Flawed Study Design Hinders Research on Infection-Associated Chronic Illnesses

Each year, thousands of Americans develop chronic persistent symptoms—including fatigue, cognitive difficulties known as "brain fog," and other debilitating issues—after acute infections from pathogens such as those causing Lyme disease and COVID-19. Despite years of effort, attempts to pinpoint causes and develop treatments have come up short. According to 16 leading researchers, part of the problem lies in how these studies are designed.

In an article published in Brain, scientists from Rutgers University, the National Institutes of Health, Rockefeller University, New York Medical College, the Icahn School of Medicine at Mount Sinai, Stony Brook University, Cold Spring Harbor Laboratory, and other institutions argue that research into infection-associated chronic illnesses suffers from recurring methodological problems. Chief among these is the failure to confirm that participants actually carry the relevant pathogen.

Lyme disease illustrates the issue. Of the roughly 476,000 Americans diagnosed each year, up to 20% develop post-treatment Lyme disease syndrome, marked by persistent cognitive impairment, fatigue, and pain. For decades, researchers have searched for causes and cures, but many studies enrolled anyone with Lyme antibodies or a bull's-eye rash rather than documenting Borrelia burgdorferi, the bacterium responsible for the disease. Because Lone Star tick bites, drug reactions, and other conditions can produce identical rashes—and antibody tests reveal only past exposure rather than active infection—study populations may include people with entirely different diseases.

"How can studies produce concrete conclusions about Lyme when you don't know if patients really had Lyme disease or if they had a mimicking condition?" asked corresponding author Steven Schutzer. The authors also flagged weaknesses in control groups and sample handling. 

Long COVID research, involving an estimated 9 million Americans, faces similar challenges, particularly the tendency to group patients with possibly different underlying mechanisms into a single population. Studies of myalgic encephalomyelitis/chronic fatigue syndrome prove even harder, since no causative pathogen has been identified. Still, the authors note that multiple sclerosis research demonstrates progress is possible, having produced FDA-approved treatments through rigorous design.

"The framework we advocate is a major step forward since it provides rigorous and well-thought-out guidelines for every aspect of conducting clinical trials in this patient population," said coauthor Avindra Nath.