Predictors of "brain fog" 1 year after COVID-19 disease

Brain fog has been described up to 1 year after SARS-CoV-2 infection, notwithstanding the underlying mechanisms are still poorly investigated. In this study, we aimed to evaluate the prevalence of cognitive complaints at 1-year follow-up and to identify the factors related to persistent brain fog in COVID-19 patients.

Out of 246 COVID patients, hospitalized from March 1st to May 31st, a sample of 137 patients accepted to be evaluated at 1 year from discharge, through a full clinical, neurological, and psychological examination, including the Montreal Cognitive Assessment (MoCA), impact of event scale-revised (IES-R), Zung self-rating depression scale (SDS), Zung self-rating anxiety scale (SAS), and fatigue severity scale (FSS). Subjects with prior cognitive impairment and/or psychiatric disorders were excluded.

Patients with cognitive disorders exhibited lower MoCA score (22.9 ± 4.3 vs. 26.3 ± 3.1, p = 0.002) and higher IES-R score (33.7 ± 18.5 vs. 26.4 ± 16.3, p = 0.050), SDS score (40.9 ± 6.5 vs. 35.5 ± 8.6, p = 0.004), and fatigue severity scale score (33.6 ± 16.1 vs. 23.7 ± 12.5, p = 0.001), compared to patients without cognitive complaints. Logistic regression showed a significant correlation between brain fog and the self-rating depression scale values (p = 0.020), adjusted for age (p = 0.445), sex (p = 0.178), premorbid Cumulative Illness Rating Scale (CIRS) (p = 0.288), COVID-19 severity (BCRSS) (p = 0.964), education level (p = 0.784) and MoCA score (p = 0.909).

Our study showed depression as the strongest predictor of persistent brain fog, adjusting for demographic and clinical variables. Wider longitudinal studies are warranted to better explain cognitive difficulties after COVID-19.