From the Guidelines
Asian populations have a significantly higher incidence of subarachnoid hemorrhage (SAH) compared to other ethnic groups, with a risk approximately 1.6 times higher than in Western populations, as supported by studies such as 1. This increased risk is attributed to a combination of genetic and environmental factors. Genetic factors, including certain genetic variants more common in Asian populations, play a significant role in affecting blood vessel integrity and aneurysm formation 1. Environmental factors, such as higher rates of smoking and hypertension in some Asian countries, also contribute to the increased risk, as these are major risk factors for SAH 1. Additionally, dietary patterns, particularly high sodium intake common in many Asian cuisines, may exacerbate hypertension and increase the risk of SAH. Key preventive measures include:
- Blood pressure control with a target below 130/80 mmHg using antihypertensive medications such as ACE inhibitors, ARBs, or calcium channel blockers
- Smoking cessation
- Moderate alcohol consumption
- Dietary sodium reduction Regular screening with non-invasive imaging like MRA or CTA may be beneficial for high-risk individuals, especially those with a family history of SAH or aneurysms 1. It is essential to prioritize these preventive measures to reduce the risk of SAH in Asian populations, given their higher susceptibility. The importance of genetic predisposition is highlighted by studies showing that individuals of Japanese or Finnish descent have a higher risk of aneurysm rupture, with a relative risk of 3.4, as reported in 1. Therefore, a comprehensive approach addressing both genetic and environmental factors is crucial for reducing the incidence of SAH in Asian populations.
From the Research
Asian Proclivity for Subarachnoid Hemorrhage
- The incidence of subarachnoid hemorrhage (SAH) is higher in Japan compared to other countries, with a higher rupture rate of unruptured cerebral aneurysms 2.
- A study found that unruptured cerebral aneurysms are 2.8 times more likely to rupture in Japanese individuals than in Western individuals, resulting in the highest incidence of SAH in the world 2.
- The characteristics of cerebral aneurysms in Japan differ from those in other countries, with a higher incidence of unruptured cerebral aneurysm detected by brain check-up screening, and superior outcome after SAH based on meta-analysis 2.
- A retrospective review of patients with aneurysmal subarachnoid hemorrhage (aSAH) found that Asian patients had a higher in-hospital mortality rate (14.0%) compared to White patients, although the difference was not significant after adjusting for covariates 3.
- The study also found that Hispanic patients had a higher risk of developing cerebral infarction and symptomatic vasospasm, and worse functional outcomes at discharge, compared to White patients 3.
Risk Factors for Subarachnoid Hemorrhage
- Current smoking, hypertension, and excessive alcohol intake are significant risk factors for SAH, with pooled relative risks of 2.2.5, and 2.1, respectively 4.
- Nonwhite ethnicity is also a risk factor for SAH, although the association is less robust, with a pooled relative risk of 1.8 4.
- Hypertension is a major risk factor for the development and rupture of cerebral aneurysms, with an exposure odds ratio of 6.8 5.
Management and Outcomes of Subarachnoid Hemorrhage
- Prompt aneurysm treatment is crucial to minimize the risk of rebleeding, and endovascular occlusion of the aneurysm with coils has been shown to be associated with better short- and long-term outcomes than surgical clipping in select patients 6.
- Delayed cerebral vasospasm is a leading cause of brain damage after aneurysm treatment, and hemodynamic augmentation therapy remains the mainstay of medical treatment, although various agents are being tested to prevent or ameliorate vasospasm 6.