Etminan N, et al. - Via searching PubMed, Web of Science, and Embase for studies on subarachnoid hemorrhage (SAH) incidence published between January 1960 and March 2017, researchers evaluated worldwide SAH incidence according to region, age, sex, time period, blood pressure, and smoking prevalence. In this systematic review and meta-analysis of 75 studies involving 8,176 patients, global SAH incidence and its decline showed large regional differences, and demonstrated a decline in blood pressure and smoking prevalence at the same time. Understanding the determinants of regional differences and further reducing the prevalence of blood pressure and smoking may result in a reduced SAH burden.

Methods

• Global blood pressure and smoking prevalence data were obtained from the Noncommunicable Disease Risk Factor and Global Burden of Disease data sets.
• Eligible studies included population-based studies with prospective designs based on predefined criteria representative of the entire study population.
• Two reviewers extracted data independently according PRISMA guidelines.
• The incidence of SAH was calculated per 100,000 person-years and multivariable random-effects binomial regression was used to calculate risk ratios (RRs) including 95% CIs.
• Linear regression was evaluated for the association of SAH incidence with blood pressure and smoking prevalence.
• The main outcomes and measures included incidence of SAH.

Results

• A total of 75 studies were included from 32 countries.
• These studies comprised 8,176 patients with SAH who were studied over 67,746,051 person-years.
• Overall crude SAH incidence throughout the mid-year period was 7.9 per 100,000 person-years; female RR was 1.3.
• Compared with men aged 45 to 54 years, the RR in Japanese women aged > 75 years was 2.5, and in European women aged > 75 years, 1.5.
• Investigators found that global SAH incidence decreased from 10.2 per 100,000 person-years in 1980 to 6.1 in 2010, or by 1.7% annually between 1955 and 2014.
• SAH incidence declined by 40.6% in Europe, 46.2% in Asia, and 14.0% in North America between 1980 and 2010, and increased by 59.1% in Japan.
• Findings revealed that the global incidence of SAH declined with every millimeter of mercury decrease in systolic blood pressure by 7.1% and with every percentage decrease in smoking prevalence by 2.4%.