Importance:
Nontraumatic subarachnoid hemorrhage (SAH) represents the third
most common stroke type with unique etiologies, risk factors,
diagnostics, and treatments. Nevertheless, epidemiological studies often
cluster SAH with other stroke types leaving its distinct burden
estimates obscure.
Objective:
To estimate the worldwide burden of SAH.
Design, setting, and participants:
Based on the repeated cross-sectional Global Burden of Disease
(GBD) 2021 study, the global burden of SAH in 1990 to 2021 was
estimated. Moreover, the SAH burden was compared with other diseases,
and its associations with 14 individual risk factors were investigated
with available data in the GBD 2021 study. The GBD study included the
burden estimates of nontraumatic SAH among all ages in 204 countries and
territories between 1990 and 2021.
Exposures:
SAH and 14 modifiable risk factors.
Main outcomes and measures:
Absolute numbers and age-standardized rates with 95% uncertainty
intervals (UIs) of SAH incidence, prevalence, mortality, and
disability-adjusted life-years (DALYs) as well as risk factor-specific
population attributable fractions (PAFs).
Results:
In 2021, the global age-standardized SAH incidence was 8.3 (95%
UI, 7.3-9.5), prevalence was 92.2 (95% UI, 84.1-100.6), mortality was
4.2 (95% UI, 3.7-4.8), and DALY rate was 125.2 (95% UI, 110.5-142.6) per
100 000 people. The highest burden estimates were found in Latin
America, the Caribbean, Oceania, and high-income Asia Pacific. Although
the absolute number of SAH cases increased, especially in regions with a
low sociodemographic index, all age-standardized burden rates decreased
between 1990 and 2021: the incidence by 28.8% (95% UI, 25.7%-31.6%),
prevalence by 16.1% (95% UI, 14.8%-17.7%), mortality by 56.1% (95% UI,
40.7%-64.3%), and DALY rate by 54.6% (95% UI, 42.8%-61.9%). Of 300
diseases, SAH ranked as the 36th most common cause of death and 59th
most common cause of DALY in the world. Of all worldwide SAH-related
DALYs, 71.6% (95% UI, 63.8%-78.6%) were associated with the 14 modeled
risk factors of which high systolic blood pressure (population
attributable fraction [PAF] = 51.6%; 95% UI, 38.0%-62.6%) and smoking
(PAF = 14.4%; 95% UI, 12.4%-16.5%) had the highest attribution.
Conclusions and relevance:
Although the global age-standardized burden rates of SAH more than
halved over the last 3 decades, SAH remained one of the most common
cardiovascular and neurological causes of death and disabilities in the
world, with increasing absolute case numbers. These findings suggest
evidence for the potential health benefits of proactive public health
planning and resource allocation toward the prevention of SAH.