Pune: In a study conducted by the Indian Institute of Science, Education and Research (IISER) in Pune it was found that the smelling capacity was severely affected among the Covid-19 symptomatic patients. Similarly, the study also talks about how the olfactory (connected with the sense of smell ) loss or deficits in the sense of smell due to Covid-19 infection had just begun to be reported.
The study was published in the journal Current Research in Neurobiology, Nixon Abraham’s group at IISER Pune reported on persistent olfactory learning deficits during and after post-COVID-19 infection. This work was carried out in collaboration with researchers from BJ Government Medical College and Sassoon General Hospitals, Pune.
While talking to Free Press Journal Abraham said, “My group works on deciphering the neural circuits involved in olfaction, or the sense of smell, with the goal of obtaining insights into animal behavioural responses, decision-making processes, and brain function in health and disease."
Abraham’s group chose to probe the matter and initiated a collaboration with doctors from BJ Government Medical College and Sassoon General Hospitals in Pune during the Covid-19 time and the study is still being carried out.
Here's how the research was conducted
Explaining the process, he said, “Experiments that involve the study of the sense of smell, the group employed an olfactometer, a device to deliver odour stimuli in a controlled manner. Working through the early months of the COVID-19 pandemic in 2020, the group custom-built a special version of the olfactometer with built-in safety precautions for preventing the transfer of infection during the study and thus to be able to conduct an olfactory fitness study in COVID-19 patients.”
Their results, published in October 2020 in eClinical Medicine, had identified deficits in the sense of smell in over 80% of asymptomatic carriers. In the new paper published in March this year, the team conducted a high-precision quantitative assessment of the ability to smell in four groups of people - symptomatic COVID-19 patients, asymptomatic COVID-19 carriers, those who recovered from COVID-19 infection, and healthy individuals.
Participants in the study were presented with certain odours at intervals and the following aspects were looked for and measured quantitatively by the team - did the participant detect the odour correctly, were they able to tell apart one odour from another (olfactory matching accuracy), and were there any changes to olfactory matching accuracy after multiple sessions (olfactory learning).
The team then compared and analysed data they gathered via the olfactometer from each of these sessions, which together represented about 12,000 behavioural read-outs from a total of 200 participants.
The team made the following observations:
Detectability indices and olfactory matching accuracies were significantly lower for symptomatic COVID-19 patients in comparison to healthy subjects. This observation was consistent for all concentrations tested using 10 different odorants (types of smells).
Symptomatic patients and asymptomatic carriers showed differential odour detectability and olfactory function scores
Read-outs from COVID-19 patients and recovered individuals pointed to severe and persistent deficits in olfactory learning.
“Such precise quantification of the sense of smell, where we were able to get information on both the sensory and cognitive deficits caused by COVID-19 infection, was made possible because of the olfactometer that we custom-built. Its design prevents cross-contamination between different tests, which is a unique feature, and also allows us to generate stimuli of varying complexity by using multiple odours,” said Dr Nixon Abraham.
“We hope to further develop this method to screen for neurodegenerative conditions and infections that affect the sense of smell and to identify conditions such as hyposmia and anosmia at early stages. This work has received research grant support from the DST-Cognitive Science Research Initiative, Govt. of India and DBT/Wellcome Trust India Alliance”, he informed.
