Associations of age, COVID-19 vaccination, and SARS-CoV-2 infection history with health-related quality of life in a community-based longitudinal cohort in Singapore

OBJECTIVES: To assess associations between COVID-19 infection, Long COVID, and health-related quality of life (HR-QoL) in a prospective community serological cohort in Singapore. METHODS: Participants with mild or no infection were followed over 30 months (from August 2020). HR-QoL was measured using the SF-36 at visits 5 and 6 (December 2022-September 2023). Mixed-effects linear regression models examined associations between infection status and SF-36 domains, adjusting for sociodemographic and clinical factors, with age-time since infection interactions. RESULTS: Among 1106 participants (aged 16-94 years), COVID-19 infection was associated with lower HR-QoL, with associations differing by age and time since infection. Participants aged ≥ 65 years had lower physical and mental HR-QoL, including beyond one-year post-infection. Among participants aged 16-64 years, lower HR-QoL was observed during the first 45 days after infection. Long COVID symptoms were associated with lower HR-QoL across multiple domains. Receipt of ≥ 3 mRNA vaccine doses was associated with higher physical and mental HR-QoL scores. CONCLUSIONS: Post-COVID HR-QoL differed substantially by age. Older adults had lower HR-QoL across multiple domains, whereas younger participants showed lower HR-QoL primarily during the early post-infection period. Vaccination and the absence of Long COVID were associated with better HR-QoL outcomes.