It may feel like Covid-19 has been around for years, but it's still only twelve months since the World Health Organization (WHO) declared a global pandemic.
In this relatively short space of time, several studies into Covid-19 related smell loss have now been published, and we already have a much better understanding of how the olfactory system is affected, recovery patterns and the impact of smell and taste loss and distortion.
The loss of smell and taste was recognised as one of the symptoms of Covid-19 early on in the pandemic. It’s common for a virus to cause smell and taste loss, but with Covid-19 this loss of smell and taste is a key characteristic, affecting around six out of ten patients.
People might experience a complete loss of smell (anosmia), or could find that some smells are distorted, often causing things to smell disgusting (parosmia).
Most people who experience loss or changes to their sense of smell as a result of Covid-19 completely recover in around two weeks. However, there are a small group of people - estimates are between 6 percent and 15 percent - for whom recovery can take many months, and possibly longer than a year.
Who does it affect?
Covid-19 seems more likely to affect smell in younger people. Studies showed that older people were more likely to experience fever and fatigue, with smell loss affecting younger people more.
Didn’t we know this already?
These studies confirm what people have been telling us in our Facebook groups and The AbScent Network. Patient experience is at the forefront of directing scientists where to look.
While you might question why research needs to be done to confirm what people are already saying, these studies are important. In terms of planning treatment, it’s important to understand the number of people affected using scientific techniques for gathering data. And it’s important to get this information published in scientific journals – this is where other researchers and doctors get their information from, then act on this information to better understand and treat their patients.
What about cures and treatments?
Scientists have learned that persistent smell loss is because of damage to the olfactory epithelium. This is the complex structure of cells within the nose that support the receptors that pick up aroma molecules and send signals to the brain. These cells are designed to grow back and repair the damage caused by the virus. Unfortunately, the repair or healing process will take time.
Currently there are no drugs or medical procedures that can help this repair process. But research has shown that Smell Training can help people to recover and improve their sense of smell. Doctors also recommend regular use of a nasal rinse to keep the nose clear and hygienic.
Parosmia - the experience of distorted disgusting smells - is recognised as a common phase of the healing process. There is some exciting research happening in this area which has potential to suggest future treatments to help manage the symptoms of parosmia, but research is still in the early stages.
Scientists have only just started looking at this new virus, and there is still so much to be understood. The positive news is that that large numbers of people affected has put the spotlight on this field of research, and more resources are being directed to improve our knowledge. In the meantime, we are also recognising that living without a sense of smell has a wider impact on health and wellbeing. We know, for example, that depression and anxiety are more common in people with anosmia, and that diet can be adversely affected. More research in these areas will help doctors understand and plan for the long-term care of patients.
Sources for this blog:
We have summarised the research from three recent published papers. You can read them in full:
Patient-reported olfactory recovery after SARS-CoV-2 infection: A 6-month follow-up study
High prevalence of long-term psychophysical olfactory dysfunction in patients with COVID-19
Clinical and epidemiological characteristics of 1420 European patients with mild-to-moderate coronavirus disease 2019
Evolution of Altered Sense of Smell or Taste in Patients With Mildly Symptomatic COVID-19