LITERATURE REVIEW
Hearing loss has multi-factorial causation and hypertension
Hearing loss has multi-factorial causation and hypertension is one of the preventable risk
factors. Studies outside Africa have shown a link between hypertension and hearing loss with
prevalence ranging from 7.3% to 59.2%. The studies have also shown an association between
duration & severity (grade) of hypertension and the prevalence and degree of hearing loss.
The data on prevalence, patterns of hearing loss, degree of hearing loss in relation to
hypertension is scanty in sub-Saharan Africa. The audiological tests used to asses hearing loss
are PTA, ABR and OAE. Saurabh Agarwal et al (40) in 2013 did a case controlled study on
the effects of hypertension on hearing. The study conducted in India had 150 cases and 124
controls both genders aged between 45-64 years with males comprising 65.8%. Hearing was
assessed by measuring pure tone threshold at 250 - 8,000 Hz. They found that the p value
calculated by Pearson’s correlation method was less than 0.001 showing a significant
association between hypertension and increase in hearing thresholds. In the study, there was a
mild hearing loss in 18 % of patients without hypertension, 36.7 % of patients with grade 1
hypertension, grade 2 hypertension had 40.4% while they were 54.2% of the patients with
grade 3 hypertension. Grade 3 hypertensive patients had a longer duration of hypertension, a
mean of 9 years while those with grade 1 had a mean duration of 3.7 years. The results thus
showed that duration and severity of hypertension increase risk of hearing loss.
Marchiori et al (4) in 2004 did a non-paired case-control study on hypertension as a factor
associated with hearing loss. The study was conducted in South Brazil and had 154 cases with
hearing loss and 154 controls without hearing loss, both genders, aged 45 to 64 years. Women
predominated with 57.8% in cases and 77.3% in controls. Pure tone audiometry was used for
hearing assessment. Seventy two (46.8%) of the cases, had hypertension and hearing loss
while 108 (70.1%) without hearing loss (controls) did not have hypertension. The degree of
hearing loss was mild in 62% of the cases. They concluded that hypertension was
significantly associated with hearing loss.
In 2014 in Mumbai, Harish Chander Goel et al (41), conducted a prospective age and sex
matched study on the effect of systemic hypertension on inner ear functions. The study had 50
cases with hypertension and 50 controls without hypertension age and sex matched. They
found that hearing threshold levels by PTA were raised in all frequencies along with impaired
vestibular functions (10%) in hypertensive patients and correlated with the degree of
hypertensive retinopathy changes. All cases with moderate SNHL had grade II retinopathy
while 68% of the cases had hearing loss. Hypertension is postulated to cause inner ear
vascular disorders and to impair its function in a similar way as of hypertensive retinopathy.
Distortion product Otoacoustic emissions (DpOAE) were not evident in the octaves from 2 to
5 KHz in 22% of patients suffering from hypertension as opposed to 8% of controls.
Chen YL and Ding YP (3) in 1997 did a Prospective case-control study on relationship
between hypertension and hearing disorders of the elderly. The study was conducted in
Shandong province, China. It included 50 subjects with hypertension (cases) and 50 subjects
without hypertension (controls) all males aged between 55 and 89 years. Pure tone
audiometry and ABR was done. The hearing thresholds by PTA increased with age more in
the hypertensive patients. ABR showed prolonged absolute latencies of wave V and inter peak
latency of wave I-V and III-V. The duration and complications of hypertension also had
influence on hearing impairment.
Altuntas EE et al (42) in 2012 did a prospective, case-control study to compare the ratio of
hearing loss evaluated with transient evoked otoacoustic emission (TEOAEs) testing in
normal and hypertensive pregnant women during the first week after delivery in Cumhuriyet
university hospital, Turkey. Cases included 96 women with gestational hypertension,
preeclampsia, eclampsia or HELLP (hemolysis, elevated liver enzymes, low platelet count)
syndrome, while the controls included age-matched 107 women with normal pregnancy.
Preeclampsia is a vascular disorder which affects microcirculation and would be expected to
cause cochlear dysfunction. Hearing loss demonstrated using TEOAE during the first
postpartum week was detected in seven (7.3%) women in the hypertensive pregnancy group
and in three (2.8%) women without hypertension. Both TEOAEs and PTA results were not
statistically significantly different in the cases and controls. However hearing loss detected
using TEOAEs was significant in the HELLP syndrome group.
Sogebi (43) did a prospective, comparative, hospital-based study in Nigeria using PTA to
asses hearing. He had 76 subjects with SNHL and 51 controls without SNHL age and sex
matched. Age ranged between 45-94 years and males were 59.8%. Logistic regression
analysis revealed that hypertension, with odds ratio (OR) =7.5 and P=0.010, had significantly
increased odds of developing SNHL. The other risk factors included family history of hearing
loss (OR= 26.3), head injury (OR=56.8), noise exposure (OR=17.3), ototoxic drugs (OR=6.3)
and cigarette smoking (OR=19.2). The extreme of age may have had an influence on the
results as the prevalence of hearing impairement is higher after 65 years.
Hutchison et al (44) in a cross sectional study conducted in United States of America with 101
participants aged between 10-78 years examined the correlation between cardiovascular
health (including hypertension) and hearing function. Hearing assessment was done by PTA
and DpOAEs. They found that the lower the cardiovascular fitness and the higher the age, the
worse the PTA at high frequencies (2 & 4 KHz). OAEs were better for the cardiovascular fit
subjects but not statistically significant.
In 2007 Mondelli & Lopes (45) did a retrospective review using pure tone audiometry,
auditory anamneses and tympanogram to assess hearing loss. The study conducted in Brazil
comprised of 392 patients with hearing loss aged between 45-60 years. They found
that 232 (111 males and 121 females) had hypertension and hearing loss (59.2%).
Moderate SNHL was at 56.7% and tinnitus at 43.7%.
REFERENCES
1. World Health Organization.WHO global estimates on prevalence of hearing loss,
based on 42 population based studies[Internet].2012 [Cited 2015 july 10].
Available from http://www.who.int/pbd/deafness/estimates.
2.Mark David Joshi, Richard Ayah, Elijah Kaharo Njau, et al. Prevalence of
hypertension and associated cardiovascular risk factors in an urban slum in Nairobi,
Kenya: A population-based survey.BMC Public Health 2014; 14:1177.
3.Chen Y L, Ding Y P. Relationship between hypertension and hearing
disorders in the elderly. East Afr Med J.1999;76(6):344-347.
4.Luciana Lozza de Moraes Marchiori; Eduardo de Almeida Rego Filho; Tiemi
Matsuo. Hypertension as a factor associated with hearing loss. Rev. Bras.
Otorhinolaringol.2006;72(4).
5.Galina N. O, Oburra H, Aluoch JR.Sensorineural hearing loss in patients with
sickle cell anaemia in Kenya. East Afr Med J. 1996;73(7):471-473.
6.Vincent N. Carrasco; Jiri Prazma; James E. Faber et al. Cochlear
Microcirculation :Effect of Adrenergic Agonists on Arteriole Diameter.Arch
Otolaryngol. Head Neck Surg.
1990;116(4):411-417.
7.Gates GA, Cobb JL, D'Agostinho RB, et al. The relation of hearing in the
elderly to the presence of cardiovascular disease and cardiovascular risk factors.
Arch Otolaryngol. Head Neck Surg. 1993;119:156-161.
8. Bachor E, Selig YK, Jahnke K, et al. Vascular variations of inner ear. Acta
Otolaryngol. 2001;121:35-41.
9. Axelsson A and Ryan AF. Circulation of the inner ear: Comparative study of
vascular anatomy in the mammalian cochlea. In: Physiology of the ear, edited by
Jahn AF and Santos– Sacchi J. New York: Raven Press, 1988; p. 295–315.
10. Axelsson A. Comparative anatomy of cochlear blood vessels. Am J
Otolaryngol.1988; 9: 278–290.
