To the Editor—In their systematic review and meta-analysis on the global prevalence of long coronavirus disease 2019 (COVID-19), Chen et al report that a significant share of patients with COVID-19 suffer from sequelae of acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection [1]. The authors performed a database search in PubMed, Embase, and iSearch and included 50 studies comprising hospitalized and nonhospitalized patients from the Americas, Europe, and Asia, of which 41 studies were meta-analyzed. The estimated pooled prevalence of a post–COVID-19 condition was 0.43 (95% confidence interval, .39–.46) [1].
Concerning a post–COVID-19 condition, or long COVID, and their global burden of disease, we think it is important to bear in mind that many studies (including our own [2], which was in the meta-analysis) assess long COVID symptoms via self-report/questionnaires. Self-reported outcomes do not necessarily match clinical reports that are based on physical and/or technical examinations. Thus, there is a difference between functional impairment based on objective medical findings and self-estimation, giving rise to potential detection bias, as the authors briefly mention in the supplement. Moreover, possible bias through elevated media attention, resulting in potentially altered response behavior, must be considered.
Making causal links between nonspecific symptoms, such as dizziness, headache, or fatigue, to SARS-CoV-2 or acute COVID-19 remains challenging [3]. Furthermore, precise pathophysiological mechanisms underlying specific long COVID symptoms have not been fully elucidated [4, 5]. Fatigue, for example, is associated with several chronic conditions and its prevalence in the population is estimated to be in the same range as found in SARS-CoV-2 cases in the present meta-analysis [6]. With regard to the World Health Organization definition, a post–COVID-19 condition may represent a diagnosis per exclusion in many cases [7]. Nonetheless, even if the prevalence of long COVID was overestimated in the underlying studies, COVID-19 sequelae pose a considerable burden on health, social insurance systems, and economies worldwide given the high attack rate of SARS-CoV-2 [8].
Source: Lampl BMJ, Leitzmann MF, Salzberger B. Prevalence of Post-COVID-19 Conditions Depends on the Method of Assessment. J Infect Dis. 2023 Jan 11;227(2):306. doi: 10.1093/infdis/jiac467. PMID: 36546758. https://academic.oup.com/jid/article/227/2/306/6853665 (Full text)