A common symptom often mistaken for Covid could actually be an early sign of a deadly condition.

One in every 20 people who catch Covid-19 have long-term smell or taste problems as a result, according to a new study.

This could mean that millions of people around the world may have suffered smell and taste issues for at least six months following a Covid-19 infection.

Loss or change of sense of smell or taste can suffer “severe distress”, academics said as they urged health systems to be prepared to support people who often feel “isolated” when dismissed by clinicians.

They said daily activities such as smelling coffee and testing the flavour of food can become “disgusting and emotionally distressing”.

However, new research suggests losing a sense of smell could actually be an early sign of dementia.

Dementia, which causes people’s memories to slowly vanish is diagnosed in one in six people and is the leading cause of death in the UK.

The study found a drop in smelling abilities during a period of normal cognition predicted multiple features of Alzheimer’s disease.

Rachel Pacyna, lead author of the study, told The Sun:  “Our idea was that people with a rapidly declining sense of smell over time would be in worse shape –and more likely to have brain problems and even Alzheimer's itself –than people who were slowly declining or maintaining a normal sense of smell.”

There are currently around 900,000 people living with dementia in the UK.