Antibody Profiles Offer Insights into Long COVID Cognitive Symptoms, Study Finds
核心洞察
A study of 275 Omicron-era long COVID (搜索) patients found that lower SARS-CoV-2 spike antibody (搜索) levels were significantly associated with memory impairment, a hallmark of brain fog.
Nucleocapsid antibody levels reflected infection-related factors such as disease severity and time since infection, declining approximately 0.34% per day in unvaccinated patients.
Higher spike antibody levels correlated with better self-reported quality of life, suggesting antibody profiles may help predict neurological complications in long COVID (搜索).
A research team led by Professor Fumio Otsuka from Okayama University Graduate School of Medicine has identified distinct antibody profiles that may help clinicians objectively assess cognitive symptoms in patients with long COVID (搜索) (LC). The findings, published in the British Journal of Biomedical Science on April 22, 2026, suggest that declining SARS-CoV-2 spike (S) antibody levels could signal a greater risk of neurological complications, particularly memory impairment.
The study analyzed data from 275 patients diagnosed with Omicron variant-related LC who attended a specialized post-COVID outpatient clinic between July 2023 and November 2024. Researchers measured antibody levels against both the SARS-CoV-2 spike and nucleocapsid (N) proteins and compared these with vaccination history, acute infection severity, symptom profiles, laboratory findings, and quality of life assessments.
Spike and nucleocapsid antibodies reveal distinct clinical patterns
The team found that S-antibody levels were strongly associated with the number of vaccine doses received, while N-antibody levels reflected infection-related factors such as disease severity and the time elapsed since infection. Among unvaccinated patients, N-antibody levels steadily declined over time, decreasing by approximately 0.34% per day after infection. The findings also showed that women tended to have higher N-antibody levels than men.
N-antibody levels correlated positively with lymphocyte counts and immunoglobulin levels, further supporting their role as indicators of immune activity following infection. These insights may help clinicians interpret antibody test results more effectively in patients whose acute infection history is incomplete or poorly documented.
Cognitive symptoms linked to lower spike antibody levels
The most clinically significant observation involved cognitive symptoms. Patients experiencing memory impairment—a common manifestation of brain fog—had significantly lower S-antibody levels than those without memory problems. Higher S-antibody levels were also associated with better self-reported quality of life.
Although antibody measurements alone were insufficient to fully predict cognitive symptoms, the results suggest that declining S-antibody levels may indicate a greater risk of neurological complications in LC.
"Objective biomarkers for LC remain limited, making patient evaluation particularly challenging. In the treatment of post-COVID-19 symptoms, viral antibody titers may help predict the history of COVID-19 infection during the Omicron phase and may aid in the prognosis of post-COVID-19 symptoms, which are difficult to objectively determine," said Prof. Otsuka.
Toward personalized care for long COVID (搜索)
The study underscores the persistent challenge of long COVID (搜索), which continues to affect millions worldwide with symptoms including fatigue, headaches, sleep disturbances, breathing difficulties, and cognitive problems. Many LC symptoms remain subjective and difficult to quantify using conventional medical tests, making the search for reliable biological markers a priority.
"Our findings suggest that antibody profiles may provide useful information about infection history, immune responses, and symptom patterns, especially in patients experiencing cognitive difficulties. In future, we hope to combine viral antibody titers with clinical symptoms and other laboratory data to improve diagnosis and treatment strategies for LC," Prof. Otsuka added.
The research indicates that SARS-CoV-2 antibody profiles may offer a practical tool for understanding LC during the Omicron era. By providing objective information about prior infection, immune responses, and cognitive symptoms, antibody testing could contribute to more personalized care for patients living with persistent post-COVID conditions and support future efforts to develop evidence-based management strategies.