Body size measures and risk of venous thromboembolism: protocol for a systematic review and meta-analysis

INTRODUCTION: Obesity is significant risk factor for venous thromboembolism (VTE); however, the related mechanisms remain unclear. Previous studies have suggested that this might be related to physical factors including anthropometric measures. We intend to conduct a systematic review and meta-analysis of prospective studies to summarise the extant literature on the associations between a set of seven measures of body size and the risk of VTE. METHODS AND ANALYSIS: The current systematic review will include prospective cohort studies assessing the association between seven measures of body size (height, weight, body mass index, waist and hip circumferences, waist-to-hip ratio, waist-to-height ratio) and the risk of VTE. We will conduct comprehensive searches of MEDLINE and Excerpta Medica Database (EMBASE) for articles published from inception through 31 August 2017, without any language restriction. Two investigators will independently screen, select studies and perform data extraction and risk of bias assessment, with discrepancies resolved by a third investigator. For each body size measure, study-specific relative risks will be pooled using random effects meta-analysis models. Statistical heterogeneity will be assessed using Cochran’s Q statistic, H and the I(2) statistics. Sources of heterogeneity will be investigated using subgroup and meta-regression analyses as deemed appropriate. Publication bias will be assessed with funnel plots supplemented by Egger’s test. ETHICS AND DISSEMINATION: This systematic review will use data from published literature; therefore, ethical approval is not required. We expect our findings to supplement previous epidemiological studies by providing an updated and comprehensive synthesis of the available evidence on the association between body size measures and risk of VTE in the general population. Findings will be published in peer-reviewed journal and presented at scientific meetings. PROSPERO REGISTRATION NUMBER: CD CRD42017071996.