There was slight prolongation of latencies of various BAEP waveforms in males when compared with females but proving statistically insignificant, and the same trend was observed for IPLs for which significance was found between I-III and III-V but not for I-V [Table 2].
|Table 2: BAEP latencies and interpeak latencies of male and females (mean ± SD)|
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Gender difference was further tested after choosing subjects with comparable head sizes that revealed the same latency prolongation in males when compared with females, but the magnitude of difference diminished with no statistical significance for either latencies or IPLs [Table 3].
|Table 3: BAEP latencies and interpeak latencies of male and females having comparable head sizes (mean ± SD)|
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Two groups were further divided into subgroups having low BMI (<18.5) and normal BMI (>18.5). The results showed lower latencies in low BMI group when compared with normal BMI group. Comparison of BMI-matched individuals of male and female groups showed larger latencies and IPL in males when compared with females that were statistically insignificant [Table 4].
|Table 4: BAEP latencies and interpeak latencies of male and females having comparable head sizes (mean ± SD)|
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| Discussion|| |
This study tested the influence of sex on BAEP latencies in late teenagers of either sex. Results revealed that males had longer absolute latencies and IPLs than females as in line with previous studies. ,,,,, However, the differences were significant only for IPLs and not for individual waveform latencies directly suggesting that in younger population IPLs are more useful than absolute latencies.
The cause of underlying male disadvantage can be (i) comparatively smaller head circumferences in females when compared with males, ,, (ii) effect of sex hormone, , and (iii) difference in core temperature. , However, the later two are not well-proved factors so we tried to look at the effect of the first one. The gender-based study groups may have significant variation in height and weight that can be reflected in BMI as seen in this study and no study has ever focused the attention on BMI as a variable affecting BAEP latencies which was looked for in this study.
Tandon and Mishra  found that gender difference starts around 16 years of age for BAEP latencies. But this study showed that the gender difference is present insignificantly for all absolute latencies and it is further reduced when we take them for head circumference and BMI, suggesting their probable role in the root of sex difference observed. This further reinforces the fact that head size that reflects brain size  is one of the important factors for the basis of gender differences in BAEP latencies. In contrast to studies done outside India, we do not find any difference for waves I, III, and V that is consistently reported by other researchers, ,,, but IPL difference was still prevalent at least for I-III and III-V.
BMI is a physiological parameter that affects many measured body parameters. In our study, females and males had significant difference in height and weight, but when these values were turned into BMI the difference changed into an insignificant parameter among both groups. Low BMI resulted in lower latencies and normal BMI in a comparatively higher one. This may direct us to a fact that BMI should be considered as a variable while establishing a norm for BAEP standards.
| Conclusion|| |
Statistical insignificance of BAEP latency differences among different comparable gender groups in this study excludes gender as a basis for variation in BAEP and results in late teenage healthy subjects in our region. It suggests IPL difference as more useful tool than merely waveform latencies. BMI and head circumference proved to be a variable, affecting the outcome that needs to be considered. The diagnostic utility of BAEPs can be improved by taking into consideration these physiological variables. It rejects sex as a possible systemic source of variance for BAEP results up to the end of teenage life in our population and needs further elaboration for re inforcement of this observation.
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[Table 1], [Table 2], [Table 3], [Table 4]
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