Systematic review of post-COVID condition in Nordic population-based registry studies

Abstract

The long-term effects of COVID-19, known as post-COVID condition (PCC), are still not fully understood. This systematic review synthesizes findings from Nordic registry studies to highlight long-term outcomes after COVID-19 infection. Twenty-two studies, primarily reflecting the pre-omicron and early vaccination phases, reveal increased primary care use for respiratory issues and fatigue in the sub-acute and chronic phases, with PCC incidence estimated below 2% in the general population. Most individuals returned to work within three months post-infection, and the risk of new neurological or mental disorders did not exceed that in patients with other infections. The review demonstrates the value of high-quality Nordic health registries in capturing reliable, population-wide data, though generalizability may be limited to similar healthcare systems. Findings suggest the need for targeted follow-up in patients with severe COVID-19, particularly those requiring intensive care, to manage potential new-onset diseases and guide resource allocation in the pandemic's endemic phase.

Fig. 1. PRISMA flow diagram.

Flow diagram summarises the number of studies excluded at each stage.

Fig. 2. Overview of study timeframes.

Overview of timeframes, times from patient sampling (dark blue) and extended follow-up (light blue) beyond sampling period. Vaccination, virus variants dominating at the respective timeframes are colour coded.