Greater Role of Cognitive Impairment Over Fatigue in Post-COVID-19 Quality of Life: A Post-Hoc Analysis of a Randomized Controlled Trial.

Background: Post COVID-19 Condition (PCC) is a common and debilitating condition with significant reports of fatigue and psychosocial impairment globally. The extent to which cognitive symptoms and fatigue contribute to reduced quality of life in affected individuals remains clear.

Methods: This is a post-hoc analysis of a randomized, double-blind, placebo-controlled clinical trial that evaluated the effect of vortioxetine on cognitive function in adults with PCC. The post-hoc analysis herein aimed to determine the overall effect of baseline cognitive function [as measured by the Digit Symbol Substitution Test (DSST)] and baseline fatigue severity [as measured by the Fatigue Severity Scale (FSS)] on baseline health-related quality of life (HRQoL) [as measured by the 5-item World Health Organisation Well-Being Index (WHO-5)].

Results: A total of 200 participants were enrolled in the primary trial. Due to missing baseline data, our statistical analysis included baseline measures of 147 individuals. Our generalized linear model analysis revealed a significant positive correlation between DSST-measured objective cognitive function and self-reported WHO-5-measured HRQoL (β = 0.069, 95% CI [0.006, 0.131], = 0.032). In contrast, our analysis revealed a significant negative correlation between FSS and WHO-5 scores (β = -0.016, 95% CI [-0.021, -0.011], < 0.001). The beta-coefficient ratio (β / β = 0.069 / 0.016) is calculated as 4.313.

Conclusions: Overall, we observed that increased cognitive function was associated with increased HRQoL at baseline in adults with PCC. Moreover, we observed that increased severity of fatigue symptoms was associated with decreased HRQoL at baseline in adults with PCC. Furthermore, we observed that an improvement in cognitive function would have a four-fold greater impact on HRQoL than the effect generated by improvement in fatigue.