Epidemiology of SAH in very short
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Here is a concise summary of the epidemiology of SAH, drawn from Goldman-Cecil Medicine and Bradley & Daroff's Neurology:
Epidemiology of SAH - Summary
Frequency & Stroke Burden
- SAH accounts for ~5% of all strokes and ~25% of hemorrhagic strokes
- Worldwide age-standardized incidence: ~3.3 per 100,000 person-years
- In the US: ~6-11 per 100,000/year (~30,000 cases annually)
- Incidence has not significantly changed over 35 years (improved detection may offset actual decline)
Etiology
- Trauma is the most common cause overall (~70%+ of all SAH)
- Of spontaneous (non-traumatic) SAH: ~80% are due to ruptured saccular (berry) aneurysms at bifurcations of the circle of Willis
- Other causes: peri-mesencephalic SAH, AVM, cerebral amyloid angiopathy, venous sinus thrombosis, vasculitis, coagulopathy
Age & Sex
- Peak incidence: 40-60 years of age
- Women have a higher risk of aneurysm rupture and delayed cerebral ischemia post-SAH
- ~10% of patients with polycystic kidney disease harbor aneurysms
Risk Factors
| Modifiable | Non-modifiable |
|---|---|
| Hypertension (most prominent) | Age |
| Cigarette smoking | Female sex |
| Alcohol abuse | Family history |
| Sympathomimetics (cocaine) | Connective tissue disorders (Ehlers-Danlos type IV, ADPKD) |
| Coarctation of aorta |
Mortality
- ~10% die before reaching hospital; another ~10% die before evaluation
- Overall mortality: 40-50%
- Rebleeding causing coma carries ~50% mortality
Sources: Goldman-Cecil Medicine, 26e; Bradley and Daroff's Neurology in Clinical Practice, 8e
Only epidemiology. In context of nepal too
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https://pmc.ncbi.nlm.nih.gov/articles/PMC8827499
Here is the focused epidemiology of SAH, with Nepal context included:
Epidemiology of SAH
Global Incidence
- ~5-6% of all strokes; ~25% of hemorrhagic strokes
- World age-standardized incidence: ~3.3-10.5 per 100,000 person-years
- Wide geographic variation:
- Finland & Japan: 19-23/100,000 (highest)
- USA: 6-11/100,000 (~30,000 cases/year)
- South/Central America: ~4/100,000
- China: ~2/100,000 (lowest)
- Incidence has been declining since 1990 (EAPC: -1.52%/year globally, GBD 2021)
- Low-to-middle income countries have nearly double the pooled age-adjusted incidence vs. high-income countries
Age & Sex
- Peak: 45-54 years (incidence peaks); 50-60 years (mean presentation)
- Below 50: males > females in incidence
- Above 50: females > males (women 1.24x higher risk of aSAH than men)
- Females have higher risk of aneurysm rupture and delayed cerebral ischemia
Etiology Distribution
- ~80-85% spontaneous SAH = ruptured saccular/berry aneurysm
- Unruptured intracranial aneurysm prevalence in general population: 2-5%
Nepal-Specific Epidemiology
No national stroke registry exists in Nepal. All data are hospital-based (mostly Kathmandu/tertiary centers).
| Parameter | Nepal Data |
|---|---|
| Estimated stroke incidence | ~117/100,000/year (LMIC estimate) |
| Hemorrhagic stroke proportion | ~26-33% of all strokes |
| Mean age of stroke onset | 62.4 years (younger than global average of 68.6) |
| Sex distribution (stroke overall) | 60% male predominance |
| SAH (ruptured aneurysm) | 0.38% prevalence at NINAS (National Institute of Neurological and Allied Sciences), 2016-2018 |
| Mean age of aneurysm rupture (Nepal) | 56.2 years (±13) |
| Sex ratio in SAH (Nepal) | Female predominance: 78% (M:F = 1:3.27) |
| Common SAH distribution | Diffuse (44%) > Sylvian fissure (24%) > Anterior interhemispheric (20%) |
| Fisher Grade at presentation | Grade 4 most common (39%) |
Key features in Nepal:
- Hypertension and smoking are the dominant modifiable risk factors in Nepalese stroke patients (HTN in 30-62%, smoking in 50-60% across studies)
- Younger age of stroke onset likely reflects limited access to stroke care, uncontrolled hypertension, and late presentation
- No thrombectomy or dedicated stroke unit care described in published literature
- High-altitude exposure (unique to Nepal) may be an additional trigger - isolated case reports document SAH at altitude due to hypertensive surges
- Data are limited to central Nepal (Kathmandu valley); rural epidemiology is largely unknown
Sources: NINAS Nepal hospital study [PMC8827499]; Nepal stroke systematic review [PMC10519080]; Goldman-Cecil Medicine 26e; GBD 2021 Frontiers in Neurology 2025; Medscape SAH Epidemiology
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