Prolonged Symptoms after COVID-19 in Japan: A Nationwide Survey of the Symptoms and Their Impact on Patients’ Quality of Life

Background: Clinical details of long COVID are still not well understood because of potential confounding with a wide range of pre-existing comorbidities. Methods: The present study used datasets from a nationwide, cross-sectional, online survey. We determined which prolonged symptoms were more likely to be associated with post-COVID condition after adjusting for a wide range of comorbidities and baseline characteristics. This study also used the EuroQol 5 Dimension 5 Level (EQ-5D-5L) and Somatic Symptom Scale-8 to assess health-related quality of life (QOL) and somatic symptoms in individuals with a previous history of COVID-19, defined as the diagnosis of COVID-19 made at least 2 months prior to the online survey. Results: In total, 19,784 respondents were included for analysis; of these, 2397 (12.1%) had a previous history of COVID-19. The absolute difference of adjusted prevalence of symptoms attributed to prolonged symptoms after COVID-19 ranged from -0.4% to +2.0%. Headache (adjusted odds ratio [aOR]: 1.22; 95% confidence interval [95% CI]:1.07-1.39), chest discomfort (aOR:1.34, 95% CI:1.01-1.77), dysgeusia (aOR: 2.05, 95% CI: 1.39-3.04), and dysosmia (aOR: 1.96, 95% CI: 1.35-2.84) were independently associated with a previous history of COVID-19. Individuals with a previous history of COVID-19 had lower health-related QOL scores. Conclusions: After adjusting for potential comorbidities and confounders, clinical symptoms, such as headache, chest discomfort, dysgeusia, and dysosmia, were found to be independently associated with a previous history of COVID-19, which was diagnosed 2 or more months previously. These protracted symptoms might have impacted QOL and the overall somatic symptom burden in subjects with a previous history of COVID-19.