Keywords
behavioral threshold - pure tone audiometry - ABO classification - blood group
Introduction
Sight, hearing, taste, touch, and smell are the five senses of a human being. Among
these five, hearing is the sense which helps us to enjoy the sounds and conversations.
Hearing is the process where we pick up sounds and attach it to the meaning. Scientifically
it is the process in which sound travels in invisible waves created by the vibrations
of particles. Human ear can process very quiet sounds as well as extremely loud sounds.
Humans are capable of hearing frequencies between 20 Hz and 20,000 Hz, and have a
fairly narrow range of hearing compared to other species. This range is known as the
audio or sonic range. Any difficulty or inability to hear the sounds in the audio
range is termed as hearing impairment or hearing loss.
Blood is a body fluid in humans and other animals that delivers nutrients and oxygen
to the cells and transports metabolic waste products away from those same cells.[1] Blood is classified based on the presence and absence of antigens and antibodies
on the surface of red blood cells (RBCs). Based on the antigen property of the blood,
all human beings can be classified into four groups.[2] These human blood groups are as follows: antigen A with antibody B—group A, antigen
B with antibody A—group B, antigen AB with no antibodies—group AB, and antigen nil
with antibody A and B—group O. Blood group O is the most common blood group (37.12%)
followed by B (32.26%) and A (22.88%); the least prevalent blood group is AB (7.74%).
Effect of blood group on some of the aspects of otoacoustic emissions (OAEs) including
magnitude were studied. OAE status is indicative of outer hair cell functioning in
the cochlea. OAE amplitude was found to be reduced in women aged between 18 and 26
years having O+ blood group.[3] In individuals with O+ blood group, noise-induced hearing loss (NIHL) was determined
to be significantly more frequent which indicated that individuals with O blood group
are more prone to develop NIHL.[4] Assessment was done for spontaneous otoacoustic emissions (SOAEs), transient-evoked
emissions (TEOAEs), and distortion-product otoacoustic emissions (DPOAEs) of positive
blood groups among which individuals with O blood group were found to have fewer occurrence
of SOAEs and showed reduced amplitude in some of the frequencies for DPOAE when compared
to the individuals with blood group B.[5] OAE amplitude was found to be reduced in participants with blood group O when compared
to those with blood groups A, B, and AB. This finding was supportive of the hypothesis
that individuals with different blood groups may have different OAE amplitude values.[6] Along with monitoring the OAEs, it is also important that regular monitoring of
the hearing thresholds be carried out to extensively monitor the hearing sensitivity.
Studies have been focused on identifying the relation between blood group and OAE
amplitude. However, there is a dearth in literature that identifies the relation between
blood groups and the behavioral hearing thresholds. The present study could serve
as a baseline to understand the relation between blood groups and the behavioral hearing
thresholds.
Aims and Objectives
The present study aims to identify the relationship between different blood group
and behavioral thresholds (pure tone audiometry [PTA]) among individuals within the
age range of 18 to 40 years (young adults). The objectives of the study are to
-
Identify if there is a difference in the PTA thresholds of individuals with different
blood group.
-
Explore the difference in the PTA thresholds across gender within a particular blood
group.
-
Identify the difference in the PTA thresholds between right and left ear of individuals
within a particular blood group.
Methods
The study included 80 participants, who were further grouped according to their blood
group. Four blood groups (A, B, O, and AB) were considered for the study. Only RH-positive
blood group was considered for the study. Each group consisted of 20 participants,
with 10 males and 10 females. Participants were within 18 to 40 years of age and had
accurate knowledge of their blood group. The participants had reported no history
of ear infection, prolonged noise exposure, or major health problems. Participants
with the history of middle ear pathology or inner ear pathology were excluded from
the study. Each participant completed a detailed case history questionnaire prior
to the threshold determination. All participants provided the information regarding
their age, blood group, hearing, and medical history. Immittance was done to rule
out middle ear pathology, PTA was performed at frequencies from 125 Hz to 20 kHz in
both the ears using AC 40 clinical audiometer with supra-aural headphones with appropriate
calibration. The stimulus used for PTA was pure tones of specific octave frequencies
(from 125 Hz to 20 kHz). Threshold determination was done using 1 db step. Statistical
analysis was done using SPSS version 17. MANOVA and Bonferroni post hoc analysis was
used for statistical analysis.
Results and Discussion
The present study aims to identify the difference in behavioral thresholds of individuals
with different blood groups, in males and females. Mean and standard deviation of
the thresholds for each blood group was derived from descriptive statistics and is
depicted in graphs 1 to 4. Results of the study suggest that thresholds of right ear
are better than the thresholds of left ear in both males and females. MANOVA test
was administered on the data to observe variation between the groups. Results of the
parametric test revealed statistically significant difference only for right ear (1.830
[57,108.106]; p = 0.04). There was no statistically significant difference for thresholds of left
ear across the blood groups at p > 0.05. Results indicate hearing thresholds of the right ear were better both in
males and females; this can be attributed to the slight anatomical difference in the
right auditory pathway. Bonferroni post hoc analysis was carried out for multiple
comparisons and there was no statistically significant difference in behavioral thresholds
of different blood groups. This may be because of the noninfluence of different blood
group antigens on outer hair cell functioning. Although the role of antigens in outer
hair cell development and differentiation of inner ear parts are well acknowledged,
it has no impact on the overall functioning of the inner ear. The biological role
of human blood group antigens in tissue functions remains controversial.[7] However, there are no evidence-based studies to explain why there is no difference
in behavioral thresholds in different blood groups even though there is a difference
observed in studies based on OAE ([Fig. 1]
[Fig. 2]
[Fig. 3]
[Fig. 4]).
Fig. 1 Mean and SD of behavioral thresholds from 250 Hz to 20 KHz in both ears for males
and females (MR, male right; ML, male left; FR, female right; FL, female left) in
blood group A. SD, standard deviation.
Fig. 2 Mean and SD of behavioral thresholds from 250 Hz to 20 KHz in both ears for males
and females (MR, male right; ML, male left; FR, female right; FL, female left) in
blood group B. SD, standard deviation.
Fig. 3 Mean and SD of behavioral thresholds from 250 Hz to 20 KHz in both ears for males
and females (MR, male right; ML, male Left; FR, female right; FL, female left) in
blood group AB. SD, standard deviation.
Fig. 4 Mean and SD of behavioral thresholds from 250 Hz to 20 KHz in both ears for males
and females (MR, male right; ML, male left; FR, female right; FL, female left) in
blood group O. SD, standard deviation.
Conclusion
The present study aimed to identify the difference in behavioral thresholds in different
blood group in males and females. Findings reveal thresholds were better in right
ear in males and females; however, there was no significant threshold difference noticed
in a specific blood group, indicating that behavioral thresholds do not vary significantly
among different blood groups. Further investigation on the potential link between
ABO blood group and auditory status, including differential effects of noise exposure
on cochlear function, is needed.
