Much of the research remains provisional or ambiguous, and for now scientists can’t do much better than say that covid-19 is more likely to be worse for older people — often described as over the age of 60 — and for those with chronic conditions such as hypertension, diabetes, lung disease and heart disease.
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That describes tens of millions of people in the United States alone. It also isn’t much of an explanation: The link between chronic disease and the severity of covid-19 is more in the category of correlation than causation. The “why” of the matter remains unclear.
The issue of disease variability “is the most critical question about covid,” said Edward Behrens, chief of the rheumatology division at Children’s Hospital of Philadelphia.