Discussion
This is cross-sectional study highlights the prevalence and associations
of COVID-19 with anosmia and ageusia, and their impact on patients’ life
in the Kingdom of Bahrain, involving 405 patients infected between
October 2020 and June 2021.
The study reported comparable rates of anosmia and dysgeusia, with
almost half of the studied patients experiencing either or both
symptoms. A combination of anosmia and dysgeusia was more prevalent than
either of the symptoms presenting alone. olfactory and taste dysfunction
following Covid-19 is possibly underreported in the literature, as most
studies are based on self-reports rather than a more objective
assessment.
Our study’s population had a significantly higher prevalence of anosmia/
dysgeusia amongst females in comparison with their male counterparts.
Similar findings were observed in studies conducted in Saudi, Italy, and
Switzerland (13,14). However, this variation between sexes was not
significant in other studies (15-18). Possible reasons for this
variation in results across studies are the differences in methodology,
symptom definition, population studied, measurement tool and recall bias
as data was mainly dependent on self-reporting of symptoms. The
literature discusses potential biological differences between genders in
ACE receptor expression and its location on the X-chromosome, and
differences in baseline olfaction as possible explanations to the
increased prevalence of these symptoms amongst females (19,20). Both
human cell receptors ACE2 and TMPRSS2 are essential for the SARS-CoV-2
entrance. These receptors are mostly present in the olfactory epithelium
cells. Therefore, the main hypothesis is that anosmia is caused due to
damage to non-neuronal cells which, thereafter, affects the normal
olfactory metabolism. A possible explanation for the higher prevalence
among females would be that incomplete X chromosome inactivation would
contribute to increased expression of ACE2 (21).
Symptoms related to smell and taste were generally associated with
milder forms of the disease studied in the acute or initial phase (22).
It is yet not clear if these symptoms have a higher impact on morbidity
and mortality in the long term, especially with the possibility of
neurological pathophysiology. Studies have reported significant
associations of neurological burden and infection with SARS-CoV2,
explaining the potential connection with entry through the olfactory
bulb (23,24). In addition, recent studies demonstrated the association
of microinvasive SARS-CoV2 and respiratory failure, emphasising the
importance of future research on neurological impacts of COVID-19
(25,26).
In our study, smokers were more likely to experience loss of smell and
taste compared to their non-smoking counterparts, although the
difference was not found to be statistically significant. Other studies
in the region reported significant association between smoking and both
anosmia and dysgeusia (16,8). This difference could be explained by the
self-reporting of smoking through a phone call, where people might be
less comfortable reporting their behaviours (social acceptability bias).
Comparable rates of impact of anosmia and dysgeusia was reported by
other studies (4,10,27,28). The main concerns were that the senses of
taste and smell would not return, alteration of eating habits, feeling
angry and difficulty performing daily activities. While greater
attention is being paid to curbing other COVID-19 related symptoms as
well as rolling out the vaccines, the prognosis of Covid-19 survivors
with olfactory and taste dysfunction remains an enigma which will
ultimately have a huge impact on patient’s quality of life especially if
the loss or dysfunction is permanent.
Limitations of our study included measurement bias of some risk factors,
recall bias, incomplete medical records, and missing information.
Further, this study did not compare the impact of permanent vs transient
loss/dysfunction of olfactory and taste. Strengths include random
selection of an early cohort of COVID-19 patients from a national
registry and using validated tool for outcome measurement.