Physical and cognitive impact following SARS-CoV-2 infection in a large population-based case-control study
Authors: Holm Hilma , Ivarsdottir Erna V. , Olafsdottir Thorhildur , Thorolfsdottir Rosa , Eythorsson Elias , Norland Kristjan , Gisladottir Rosa , Jonsdottir Gudrun , Unnsteinsdottir Unnur , Sveinsdottir Kristin E. , Jonsson Benedikt A. , Andresdottir Margret , Arnar David O. , Arnthorsson Asgeir O. , Birgisdottir Kolbrún , Bjarnadottir Kristbjorg , Bjarnadottir Solveig , Bjornsdottir Gyda , Einarsson Gudmundur , Eiriksdottir Berglind , Gardarsdottir Elisabet Eir , Gislason Thorarinn , Gottfredsson Magnus , Gudmundsdottir Steinunn , Gudmundsson Julius , Gunnarsdottir Kristbjorg , Helgadottir Anna , Helgason Dadi , Hinriksdottir Ingibjorg , Ingvarsson Ragnar F. , Jonasdottir Sigga S. , Jonsdottir Ingileif , Karlsdottir Tekla H. , Kristinsdottir Anna M. , Kristinsson Sigurdur Yngvi , Kristjansdottir Steinunn , Love Thorvardur J. , Ludviksdottir Dora , Masson Gisli , Norddahl Gudmundur , Olafsdottir Thorunn , Olafsson Isleifur , Rafnar Thorunn , Runolfsdottir Hrafnhildur L. , Saemundsdottir Jona , Sigurbjornsson Svanur , Sigurdardottir Kristin , Sigurdsson Engilbert , Sigurdsson Martin I. , Sigurdsson Emil L. , Steinthorsdottir Valgerdur , Sveinbjornsson Gardar , Thorarensen Emil A. , Thorbjornsson Bjarni , Thorsteinsdottir Brynja , Tragante Vinicius , Ulfarsson Magnus O. , Stefansson Hreinn , Gislason Thorsteinn , Kristjansson Mar , Palsson Runolfur , Sulem Patrick , Thorsteinsdottir Unnur , Thorgeirsson Gudmundur , Gudbjartsson Daniel F. , Stefansson Kari 
Published: July 2023

Abstract
Background
Persistent symptoms are common after SARS-CoV-2 infection but correlation with objective measures is unclear.

Methods
We invited all 3098 adults who tested SARS-CoV-2 positive in Iceland before October 2020 to the deCODE Health Study. We compared multiple symptoms and physical measures between 1706 Icelanders with confirmed prior infection (cases) who participated, and 619 contemporary and 13,779 historical controls. Cases participated in the study 5–18 months after infection.

Results
Here we report that 41 of 88 symptoms are associated with prior infection, most significantly disturbed smell and taste, memory disturbance, and dyspnea. Measured objectively, cases had poorer smell and taste results, less grip strength, and poorer memory recall. Differences in grip strength and memory recall were small. No other objective measure associated with prior infection including heart rate, blood pressure, postural orthostatic tachycardia, oxygen saturation, exercise tolerance, hearing, and traditional inflammatory, cardiac, liver, and kidney blood biomarkers. There was no evidence of more anxiety or depression among cases. We estimate the prevalence of long Covid to be 7% at a median of 8 months after infection.

Conclusions
We confirm that diverse symptoms are common months after SARS-CoV-2 infection but find few differences between cases and controls in objective parameters measured. These discrepancies between symptoms and physical measures suggest a more complicated contribution to symptoms related to prior infection than is captured with conventional tests. Traditional clinical assessment is not expected to be particularly informative in relating symptoms to a past SARS-CoV-2 infection.