Worldwide Incidence of Aneurysmal Subarachnoid Hemorrhage According to Region, Time Period, Blood Pressure, and Smoking Prevalence in the Population: A Systematic Review and Meta-analysis

Abstract

Importance: Subarachnoid hemorrhage (SAH) from ruptured intracranial aneurysms is a subset of stroke with high fatality and morbidity. Better understanding of a change in incidence over time and of factors associated with this change could facilitate primary prevention.

Objective: To assess worldwide SAH incidence according to region, age, sex, time period, blood pressure, and smoking prevalence.

Data sources: We searched PubMed, Web of Science, and Embase for studies on SAH incidence published between January 1960 and March 2017. Worldwide blood pressure and smoking prevalence data were extracted from the Noncommunicable Disease Risk Factor and Global Burden of Disease data sets.

Study selection: Population-based studies with prospective designs representative of the entire study population according to predefined criteria.

Data extraction and synthesis: Two reviewers independently extracted data according to PRISMA guidelines. Incidence of SAH was calculated per 100 000 person-years, and risk ratios (RRs) including 95% CIs were calculated with multivariable random-effects binomial regression. The association of SAH incidence with blood pressure and smoking prevalence was assessed with linear regression.

Main outcomes and measures: Incidence of SAH.

Results: A total of 75 studies from 32 countries were included. These studies comprised 8176 patients with SAH were studied over 67 746 051 person-years. Overall crude SAH incidence across all midyears was 7.9 (95% CI, 6.9-9.0) per 100 000 person-years; the RR for women was 1.3 (95% CI, 0.98-1.7). Compared with men aged 45 to 54 years, the RR in Japanese women older than 75 years was 2.5 (95% CI, 1.8-3.4) and in European women older than 75 years was 1.5 (95% CI, 0.9-2.5). Global SAH incidence declined from 10.2 (95% CI, 8.4-12.5) per 100 000 person-years in 1980 to 6.1 (95% CI, 4.9-7.5) in 2010 or by 1.7% (95% CI, 0.6-2.8) annually between 1955 and 2014. Incidence of SAH declined between 1980 and 2010 by 40.6% in Europe, 46.2% in Asia, and 14.0% in North America and increased by 59.1% in Japan. The global SAH incidence declined with every millimeter of mercury decrease in systolic blood pressure by 7.1% (95% CI, 5.8-8.4) and with every percentage decrease in smoking prevalence by 2.4% (95% CI, 1.6-3.3).

Conclusions and relevance: Worldwide SAH incidence and its decline show large regional differences and parallel the decrease in blood pressure and smoking prevalence. Understanding determinants for regional differences and further reducing blood pressure and smoking prevalence may yield a diminished SAH burden.

Conflict of interest statement

Conflict of Interest Disclosures: None reported.

Figures

Figure 1.. Crude Subarachnoid Hemorrhage (SAH) Incidence by Country and Midyear in Europe

Crude SAH incidence per 100 000 person-years with 95% CIs are presented according to country and midyear in Europe.

Figure 2.. Crude Subarachnoid Hemorrhage (SAH) Incidence by Continent, Country, and Midyear

Crude SAH incidence per 100 000 person-years with 95% CIs are presented according to continent, country, and midyear. I2 values are calculated per continent and overall including Europe (Figure 1).

Figure 3.. Association of Time Trends of Blood Pressure and Smoking Prevalence With Subarachnoid Hemorrhage (SAH) Incidence

A, Time trends in SAH incidence in all studies by midyear are presented irrespective of age and sex (black dots). The black line indicates the regression/time trend of SAH incidence with markers for mean estimated incidence for 1980 and 2010. The blue line indicates mean systolic blood pressure levels in studies included in the age-specific and sex-specific analyses, with markers for mean estimated systolic blood pressure levels for 1980 and 2010. B, Time trends in SAH incidence in all studies by midyear are presented irrespective of age and sex (black dots). The black line indicates the regression/time trend of SAH incidence with markers for mean estimated incidence for 1980 and 2010. The red line indicates smoking prevalence in studies included in the age-specific and sex-specific analyses, with markers for smoking prevalence in 1980 and 2010.