Introduction
In December 2019, the Coronavirus Disease 2019 (COVID-19) outbreak
emerged in Wuhan, Hubei Province, China and rapidly spread throughout
the country and then evolved into a global pandemic (1). On February 12,
2020, The World Health Organisation (WHO) declared that the disease was
caused by the novel coronavirus as COVID-19(1). Efficient screening,
prompt diagnosis and isolation of the infected individuals were deemed
fundamental to contain the outbreak (2).
Several signs and symptoms were observed in some patients including
non-productive cough, fever, myalgia, fatigue, dyspnoea, diarrhoea,
nausea and vomiting, while other patients were asymptomatic (3). The
diagnosis of COVID-19 is based on the clinical suspicion, computerised
tomography (CT) findings, and a reverse transcription polymerase chain
reaction molecular test (RT-PCR) (3).
The incubation period of COVID-19 is presumed to be between 2 and 11
days, with a mortality rate reaching 2 to 4% (3). The most common
peripheral nervous system manifestations of COVID-19 include anosmia
(loss of smell) and dysgeusia (taste impairment). Although, most
patients gradually regain their sense of smell and taste, the mechanism
of these dysfunction is not fully understood (4). Post-infectious
olfactory dysfunction is thought to be the result of involvement of the
olfactory bulb and damage to the olfactory receptors cells due to the
neurotrophic features associated with SARS-CoV-2 (5). Minimal data are
available for the mechanism of taste disorders among patients with COVID
19, Single cell RNA-sequencing studies showed that epithelial cells of
the tongue express ACE-2 receptors where buccal mucosa may play a role
in entry of SARS-COV2. Additionally, indirect damage of the taste
receptors through infection and inflammation of the epithelial cells are
hypothesised to play a role in the pathogenesis. (6)
A review of the literature showed that the prevalence of anosmia ranged
between 22% to 68% (7). Regionally, a study conducted in the Kingdom
of Saudi Arabia, reported that the prevalence of olfactory dysfunction,
anosmia and hyposmia was 53%, 32.7% and 20.3% respectively. Patients
aged 15–39-year-old were mostly affected, and the prevalence of
olfactory dysfunction was higher among females (60.3%) compared to
males (56.5%) (8). In the same study, the prevalence of ageusia was
determined at 51.4% (4). The loss of taste and smell senses is mostly
transient lasting between one and two weeks. However, few chronic cases
lasting more than one year after diagnosis have been reported.
Few studies explored the impact of anosmia and dysgeusia on patients
with COVID-19 and reported negative impact of these symptoms,
interference with daily activities and deterioration in well-being
(4,9,10). A study conducted in the Eastern region of Saudi Arabia
reported that 23% of participants felt isolated, 12.6% reported having
problems with taking part in daily activities, anger in 28.2%,
difficulty in relaxing in 21% of participants, and worrying about their
ability to cope with their changes in sense of smell in 22% (4).
In view of their predominance as signs and symptoms of the disease and
in light of their substantial impact on quality of life, there is a need
to study the frequency of these two symptoms, establish their
association with COVID-19 diagnosis, and whether they are prognostic
factors for COVID-19 outcomes.
Objectives : This study aims to estimate the prevalence and risk
factors of olfactory and gustatory dysfunction in patients infected with
Covid-19 and to investigate their impact on patient’s life.