Global Burden Of Nontraumatic Subarachnoid Hemorrhage

Key Takeaways

• Nontraumatic subarachnoid hemorrhage carried a large global burden in 2021, with lower age-standardized incidence, prevalence, mortality, and disability-adjusted life-year rates than in 1990 even as absolute incident and prevalent case counts rose.
• Burden varied across regions, SDI strata, age groups, and sex, with the highest age-standardized estimates in Latin America and the Caribbean and elevated estimates in Oceania and high-income Asia Pacific.
• Most subarachnoid hemorrhage-related disability-adjusted life-years were attributed to 14 modeled risk factors, led by high systolic blood pressure and smoking.

An estimated 10.64 million disability-adjusted life-years were linked to nontraumatic subarachnoid hemorrhage worldwide in 2021 in a JAMA Neurology analysis. The cross-sectional Global Burden of Disease 2021 investigation covered 204 countries and territories and tracked burden patterns from 1990 through 2021. Age-standardized burden rates declined over time, but the worldwide burden remained large and unevenly distributed across regions and populations.

This original investigation assessed nontraumatic subarachnoid hemorrhage across all ages and excluded recurrent events and secondary hemorrhage caused by trauma. It examined estimates from 1990 through 2021 across 204 countries and territories and evaluated 14 modifiable risk factors. In 2021, it estimated 0.7 million incident cases, 7.85 million prevalent cases, 0.35 million deaths, and 10.64 million disability-adjusted life-years worldwide. Age-standardized rates per 100,000 were 8.33 for incidence, 92.17 for prevalence, 4.18 for mortality, and 125.20 for disability-adjusted life-years, underscoring the scale of the worldwide burden.

From 1990 to 2021, age-standardized incidence declined 28.8%, prevalence 16.1%, mortality 56.1%, and disability-adjusted life-year rate 54.6%. Over the same period, incident cases rose from 0.5 million to 0.7 million, a 37.1% increase, and prevalent cases rose from 4.9 million to 7.9 million, a 60.2% increase. Globally, subarachnoid hemorrhage ranked 36th among 300 level 4 causes of death and 59th among 300 level 4 causes of disability-adjusted life-years. Even with lower age-standardized rates, subarachnoid hemorrhage remained among the leading global causes of death and disability-adjusted life-years.

Burden varied markedly by location and population subgroup in 2021. Latin America and the Caribbean had the highest age-standardized incidence, prevalence, mortality, and disability-adjusted life-year rates among super regions, while Oceania and high-income Asia Pacific also ranked high. High-SDI regions had the highest prevalence but the lowest mortality and disability-adjusted life-year rates, whereas low-middle and middle SDI regions had the highest incidence, mortality, and disability-adjusted life-year rates. Prevalence was higher in females, other age-standardized burden measures were higher in males, and rates increased with age across reported groups.

In 2021, 71.6% of worldwide subarachnoid hemorrhage-related disability-adjusted life-years were attributed to the 14 modeled risk factors. The largest individual population attributable fractions were 51.6% for high systolic blood pressure, 14.4% for smoking, and 14.2% for ambient particulate matter pollution. Combined attribution was 77.3% in low-SDI settings and 64.3% in high-SDI settings, while household air pollution accounted for 35.8% and less than 0.1%, respectively. Metabolic risks formed the largest risk cluster, and these were modeled comparative-risk estimates rather than causal trial evidence. The investigators also noted underestimation in data-sparse low-SDI settings, especially Sub-Saharan Africa, and cautioned against applying the findings specifically to aneurysmal subarachnoid hemorrhage.