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Smell loss and brain damage

The real research hiding behind sensational headlines
Recent press reports have caused concern among Covid-19 patients with long-term smell disorders. We investigate the story behind the headlines and why we need to be cautious in interpreting these reports.

The study attracting the attention is ‘Brain imaging before and after COVID-19 in UK Biobank’. It’s the result of work by a team at the Wellcome Centre for Integrative Neuroimaging in Oxford. Using the UK Biobank - an amazing resource of more than 40,000 brain scans from a wide range of participants - the team were able to invite hundreds of participants back to look at how their brains might have changed after Covid-19.

Their study - currently in preprint* - found a loss of grey matter in the areas of the brain directly linked to the senses of smell and taste that was consistent across participants who had been infected with Covid-19. 

It’s important to note that the study did not investigate or draw any conclusions about why, or how this change affected patients. 

Should I be worried?

No - this study does not draw any conclusions about smell loss. It highlights the importance of being able to compare brain scans before and after Covid-19. It gives scientists and doctors reliable information that they can use to explore more questions

The study itself doesn’t ask any questions about the cause, spread or long-term effects of Covid-19. For example, the study didn’t ask participants any questions about their health or wellbeing, or their sense of smell. It simply compared brain scans providing a snapshot of how parts of the brain look now compared to how they looked before. 

It’s well established that the brain adapts and changes throughout life, responding to changes in ability, environmental influences, practice, stress and disease. We also know from previous research that the size of the olfactory bulb will change as a result of smell training. Thomas Hummel’s study published in 2017 - Changes in olfactory bulb volume following lateralized olfactory training - demonstrated that the size of the olfactory bulb grew larger in people who followed a smell training program, compared with a sample group who didn’t. 

The need to know more

There are so many unanswered questions about the sense of smell, research is essential if we are to provide the correct support and treatment. Dozens of studies are going on around the world that each add to human understanding of the sense of smell, little by little. It has to be a slow and painstaking process to find answers that will eventually help patients, but sadly the slow pace of incremental understanding doesn’t make sensational headlines.

It never hurts to stop and question what you read: not everything you see on TikTok or the popular press is a faithful representation of the latest information on smell loss!

 

References 

*Note about preprint. The study is currently in preprint, which means that it still needs to be reviewed by a group of scientists to validate the quality of research. It’s only when research is accepted for publication in a respected scientific journal that doctors can start building on the knowledge it provides. If this study is accepted for publication, it will provide a good evidence base that researchers can use brain scan comparisons to help start answering some questions about the progression and impact of Covid-19 infections.

Brain imaging before and after COVID-19 in UK Biobank can be read in full https://www.medrxiv.org/content/10.1101/2021.06.11.21258690v1.full.pdf

Changes in olfactory bulb volume following lateralized olfactory training; S. Negoias, K. Pietsch & T. Hummel https://link.springer.com/article/10.1007/s11682-016-9567-9

June 21, 2021