Mild cases of Covid-19 more likely to lose sense of smell, study finds

For people with mild covid-19, the nose may be better informed than any other part of the body. New research released Wednesday suggests that nearly 90% of people with mild illness have lost their sense of smell, a higher proportion than people with more serious illness. Although usually temporary, this loss of smell can latest six months and even longer.

The research, published in the Journal of Internal Medicine, reviewed the medical records of more than 2,500 patients with covid-19 who sought care at one of 18 hospitals across Europe. Most were ambulatory patients diagnosed with mild to moderate symptoms, while others were hospitalized with severe or critical covid-19.

In total, about three quarters of patients reported a loss of smell, medically called anosmia. But there was a big gap in the presentation of this symptom at different levels of severity. Among patients with mild illnesses, 86% reported loss of odor, compared to only 4.5% of moderate patients and 6.9% of severe patients. When looking only at patients whose odor loss was confirmed by objective testing, this gap narrowed but remained: 54.7% of these milder cases had confirmed odor loss, compared to 36.6% of moderate to critical cases.

“Olfactory dysfunction is a common disorder in covid-19 patients with a higher prevalence in patients with mild forms of the disease,” the authors wrote.

The results are consistent with previous studies showing that anosmia is a very common symptom of covid-19, even though it was under-stated in the early days of the pandemic. Other research has suggested that milder cases tend to suffer from anosmia more often. But the new study is one of the largest of its kind to examine its prevalence and to have data from patients who have had their anosmia confirmed by tests.

Although this study cannot tell us why the milder cases are more prone to lose their sense of smell, the authors have theories. The main explanation is that anosmia ironically is a sign the body is doing a decent job of fending off the coronavirus. In these patients, the infection never spreads far beyond the upper respiratory tract, thanks to a robust and localized immune response. But this answer can lead to inflammation that damages or interferes with nearby cells that help us process odor, at least for a short time.

There may also be memory issues for more severe cases. Hospitalized patients often face many and varied symptoms, while the most critical patients may require intensive interventions such as a feeding tube or ventilation. Ppatients with more severe covid-19 may simply not notice their anosmia over time. This could explain the higher anosmia rates in the study among the moderatesat-serious cases which were actually examined for it.

Fortunately, for most people who suffer from anosmia linked to covides, it appears to be self-limiting. The average time it lasted in patients was around three weeks, with around a third reporting that it only lasted two weeks. But 15% of objectively examined patients lost their sense of smell for at least two months, while just under 5% still did not recover for six months.mark of the month. Those with more severe anosmia at first were more likely to continue to experience it months later.

The authors theorize that cases of anosmia of shorter duration are often nothing more than the nasal congestion and swelling that is commonly seen with everyday colds and can temporarily block our ability to sniffle. But those who suffer from persistent anosmia probably have a more complicated problem on their hands, which means significant damage olfactory cells, either from infection or inflammation. While most people who contract covid-19 will be able to smell as they please afterwards, the scale of the pandemic – with 86 million confirmed cases worldwide in early January – means that many people could lose their sense of smell. permanently.

The authors hope their research will lead to future studies that keep an eye on these longer-term cases to better understand the phenomenon, as well as how. improve a person chance of recovery.