¹Federal Institute for Occupational Safety and Health, Berlin, Germany
²Institute of Occupational and Social Medicine and Health Services Research, University of Tübingen and University Hospital Tübingen, Tübingen, Germany

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Introduction: More than half of all employees in Germany often work in a standing position. The occurrence of varicose veins (VV) of the lower extremities in populations exposed to prolonged standing has been reported in several studies, however, the causative duration of exposure has not yet been quantified. Therefore, the main objective of this systematic review is to evaluate the risk of developing VV of the lower extremities in workers who are exposed to prolonged occupational standing compared to populations not exposed to prolonged occupational standing. Our secondary objectives are to describe the exposure risk relationship between the duration of occupational standing and the development of VV as well as to gather information on the prevalence and incidence of VV in different populations.

Methods: The protocol was preregistered in PROSPERO (CRD42023482556). In November 2023, we performed a systematic literature search in the databases MEDLINE, EMBASE, CINAHL, Web of Science and EBSCO Open Dissertation. Epidemiological observational studies and (randomized) controlled trials were eligible without restrictions on publication date, language or country. We included studies providing measures of occurrence or association for prolonged occupational standing and VV in workers and retirees. All workplaces, occupations and occupational tasks that involved standing for several hours a day or week were eligible, irrespective of any additional exposures. As outcome, we accepted a diagnosis (e.g., ICD code, duplex sonography, CEAP classification), clinical symptoms (e.g., oedema, eczema) or subjective information by the patient on complaints (e.g., pain, itching) related to VV. After completing the data extraction and Risk of Bias (RoB) assessment following the approach of Ijaz, we will perform a quantitative synthesis of studies that contain sufficient information and that arejudged as being clinically (population characteristics) and methodologically (study design, outcome measurement tools, RoB) homogeneous enough. If more than one study provides usable data in any comparison, we will perform a meta-analysis. Quality of evidence will be rated using the ‘Grading of Recommendations Assessment, Development, and Evaluation’ (GRADE) method.

Results: After deduplication, 10 044 records were identified of which 74 studies conducted on six continents were included. Another 31 additional studies were found through forward and backward citation tracking. Data extraction and RoB assessment are ongoing. 34 studies have been processed so far, all of which we rated with a high RoB due to strong limitations in exposure assessment and almost all study designs were cross-sectional, which prevents from establishing the temporal course of exposure in relation to the outcome.

Discussion: We identified a large number of relevant studies which vary greatly in their definition and quantification of standing exposure. Furthermore, only a minority of the studies provide measures of association or information on the response. If the extracted data is homogeneous enough, we will conduct a meta-analysis to quantify the risk of occupational standing causing VV and to describe the exposure outcome relationship.