RESUMEN
OBJECTIVE: To analyse the characteristics of normal infrarenal aortic diameter (AD) in the general worldwide population, to examine changes over time, and to investigate geographical differences. DATA SOURCES: PubMed, Cochrane Library, and Web of Science. REVIEW METHODS: This was a systematic review and meta-analysis of studies published up to October 2020 describing infrarenal AD measured by ultrasound in the general adult population. The study was conducted in accordance with the PRISMA statement and placed no restrictions on geographical location or year of publication. Studies of individuals pre-selected for certain diseases or risk factors and opportunistic screening were excluded. A random effects model was used to estimate pooled mean AD, and meta-regression analysis was used to study the effects of determinants of AD. RESULTS: Thirty-two studies were included, reporting data for 941 144 individuals (98% were men). The pooled mean AD was 19.4 mm (95% confidence interval [CI] 18.8 - 20.1), being 20.1 mm (95% CI 19.4 - 20.8) in men and 17.8 mm (95% CI 16.5 - 19.1) in women (p < .001). Outer edge to outer edge (OTO) caliper placement method (p = .015) and body surface area (BSA; p = .010) were significantly associated with larger AD. In men, the largest mean AD was observed in Oceania (p < .001) and the smallest in Asia (p < .020). As none of the studies collected data between 2002 and 2007, the studies were divided into two periods: 2001 and before, and 2008 and after. All recent studies were European, with the diameters being significantly smaller (p = .003) in the latter period (18.3 mm [95% CI 17.5 - 19.1] vs. 20.7 mm [95% CI 19.1 - 22.3]). In the meta-regression models, the reduction in AD over time remained significant after adjustment for potential effect modifiers such as sex, age, geographical area, body size, cardiovascular risk factors, and ultrasound method. CONCLUSION: Mean infrarenal AD in older European adults has decreased significantly in recent decades. Male sex, BSA, and OTO ultrasound measurement method are associated with larger AD, and geographical differences were observed in men.