Covid-19 early infection symptoms may differ among age groups, says study

Symptoms for early infection of Covid-19 can differ among age groups and between men and women, according to new research.

The research paper has been published in the Lancet Digital Health. The study was led by researchers from King’s College London who analysed data from the ZOE Covid Symptom Study app between April 20 and October 15 2020.

The contributors of the app are invited to get tested as soon as they report any new symptoms, owing to a joint initiative with the Department of Health and Social Care.

The researchers modelled the early signs of infection of Covid-19. They were able to successfully detect 80 per cent of cases within three days of self-reported symptoms.

They compared the ability to predict early signs of infection using current National Health Service UK diagnostic criteria and a Hierarchical Gaussian Process model, a type of machine learning.

Certain specific characteristics about the person affected, such as age, sex, and health conditions were incorporated into the ML model which then showed that symptoms of early Covid-19 infection are different among various groups.

Researchers examined 18 symptoms which had different relevance for early detection in different groups.

Disease detection

For earliest detection of the disease, the most important symptoms to consider overall included loss of smell, chest pain, persistent cough, abdominal pain, blisters on the feet, eye soreness and unusual muscle pain, as categorised in the study as per an official news release by King's.

As per the research, the differences in symptoms are most notable between younger age groups (16-59 years) as compared to older age groups (60->80 years). During the early stage of infection, men have different symptoms compared to women, it further added.

The loss of smell was significant in people over 60 years of age. However, it was not found to be relevant for subjects over 80.

Other early symptoms such as diarrhoea were key in older age groups (60-79 and >80). A known symptom of Covid, fever, was not an early sign of the disease in any age group.

When it comes to differences between men and women, men were more likely to report shortness of breath, fatigue, chills and shivers, whereas women were more prone to reporting loss of smell, chest pain and a persistent cough.

Symptoms profile

Though the models were generated in the app, they were then replicated across time. This was to ensure that they would also apply to non-app contributors.

Furthermore, the models were used on the first strain of the virus and Alpha variants. However, as per the key findings, it is likely that the symptoms of the Delta variant and subsequent variants will also differ across population groups.

Lead author, Claire Steves, Reader at King’s College London said, “Its important people know the earliest symptoms are wide-ranging and may look different for each member of a family or household," as quoted in the news article by King's.

"Testing guidance could be updated to enable cases to be picked up earlier, especially in the face of new variants which are highly transmissible. This could include using widely available lateral flow tests for people with any of these non-core symptoms,” Steves added.

Dr Liane dos Santos Canas, first author from King’s College London, said, “Using a larger number of symptoms and only after a few days of being unwell, using AI, we can better detect Covid-19 positive cases. We hope such a method is used to encourage more people to get tested as early as possible to minimise the risk of spread.”

“As part of our study, we have been able to identify that the profile of symptoms due to Covid-19 differs from one group to another. This suggests that the criteria to encourage people to get tested should be personalised using individuals' information such as age. Alternatively, a larger set of symptoms could be considered, so the different manifestations of the disease across different groups are taken into account," said Dr Marc Modat, Senior Lecturer at King’s College London.

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