About 400 million people worldwide have been afflicted with long Covid, according to a new report by scientists and other researchers who have studied the condition. The team estimated that the economic cost — from factors like health care services and patients unable to return to work — is about $1 trillion worldwide each year, or about 1 percent of the global economy.

The report, published Friday in the journal Nature Medicine, is an effort to summarize the knowledge about and effects of long Covid across the globe four years after it first emerged.

It also aims to “provide a road map for policy and research priorities,” said one author, Dr. Ziyad Al-Aly, the chief of research and development at the V.A. St. Louis Health Care System and a clinical epidemiologist at Washington University in St. Louis. He wrote the paper with several other leading long Covid researchers and three leaders of the Patient-Led Research Collaborative, an organization formed by long Covid patients who are also professional researchers.