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.
ImportanceAtrial fibrillation (AF) is the most common, chronic, cardiac arrythmia in older US adults. It is not known whether AF is independently associated with increased risk of retinal stroke (central retinal artery occlusion), a subtype of ischemic stroke that causes severely disabling visual loss in most cases and is a harbinger of further vascular events.ObjectiveTo determine whether there is an association between AF and retinal stroke.Design, Setting, and ParticipantsThis retrospective cohort study was performed between July 2023 and May 2024 using computerized inpatient, outpatient, emergency department, and skilled nursing facility claims files for a 5% sample of US fee-for-service Medicare beneficiaries aged 66 years and older between 2000 and 2020. Follow-up ended at death, conclusion of fee-for-service Medicare coverage, end of the study period, or loss to follow-up of 85% of the study cohort.ExposureAF, based on validated International Classification of Diseases, Ninth Revision, Clinical Modification and International Statistical Classification of Diseases, Tenth Revision, Clinical Modification diagnosis codes.Main Outcomes and MeasuresThe primary end point was incident retinal stroke in the primary diagnostic position of a single claim in any venue of care. Secondary end points included retinal stroke in any position of a single claim, 1 positive control end point (cerebral ischemic stroke), and 4 negative control end points (central retinal vein occlusion, urinary tract infection, humeral fracture, and cataract). Unadjusted and adjusted hazard ratios (HRs) and rate differences were computed across matched and overlap-weighted cohorts with and without AF (defined as 1 inpatient claim or 2 outpatient claims within a 365-day period).ResultsIn total, 1 090 144 patients (591 400 female [54.3%]; mean [SD] age, 76.92 [7.09] years) were included in the study; 545 072 patients had AF and 545 072 were matched controls. The median (IQR) follow-up was 45 (18 to 90) months. In total, 1333 patients with AF (rate, 0.55 per 1000 person-years) and 1082 AF-free matched controls (rate, 0.50 per 1000 person-years) experienced retinal stroke. The cause-specific, adjusted HR of retinal stroke after overlap weighting was 1.14 (95% CI, 1.02 to 1.28; adjusted rate difference, 0.05 [95% CI, −0.01 to 0.11]). AF was associated with cerebral ischemic stroke (adjusted HR, 1.73 [95% CI, 1.69 to 1.76]; adjusted rate difference, 10.11 [95% CI, 9.72 to 10.49]). Of 4 prespecified negative control end points, AF was not associated with central retinal vein occlusion but was associated with urinary tract infection, cataract, and humeral fracture.Conclusions and RelevanceIn this cohort study of Medicare beneficiaries aged 66 years and older, AF was independently associated with retinal stroke. The magnitude of the association was small, and a contribution from residual, unmeasured confounding could not be excluded.