The Relationship between Military Combat and Cardiovascular Risk: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES: Cardiovascular disease (CVD) is a leading cause of death among military veterans with several reports suggesting a link between combat and related traumatic injury (TI) to an increased CVD risk. The aim of this paper is to conduct a widespread systematic review and meta-analysis of the relationship between military combat ± TI to CVD and its associated risk factors. METHODS: PubMed, EmbaseProQuest, Cinahl databases and Cochrane Reviews were examined for all published observational studies (any language) reporting on CVD risk and outcomes, following military combat exposure ± TI versus a comparative nonexposed control population. Two investigators independently extracted data. Data quality was rated and rated using the 20-item AXIS Critical Appraisal Tool. The risk of bias (ROB using the ROBANS 6 item tool) and strength of evidence (SOE) were also critically appraised. RESULTS: From 4499 citations, 26 studies (14 cross sectional and 12 cohort; 78–100% male) met the inclusion criteria. The follow up period ranged from 1 to 43.6 years with a sample size ranging from 19 to 621901 participants in the combat group. Combat-related TI was associated with a significantly increased risk for CVD (RR 1.80: 95% CI 1.24–2.62; I(2) = 59%, p = 0.002) and coronary heart disease (CHD)-related death (risk ratio 1.57: 95% CI 1.35–1.83; I(2) = 0%, p = 0.77: p < 0.0001), although the SOE was low. Military combat (without TI) was linked to a marginal, yet significantly lower pooled risk (low SOE) of cardiovascular death in the active combat versus control population (RR 0.90: CI 0.83–0.98; I(2) = 47%, p = 0.02). There was insufficient evidence linking combat ± TI to any other cardiovascular outcomes or risk factors. CONCLUSION: There is low SOE to support a link between combat-related TI and both cardiovascular and CHD-related mortality. There is insufficient evidence to support a positive association between military combat ± any other adverse cardiovascular outcomes or risk factors. Data from well conducted prospective cohort studies following combat are needed.