Study area and design on Blood supply of inner ear
The hypertension medical outpatient clinic (MOPC), the dental outpatient clinic and the ear
nose and throat (ENT) clinic at the KNH.
Study population
The study sample comprised of hypertensive patients, aged 45 to 64 years on treatment at
hypertension clinic at the KNH as cases and non- hypertensive patients attending the dental
outpatient clinic at the KNH as controls. The rationale for including patients aged 45 to 64
years is that, this is the cohort (middle aged) commonly used in hypertension studies which
aim to check for outcome; morbidity and mortality in hypertensive patients. It also reduced
the effect of presbyacusis on the study outcome. The rationale for the controls was that most
of the patients attending dental outpatient clinic were less likely to have other co morbidities
which fall under exclusion criteria (e.g head injury, renal disease etc).
Inclusion criteria
Hypertensive patients aged 45 to 64 years on treatment at MOPC at the KNH and non-
hypertensive patients aged 45 to 64 years attending dental outpatient clinic at the KNH who
gave a written consent.
Exclusion criteria
Patients with pre-existing hearing loss before hypertension, diabetes mellitus, congenital
hearing loss, head injury, temporal bone trauma, meningitis, confirmed childhood hearing
loss, ototoxic hearing loss (aminoglycosides, quinine, salicylates, cisplatin, diuretics), Noise
induced hearing loss, kidney disease and known retroviral disease. Known hypertensive
patients were also excluded from the controls. Noise induced hearing loss was determined
through history (noise exposure in a work place or residence requiring speaking with a raised
voice for at least 3 months) and late exclusion after PTA (characteristic pattern). It is almost
always bilateral sensorineural hearing loss with notching of the audiogram at 3000, 4000,
6000Hz and recovery at 8000Hz. The greatest loss is at around 4000Hz which forms acoustic
(boilers) notch.
Sample size
A study done by Saurabh Agarwal (40) showed 43.8% hearing loss in hypertensive patients
and 18 % hearing loss in non hypertensive patients. Using Fleiss, statistical methods for rates
and proportions, formulars 3.18 and 3.19 (46,47),
n
(
r 1
)
( p)(1 p)(Z Z/2 )
r(p1 p )
2
n= Sample size
Z= one sided percentage point of the normal distribution corresponding to
power of 80%, therefore Z=.84
Z = two sided percentage point of the normal distribution corresponding to
95% level of significance (0.05), therefore Z=1.96
r=1 (equal number of cases and controls)
p1= the proportion of hearing loss in the control group, p1=18%
2
2
P
p2 =the proportion of hearing loss in hypertensive group, p2=43.8%
P1 P2
2
11
0.309
1 0.309
0.84 1.96
2
n =
1
0.18 0.438
2
The sample size of the cases and controls was 51 in each arm. Therefore, the total
sample size was 102.
Sampling Procedure
Convenient sampling technique was used to recruit patients, starting with cases and
then controls. Patients attending hypertension medical outpatient clinic and on
treatment for hypertension were recruited into the study. The patients who fulfilled
the inclusion criteria and gave an informed written consent to be involved in the
study were picked by the principal researcher.
Using the preformed questionnaire, history was taken and recorded by the principal
researcher. Physical examination was done by the principal researcher. Indirect
blood pressure was measured using a proper cuff and Omron M3 automatic BP
monitor by the principal researcher. Ear (otoscopy), nose and throat examination
was done. Ear wax was found in a few patients and removed prior to tuning fork
test (TFT) and pure tone audiogram (PTA). Tuning fork tests were done using
512Hz Karl Storz stainless steel tuning fork. History, physical examination, BP
measurement, otoscopy and tuning fork test were conducted and recorded by the
principal researcher at the MOPC during routine clinic days. Patients were then sent
to the KNH ENT clinic for pure tone audiometry (PTA) which was performed by a
specific appointed qualified audiologist using an Interacoustics® clinical
audiometer AC 33.
This was done in a sound proof booth using a pure tone. Air conduction was done from 250
HZ to 8,000HZ and bone conduction from 500-4,000HZ. Pure tone average was
calculated using 500-4,000 HZ values. All the findings were recorded in the
questionnaire by the principal researcher. A total of 51 hypertensive patients were
included in the study.
Controls were then picked from patients attending the KNH dental outpatient clinic,
matching them for age (within 3 years) and sex. The same procedure as above was
followed. Consent, history taking, physical examination, BP measurement, otoscopy
and tuning fork test were performed by the principal researcher at the dental
outpatient clinic. The patients were then sent to the KNH ENT clinic where a pure
tone audiometry was conducted by the same qualified audiologist as for cases. The
procedures were conducted during routine clinic visits after patients had been
attended to by the primary clinician.
Quality control
Patient selection, history taking and examination was done by the principal
researcher to prevent inter observer bias.
Pure tone audiometry was done by a specific appointed qualified audiologist. The
same audiometer was used for all the 102 patients.
The questionnaire had been pre-tested before use and appropriate adjustments made.
Grading of hypertension was made based on the measurements obtained during the time of
study; however, it is known that blood pressure measurements can fluctuate within a given
period of time. Blood pressure can fluctuate temporarily due to stress, activity, missing a dose
of the medication, anxiety (white coat hypertension) etc. The difference is however not
exaggerated due to the physiological homeostatic balance.
Eighteen hypertensive patients had a normal blood pressure since they were on medication.
Data management and analysis
Data was collected using the formulated checklists, checked for completeness and
entered into a password-protected data entry platform. The entered data was assessed
for completeness, accuracy and consistency before analysis was commenced. Data
analysis was carried out using IBM statistics® Version 21.
Exploratory data analysis was carried out to describe the study population.
Categorical variables like gender were summarized using frequency tables.
Continuous variables like age were summarized using measures of central tendency
and dispersion such as mean, median and standard deviation.
In order to determine associations between the outcome and independent variables
such as gender and age, Pearson’s correlation was done. The patterns of hearing loss
(low, mid and high frequencies) were calculated using mean and standard deviation.
The degree of hearing loss in relation to grade of hypertension was calculated. In
each analysis, confidence intervals and p values have been used to demonstrate the
magnitude of the association.
Results were presented using tables and figures.
Ethical consideration
The study was carried out after the approval by the KNH/UON ethics and research
committee (P615/09/2015) and after obtaining authority from the KNH
management. Only those who gave informed consent were recruited in the study.
Confidentiality was maintained at all times. Raw data was stored under lock and
key, while database was protected with password to prevent access by an
unauthorized people. Use of coded data was done to ensure maximum
confidentiality. At the end of the study raw data was destroyed by paper shredding
of all hard copies and soft copy data was deleted from all storage devices including
computers, flash discs and hard disks. Results will be published in journals and
presented in medical conferences. Results may also be published in print or
electronic media where applicable. The study population will be the first to benefit
from any positive findings from the study. There was no monetary gain by the
researcher and no conflict of interest. The patients had the right to withdraw from
the research at any time without victimization and none incurred extra financial
costs.
