Acute COVID-19 severity and impaired cognitive function up to 32 months after diagnosis: an observational study.
Magnúsdóttir I., Nygaard AB., Hoffart A., Murphy G., Kõiv K., Barker MM., Lovik A., Unnarsdóttir AB., Kähler AK., Hauksdóttir A., Thordardottir EB., Eyþórsson E., Gísladóttir EU., Joyce EE., Frans EM., Tómasson G., Hjördísar Jónsdóttir HL., Rúnarsdóttir H., Harðardóttir H., Dahl JA., Jakobsdóttir J., Kalleberg KT., Ásbjörnsdóttir KH., Ellingjord-Dale M., Istre MS., Landrø NI., Shen Q., Bø R., Mägi R., Pálsson R., Brunvoll SH., Johnson SU., Søraas A., Fang F., Lehto K., Ebrahimi OV., Aspelund T., Valdimarsdóttir UA.
BACKGROUND: Cognitive dysfunction ("brain fog") is a commonly reported post-COVID-19 symptom. Leveraging data from five general population cohorts across four European countries (Estonia, Iceland, Norway, and Sweden), we assessed long-term prevalence of impaired subjective cognitive function among individuals diagnosed with COVID-19 by acute illness severity. METHODS: The included cohorts consisted of adult participants recruited from March 2020 and followed with self-report measures of cognitive function and past COVID-19 infection (except one cohort consisting of clinically confirmed COVID-19 cases) through February 2023. In a cross-sectional analysis we contrasted the prevalence of impaired cognitive function among individuals with and without a COVID-19 diagnosis, overall and by illness severity up to 32 months post-diagnosis. We adjusted for age, gender, education, relationship status, binge drinking, body mass index, previous psychiatric diagnosis, number of chronic medical conditions, and response period. In a longitudinal analysis, we assessed potential changes in cognitive function scores before and after COVID-19 diagnosis. RESULTS: The study population consisted of 153,841 participants (71% women), with 31,359 (20.4%) reporting a positive COVID-19 test. Overall, a COVID-19 diagnosis was not statistically significantly associated with increased prevalence ratio (PR) of impaired cognitive function (PR 1.30 [95% CI: 0.98-1.71]). Individuals bedridden due to COVID-19 for 1-6 days (PR 1.38 [95% CI 0.96-1.99]) or ≥ 7 days (2.59 [1.55-4.33]) had higher prevalence of impaired cognitive function compared to those never diagnosed, while individuals never bedridden had a lower prevalence to those never diagnosed with COVID-19 (0.89 [0.80-1.00]). These findings were corroborated in the longitudinal analysis where a pre- to post diagnosis decline in cognitive function was observed among individuals bedridden due to COVID-19 (p < 0.0001). CONCLUSIONS: The data indicates that a severe COVID-19 acute illness course is associated with impaired cognitive function up to 18-32 months after COVID-19 diagnosis.