Wake up and smell the pandemic
Around the world people with Covid-19 have been struggling with a change in sense of smell, leading researchers at Teagasc and University College Dublin to investigate how these symptoms have been affecting people in Ireland.
The smell of freshly baked bread, the sweetness of chocolate and the cooling of mint are all examples of sensory sensations we experience while eating food. The enjoyment we get from this is mainly driven by the interaction between our senses of smell and taste, which together create our perception of flavour.
Because we have more smell receptors in our nose than taste receptors on our tongue, our sense of smell plays a key role in detecting flavour in food. That’s why when we lose our ability to smell, it can considerably impact our enjoyment of food and drink.
During the early stages of the Covid-19 pandemic, anecdotal evidence from across the world suggested that people infected with the virus were losing their ability to smell. And while it is well known that viruses that lead to the flu or common cold can often affect sense of smell, reports were growing worldwide of people experiencing a sudden loss of smell in the absence of any other Covid-19-related symptoms.
One year on from these reports, it was clear that a loss of smell is one of the most common symptoms of Covid-19 infection. While most people get back their ability to smell within a few weeks, a sizeable proportion still have not recovered and are experiencing long-term loss of smell. For these people, the impact on mental health and quality of life can be substantial.
Sniffing out the truth
At the beginning of the Covid-19 outbreak, very little information was available about how people’s perception of smell was being affected in Ireland.
To address this, researchers at Teagasc and University College Dublin (UCD) collaborated with sensory scientists across the Republic of Ireland and Northern Ireland to launch the Smell and Taste Evaluation in Ireland (STEVIE) survey.
The survey had three aims: to determine what proportion of people had lost their sense of smell, how much of it was attributed to Covid-19 and how significant these changes have been.
Of the 282 people that took part in the survey, 62% reported a change in their sense of smell. Within this group, 86% also noticed a change in their sense of taste.
Among those reporting a change in smell, 53% had not been previously tested for Covid-19, while almost 27% had tested positive and 18% had tested negative.
A quarter of people who lost their sense of smell couldn’t smell anything at all, while a third said their sense of smell was reduced, meaning smells weren’t as strong as before.
Almost 53% of people reported a daily distortion in their sense of smell, while 11% of respondents reported smelling something that was not there.
In terms of impact on eating behaviour, 50% of those who experienced a change in smell noted a decrease in their interest in and enjoyment of food, while 45% reported a reduction in appetite.
When asked how smell loss had impacted their quality of life, one-fifth of people responded that it was ‘affected greatly’. Meanwhile, two-fifths noted that it was ‘somewhat affected’. The majority of people surveyed had not spoken to a GP or physician about the changes to their smell or taste.
A persistent problem
The STEVIE study provides a snapshot of how Covid-19 has impacted a cohort of the Irish population in terms of smell loss. And the findings suggest these symptoms may negatively impact quality of life for some people in Ireland.
For a period of time following this survey, Ireland experienced the highest rate of Covid-19 infection in the world. Given this, it’s likely that persistent smell dysfunction is affecting a proportion of those recovering from Covid-19 in Ireland.
Supporting this idea is the fact that an Irish Facebook group called Tasteless Cuisine was set up recently to support those suffering from smell and taste loss as a result of Covid-19. Support is also available through charities advocating on behalf of those impacted by smell and taste loss, such as AbScent and Fifth Sense.
In order to help those affected, further research is needed to ascertain the full extent of smell and taste dysfunction in Ireland, and the most promising interventions and treatments need to be identified.
Understanding the different types of smell disorders
There are a number of disorders that can affect our sense of smell, and Covid-19 has been associated with each of them. It can be confusing to keep track of the different terms, so here we’ve provided a simple explanation of four of the most common smell disorders brought on by Covid-19.
Anosmia a complete loss of smell
Hyposmia a reduced sense of smell
Parosmia a distorted sense of smell, often from pleasant (like freshly baked bread) to unpleasant (like sewage or burning rubber)
Phantosmia smelling things that aren’t there (like smoke or burnt toast)
We thank Rufielyn Gravador for assistance with data analysis and also acknowledge the partners of Sensory Food Network Ireland for their contributions towards this study.
Emily Crofton, Department of Food Quality and Sensory Science, Ashtown Food Research Centre, Teagasc, Dublin. firstname.lastname@example.org
Eimear Gallagher, Head of Department of Food Quality and Sensory Science, Ashtown Food Research Centre, Teagasc, Dublin.
Sinéad McCarthy, Agrifood Business and Spatial Analysis, Rural Economy and Development Programme Teagasc, Athenry, Co. Galway.
Emma Feeney, Institute of Food and Health, University College Dublin, Dublin.
Hopkins, C. and Kelly, C. (2021) ‘Prevalence and persistence of smell and taste dysfunction in COVID-19; how should dental practices apply diagnostic criteria?’, BDJ in Practice, 34, pp. 22–23.