COVCOG 2: Cognitive and Memory Deficits in Long COVID: A Second Publication From the COVID and Cognition Study

Abstract

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been often characterized as a respiratory disease. However, it is increasingly being understood as an infection that impacts multiple systems, and many patients report neurological symptoms. Indeed, there is accumulating evidence for neural damage in some individuals, with recent studies suggesting loss of gray matter in multiple regions, particularly in the left hemisphere. There are several mechanisms by which the COVID-19 infection may lead to neurological symptoms and structural and functional changes in the brain, and cognitive problems are one of the most commonly reported symptoms in those experiencing Long COVID - the chronic illness following the COVID-19 infection that affects between 10 and 25% of patients. However, there is yet little research testing cognition in Long COVID. The COVID and Cognition Study is a cross-sectional/longitudinal study aiming to understand cognitive problems in Long COVID. The first paper from the study explored the characteristics of our sample of 181 individuals who had experienced the COVID-19 infection, and 185 who had not, and the factors that predicted ongoing symptoms and self-reported cognitive deficits. In this second paper from the study, we assess this sample on tests of memory, language, and executive function. We hypothesize that performance on "objective" cognitive tests will reflect self-reported cognitive symptoms. We further hypothesize that some symptom profiles may be more predictive of cognitive performance than others, perhaps giving some information about the mechanism. We found a consistent pattern of memory deficits in those that had experienced the COVID-19 infection, with deficits increasing with the severity of self-reported ongoing symptoms. Fatigue/Mixed symptoms during the initial illness and ongoing neurological symptoms were predictive of cognitive performance.

Keywords: COVID-19; Long COVID; cognition; executive functions; language; memory; neurological; symptoms.

FIGURE 1

Cognitive tasks. (A) Wisconsin Card Sorting Test; (B) Pictorial Associative Memory Test; (C) Category Fluency Test; (D) Word List Recognition Memory Test; (E) 2D Mental Rotation Test; (F) Number Counting Test (Attention/Bot Check).

FIGURE 2

Cognitive task factor scores across (A) the No COVID group and the COVID group, and (B) the No COVID group and the three ongoing severity groups. Significant differences were seen between the No COVID group and Ongoing (Mild/Moderate) on Memory [t(87.6) = 2.4, p = 0.018], and between No COVID and Ongoing (Severe) on Memory [t(99.8) = 3.9, p < 0.001] and Category Fluency [t(152) = 3.05, p < 0.003]. After controlling for demographic variables, only the differences in Memory maintained significance (see Supplementary Table 2). Error bars: ± 2 SE.

FIGURE 3

Word List and Associative Memory performance across ongoing symptom groups (A); Category Fluency errors across groups on ongoing symptom severity (B). Error bars: ±2 SE.

FIGURE 4

Symptom factors predicting cognitive task factors. (A) Initial symptoms model (Dermatological) predicting Executive Function Reaction Time; (B) Initial symptoms model (Fatigue/Mixed) predicting Memory; (C) Ongoing symptoms model (Neurological) predicting Executive Function Performance; and (D) Current symptoms model (Neurological) predicting Memory. Note that symptom factors are reversely coded (lower numbers translate to more severe symptoms).

FIGURE 5

(A) Memory factor score for those reporting (or not) current forgetfulness. (B) Memory and Category Fluency factor scores for those reporting (or not) current difficulty concentrating or (C) brain fog. (D) Word List % correct among groups with/without current cognitive symptoms; (E) Category Fluency repetitions among groups with/without current cognitive symptoms. Error bars: ± 2 SE.