Early COVID-19 symptoms differ among age groups

Symptoms for early novel coronavirus (COVID-19) infection differ among age groups and between men and women, according to new research published in the journal The Lancet Digital Health.

These differences are most notable between younger age groups (16-59 years) compared to older age groups (60-80 years or older), and men have different symptoms compared to women in the early stages of COVID-19 infection, the researchers said.

For the study, led by King’s College London, researchers analyzed data from the ZOE COVID Symptom Study app between April 20, 2020 and October 15, 2020. App contributors were invited to get tested as soon as they report any new symptoms, thanks to a joint initiative with the Department of Health and Social Care. The researchers modelled the early signs of COVID-19 infection and successfully detected 80 percent of cases when using three days of self-reported symptoms.

Researchers compared the ability to predict early signs of COVID-19 infection using current National Health Service UK diagnostic criteria and a Hierarchical Gaussian Process model, a type of machine learning. This machine learning model was able to incorporate some characteristics about the person affected, such as age, sex, and health conditions, and showed that symptoms of early COVID-19 infection are different among various groups, the researchers said.

In the study, 18 symptoms were examined, which had different relevance for early detection in different groups. The most important symptoms for earliest detection of COVID-19 overall included loss of smell, chest pain, persistent cough, abdominal pain, blisters on the feet, eye soreness, and unusual muscle pain. However, loss of smell lost significance in people over 60 years of age and was not relevant for subjects over 80. Other early symptoms such as diarrhea were key in older age groups (60-79 and >80).  Fever, while a known symptom of disease, was not an early feature of the disease in any age group.

Men were more likely to report shortness of breath, fatigue, chills, and shivers, whereas women were more likely to report loss of smell, chest pain and a persistent cough.

While these models were generated in the study app, models were replicated across time suggesting they would also apply to non-app contributors. Although the models were used on the first strain of the virus and Alpha variants, the researchers said findings suggest the symptoms of the Delta variant and subsequent variants will also differ across population groups. 

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