Introduction
Dyspnea is a commonly described symptom in various chronic and acute conditions. Despite its frequency, relatively little is known about the prevalence and assessment of dyspnea in general populations. The aims of this review were: 1) to estimate the prevalence of dyspnea in general adult populations; 2) to identify associated factors; and 3) to identify used methods for dyspnea assessment.

Methods
A systematic literature search was conducted using MEDLINE/PubMed, Embase, CINAHL and JAMA network. Records were screened by two independent reviewers and quality was assessed by using the Joanna Briggs Institute checklist for risk of bias in prevalence studies. Multi-level meta-analysis was performed to estimate pooled prevalence. The protocol was registered on PROSPERO (CRD42021275499).

Results
Twenty original articles, all from studies in high-income countries, met the criteria for inclusion. Overall, their quality was good. Pooled prevalence of dyspnea in general adult populations based on 11 studies was 10% (95% CI 7, 15), but heterogeneity across studies was high. The most frequently reported risk factors were increasing age, female sex, higher BMI and respiratory or cardiac disease. The MRC or the modified MRC scale was the most used tool to assess dyspnea in general populations.

Conclusions
Dyspnea is a common symptom in adults in high-income countries. However, the high heterogeneity across studies and the lack of data from low- and middle-income countries limit the generalizability of our findings. Therefore, more research is needed to unveil the prevalence of dyspnea and its main risk factors in general populations around the world.