Clinical-functional vulnerability, but not oxidative stress markers, is associated with self-perceived post-COVID sequelae in community-dwelling older adults: a six-month longitudinal study.

Oxidative stress has been proposed as a central mechanism in post-COVID condition pathophysiology; however, its relationship with subjective symptom burden in older adults remains uncertain. This longitudinal study investigated whether oxidative stress markers are associated with self-perceived postCOVID sequelae in community-dwelling older adults over six months. Fifty-five individuals with confirmed SARS-CoV-2 infection were included, and 49 had complete laboratory data. Hematological, biochemical, and oxidative stress markersincluding thiobarbituric acid reactive substances (TBARS), protein carbonylation, and DCFH-DA derived reactive oxygen species (ROS)were assessed at baseline and six months. Self-perceived sequelae were measured using a Likert scale, and clinical-functional vulnerability was evaluated with the IVCF-20. Over time, TBARS levels increased and protein carbonylation decreased, while ROS levels remained stable. Some biochemical markers showed significant variation, although mean values remained within reference ranges. No significant associations were observed between oxidative stress markers and self-perceived post-COVID impact. In contrast, greater clinical-functional vulnerability, particularly memory-related domains, was significantly associated with increased perceived burden. Most oxidative changes occurred independently of classical risk factors such as age, sex, diabetes, and obesity. These findings suggest that subjective post-COVID impact in older adults is more strongly related to cognitive and functional vulnerability than to persistent systemic oxidative imbalance.