The risk of long-term COVID after a mild infection is about double among people who, before their COVID-19 infection, had been diagnosed as having psychological, respiratory, or general or unspecified health problems, according to a study.

The observational study, published in Nature Communications, showed that pre-pandemic conditions related to psychological, respiratory, and general/unspecified health problems were the strongest predictors for having doctor-diagnosed post-COVID problems between 90 and 180 days after the initial infection. 

It also showed that women, and individuals infected by the original (first) virus variant, had a higher risk of post-COVID complaints.

There was no strong or clear social gradient in the prevalence of the post-COVID. When accounting for virus type, vaccination was not significantly associated with the post-COVID condition, said researchers from the University of Oslo in Norway.

"These findings imply that individuals who prior to the pandemic had a psychological diagnosis were approximately twice as likely to be classified with the post-COVID condition, compared to infected individuals without such prior diagnoses," the researchers said.

The study included health data from 214,667 SARS-CoV-2–infected individuals who were diagnosed with the virus from July 1, 2020, to January 24, 2022. The mean age was 44.6 years, and 50 per cent were women. 

A total of 0.42 per cent (908) were diagnosed as having post-COVID condition (PCC). Twenty-one per cent had PCC-related respiratory problems, and 60 per cent said they experienced fatigue.

The strongest association for developing PCC was female sex and infection with the ancestral SARS-CoV-2 strain.