Difference in long COVID prevalence due to different definitions and long COVID related risk factors

Abstract Several definitions of long COVID are used in research and practice what challenges epidemiological investigations. Here we present differences in long COVID prevalence accounting for several definitions and concordance between the definitions, as well as the risk factors associated with long COVID. Definitions considered were WHO post-COVID19 condition (PCC) definition with several thresholds (at least low - standard definition, moderate or strong impact on daily activities), NICE1 and NICE2 definitions (reported at least one or at least two symptoms), United States National Centre for Health Statistics, and United Kingdom Office for National Statistics definitions and perceived long COVID. Prevalence of long COVID among French adult population (N = 10 615) in autumn 2022 ranged from 1.2% to 13.4%, conditional of the definition. The concordance between the definitions was at best moderate. Next, on a smaller representative sample of a French adult population (N = 1 813) eight potential risk factors groups for long COVID were assessed in a systematic epidemiological investigation, following a conceptual model. Fifteen factors from seven groups were associated with long COVID including early-defined sociodemographic characteristics, pre-existing chronic conditions, short-term work-related factors, current socioeconomic position, health behaviours, infection-related factors, and perception of COVID-19 severity and long COVID. The likelihood of long COVID was higher for individuals with higher number of diseases and for nineteen out of twenty-six most prevalent dyads and a triad. A more standardized definition would facilitate research and surveillance of long COVID. Furthermore, long COVID should be observed as an interplay of social, medical and contextual factors rather than a mere complication of SARS-COV-2 infection, while patients with multimorbidity may present some of the particularly vulnerable population groups.