About one in five people around the world could have an increased risk of getting severely ill from Covid-19 because they have an underlying health condition — and this risk varies by age, a new study suggests.

The study, published in the journal Lancet Global Health on Monday, estimates that 1.7 billion people, or 22% of the world population, have at least one underlying condition that puts them at a higher risk of severe complications of Covid-19.

That ranges from less than 5% of people younger than 20 and more than 66% of those 70 and older.

“However, for many of these individuals, their condition might not be diagnosed or known to the health system, or their increased risk could be quite modest,” the researchers, from institutions around the world including the United Kingdom, United States and China, wrote.

The World Health Organization, US Centers for Disease Control and Prevention and other agencies have warned that older adults and people of any age with certain underlying medical conditions — such as lung disease, serious heart conditions, or diabetes — can be at a higher risk for severe Covid-19.

The new study included data from the United Nations on underlying health conditions among people living in 188 different countries.

While the study used data from two large studies as sources, both studies could have underestimated the prevalence of some conditions.

source CNN