Long COVID cause still unknown

A cohort study found that patients with mild or moderate COVID-19 may still experience a high burden of persistent symptoms after infection, but the causes remain unclear. The findings are published in Annals of Internal Medicine.

Many people report persistent symptoms after recovery from acute COVID-19. The causes of these persistent symptoms, a condition often referred to as "long COVID," are still unclear.

Researchers from the National Institutes of Health (NIH) studied 189 patients who were at least six weeks out from laboratory-documented COVID-19 and 120 control patients to characterize medical sequelae and persistent symptoms after recovery from COVID-19. They found that 55% of previously infected patients experienced persistent symptoms. However, the authors caution that it is probable that their study overestimates the true prevalence of long COVID as individuals with persistent post-COVID-19 symptoms were likely more motivated to enroll in the study.

The most common persistent symptoms noted in this study were fatigue, labored breathing, chest discomfort, parosmia, headache, insomnia, memory impairment, anxiety, and concentration impairment after infection. Abnormal findings on physical examination and laboratory evaluation were uncommon and occurred with similar frequency in the COVID-19 and control groups.

The authors also report that they did not find evidence of persistent viral infection or damage to tissue and organs in patients with persistent symptoms. However, those patients self-reported worsened physical and mental health and lower quality of life than either control participants or patients with COVID-19 but without persistent symptoms. According to the authors, the constellation of subjective symptoms in the absence of objective abnormalities on diagnostic evaluation resembles what has been described with other illnesses, including chronic fatigue syndrome, post-infection syndromes described after resolution of certain viral and bacterial infections, and mental health disorders such as depression and anxiety.