For the time being, although the coronavirus disease 2019 (COVID-19) seems to have entered a slowdown phase, researchers continue to ask questions about its pathology and treatment. One of the earliest discoveries was that anosmia was common in many patients. A new paper discusses the prevalence of this symptom in a pediatric cohort with COVID-19.
Study: Prevalence of Anosmia in 10,157 Pediatric COVID-19 Cases Multicenter Study from Turkey. Credit: Nenad Cavoski/Shutterstock
COVID-19 has hit Turkey a little hard. Case definitions for this disease come from various professional bodies, including the World Health Organization (WHO). However, the presentation and course of the disease in children differed from those in adults.
Many patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) developed fever, cough, muscle pain and weakness. Although anosmia and ageusia are less common, these symptoms are still a strong indication of this infection.
The cause of anosmia in COVID-19 is unclear but may be due to the direct inflammatory response to the virus in the nasal mucosa associated with rhinorrhea. However, this explanation is contradicted by the anosmia observed in a number of patients without congestion or rhinorrhea. This is thought to be due to inflammation of the sensory neurons of the olfactory epithelium, which consists of specialized neurons that disrupt olfactory signaling pathways.
A third possibility is that the virus invades the olfactory cortex, travels along the olfactory pathway and causes anosmia specific to COVID-19.
Anosmia as a symptom varies in prevalence with age, sex, disease severity, and geographic region. The current paper, published in The Journal of Pediatric Infectious Diseasesexamines the prevalence of anosmia in children with COVID-19 using an odor awareness survey.
What did the study show?
The study included over 10,000 patients with COVID-19. Anosmia was present in 12.5% of them. Of the approximately 1,000 cases that could be reached, over 60% were female. The mean age was ~16 years.
Most cases occurred in the 15 to 18 age group. Almost 88% of them had mild disease, 12% had moderate disease, and 0.1% each had severe or critical disease. Almost 88% had no anosmia, evenly distributed between the sexes.
The mean age of the group without anosmia was 14.7 years. The vast majority had mild or asymptomatic infection, with 6% and 1% being moderate or severe. Only 0.2% had critical COVID-19.
The patients with anosmia were predominantly female (> 60%) and the mean age was older. Ageusia was present in 84% of the cases and fatigue in half of them. Over 40% also had a cough, headache, fever and muscle aches, while over a third had joint pain.
Anosmia (and ageusia) lasted a median of 7 days. Anosmia was the only symptom in 8% of the cases. Over 40% of this subset of patients developed anosmia and/or ageusia after the onset of general symptoms, while one third had both sets of symptoms together. In one in seven cases, anosmia was the main symptom, compared to 20% in ageusia.
At one month, anosmia was persistent in less than a tenth of cases and ageusia in ~7%. When these cases were broken down by severity, only 8% of mild cases showed no resolution of anosmia, compared to 13% of moderate to critical cases.
Researchers found that patients’ scores on the odor awareness questionnaire were higher at the time of enrollment than one month later, with a median of 94 versus 46.
What are the effects?
This large case study showed an anosmia rate of 12.5%. The prevalence varies from study to study and is higher in Germany and France than in China, for example. Reasons may be due to age, gender, ethnicity, or study size bias.
However, women tend to be at a higher risk of anosmia. The exact mechanism may be controversial, but the fact that both anosmia and ageusia are the only symptoms present in a small minority of patients, coupled with the relatively late onset of these symptoms in nearly half of the cases, reduces their diagnostic value.
Nevertheless, the specificity of these symptoms indicates that as soon as they are detected, the patient should be isolated to prevent further spread of the virus.
Complete resolution of these neurological deficits is a hopeful sign in most cases (92%). It indicates that the virus is eliminated early, before neuroinvasion or viremia with mild to moderate disease occurs. In fact, critical COVID-19 is associated with a lower incidence of anosmia.
However, critically ill patients tended to have a longer period of anosmia and lower olfactory recovery rates. Recovery usually occurs within two weeks to several months and is faster in children. In the current study, the median duration of any of these symptoms was 7 days.
Treatment protocols for anosmia remain undefined, although some specialists recommend steroids and omega-3 supplements with olfactory exercises. Further research may define the long-term course of COVID-19-related anosmia.