Long COVID’s Gender-Specific Determinants: 3- and 6-Month Evidence from Thai Females During the Delta and Omicron Waves

Abstract

Objectives: To prospectively identify determinants of Long COVID in Thai females and compare outcomes across the Delta and Omicron periods through structured follow-up assessments at 3 and 6 months post-infection.
Materials and Methods: From May 2021 through June 2022, this prospective cohort study was conducted in Thailand at Thammasat University Hospital and its field hospital. We enrolled 1,484 females aged 18 and older with laboratory-confirmed SARS-CoV-2 infection. Using a standardized questionnaire and trained interviewers to assess Long COVID symptoms, we followed up with participants via telephone interviews at 3- and 6-months post-diagnosis. Multivariable logistic regression was used to identify independent risk factors for Long COVID.
Results: At the 3-month follow-up, 806 participants (54.3%) reported Long COVID symptoms, which persisted in 418 (38.6%) at 6 months. At 3 months, infection during the Omicron-dominant wave (adjusted odds ratio (OR) 1.75, 95% confidence interval (CI): 1.26–2.43) and acute myalgia (adjusted OR 1.52, 95% CI: 1.04–2.22) were significant predictors. At the 6-month follow-up, moderate-to-critical initial illness severity (adjusted OR 2.17, 95% CI: 1.01–4.69) and loss of smell during the acute phase (adjusted OR 1.61, 95% CI: 1.04–2.49) were significant predictors of persistent Long COVID.
Conclusion: In Thai females, determinants for Long COVID shift between 3 and 6 months post-infection. While acute myalgia and the Omicron variant are early predictors, initial illness severity and loss of smell better indicate symptom persistence at 6 months. These findings highlight Long COVID’s dynamic nature and can help identify female patients at higher risk for prolonged symptoms.