Observational study finds Mediterranean diet linked to 25% lower hemorrhagic stroke risk — Evidence Review

A large, long-term study finds that women who closely follow a Mediterranean diet have a significantly reduced risk of both ischemic and hemorrhagic stroke. Most prior research agrees that the Mediterranean diet lowers risk of stroke and cardiovascular disease, though evidence for hemorrhagic stroke protection has been inconsistent. See the full findings published by City of Hope Comprehensive Cancer Centre.

• Many previous meta-analyses and cohort studies have shown that high adherence to the Mediterranean diet is associated with lower risk of total and ischemic stroke, but most did not find a clear protective effect for hemorrhagic stroke, making the new finding particularly notable 2 5 7.
• The current study's focus on women and its large, long-term cohort adds new detail to the evidence base, as earlier meta-analyses included both sexes and often had fewer cases of hemorrhagic stroke to analyze 1 2 5.
• While most literature supports stroke risk reduction from Mediterranean and other healthy dietary patterns, some systematic reviews report that only ischemic stroke risk is consistently reduced, suggesting that the observed benefit for hemorrhagic stroke in this study warrants further research 2 5 7.

Study Overview and Key Findings

The Mediterranean diet has long been associated with cardiovascular health, but its role in preventing different types of stroke—particularly hemorrhagic stroke—has remained less clear. With stroke continuing to be a leading cause of death and disability worldwide, understanding the impact of modifiable lifestyle factors such as diet is crucial. This new study stands out for its large sample size, exclusive focus on women, and lengthy follow-up, which help clarify the potential benefits of dietary patterns for stroke prevention.

Property	Value
Organization	City of Hope Comprehensive Cancer Centre
Journal Name	Neurology Open Access
Authors	Sophia Wang
Population	Women with no history of stroke
Sample Size	n=105,614
Methods	Observational Study
Outcome	Risk of stroke, ischemic stroke, hemorrhagic stroke
Results	Higher adherence to Mediterranean diet linked to 25% lower hemorrhagic stroke risk

The study tracked over 100,000 women in California, each free of stroke at baseline, for an average of 21 years. Participants' adherence to the Mediterranean diet was assessed using a 0-9 score based on their intake of fruits, vegetables, whole grains, legumes, olive oil, fish, moderate alcohol, and limited red meat/dairy. After adjusting for confounding factors (such as smoking, physical activity, and blood pressure), women with the highest adherence scores were 18% less likely to have any stroke, 16% less likely to have an ischemic stroke, and 25% less likely to have a hemorrhagic stroke compared to those with the lowest adherence. The findings were welcomed by independent experts, though the study's observational nature and reliance on self-reported dietary data are notable limitations.

Literature Review: Related Studies

To contextualize these findings, we searched the Consensus research database using the following queries:

1. Mediterranean diet stroke risk reduction
2. hemorrhagic stroke Mediterranean diet adherence
3. dietary patterns cerebrovascular health outcomes

The literature reveals several overarching themes regarding dietary patterns and stroke risk:

Topic	Key Findings
Does the Mediterranean diet reduce risk of total and ischemic stroke?	- High adherence to the Mediterranean diet is consistently associated with reduced risk of total and ischemic stroke across meta-analyses and cohort studies 1 2 5 6 7 9 11 13. - The protective effect appears robust across age groups and populations 1 2 5 9 13.
Is the Mediterranean diet linked to lower risk of hemorrhagic stroke?	- Most studies show no significant association between Mediterranean diet adherence and hemorrhagic stroke risk 2 5 7 8. - Some analyses suggest a possible, but not statistically significant, trend toward reduced hemorrhagic stroke risk 6.
How do healthy dietary patterns compare to Western diets for stroke prevention?	- Prudent, Mediterranean, and DASH dietary patterns are linked to lower stroke risk, while Western dietary patterns increase risk 10 11 12 13. - Low-fat diets do not show a protective effect for stroke 11.
Are the benefits of Mediterranean and healthy dietary patterns consistent across different populations?	- Protective effects of the Mediterranean diet are generally observed across sexes, ethnicities, and geographic regions, though some subgroup analyses indicate stronger effects in men or certain locations 1 2 5 6 7 9 13.

Does the Mediterranean diet reduce risk of total and ischemic stroke?

Numerous meta-analyses and cohort studies consistently report that high adherence to the Mediterranean diet is associated with lower risk of total and ischemic stroke. These findings have been observed in diverse populations and are supported by both observational and interventional studies. The new study aligns with this broader evidence, reinforcing the role of the Mediterranean diet in stroke prevention, particularly for ischemic stroke.

• Meta-analyses show relative risk reductions for total and ischemic stroke ranging from approximately 20% to 30% with high Mediterranean diet adherence 1 2 5 13.
• Benefits are seen regardless of age, sex, or geographic region, though some subgroup data suggest larger effects in men 1 2 5 9.
• Healthy dietary patterns, including the Mediterranean diet, offer protection against multiple brain and cardiovascular outcomes 1 4 9 10 13.
• The current study's observed 16% reduction in ischemic stroke risk is consistent with prior pooled estimates 1 2 5 13.

Is the Mediterranean diet linked to lower risk of hemorrhagic stroke?

Evidence for a protective effect of the Mediterranean diet against hemorrhagic stroke is weaker and less consistent than for ischemic stroke. Most large meta-analyses and cohort studies have not found statistically significant reductions in hemorrhagic stroke risk with Mediterranean diet adherence, making the new study's finding of a 25% reduction notable but somewhat divergent from previous literature.

• Recent meta-analyses and large cohort studies report no significant association between Mediterranean diet adherence and hemorrhagic stroke risk 2 5 7.
• Some studies find a non-significant trend toward reduced risk, but confidence intervals typically include the null value 6.
• Other healthy dietary patterns, such as the Nordic diet, also do not show robust protective effects for hemorrhagic stroke 8.
• The current study's finding of significant risk reduction for hemorrhagic stroke suggests a need for replication and further research, particularly as few large studies have focused on this outcome 2 5 7.

How do healthy dietary patterns compare to Western diets for stroke prevention?

Research consistently demonstrates that adherence to healthy dietary patterns—such as Mediterranean, DASH, or prudent diets—lowers stroke risk, while Western diets characterized by high intakes of red meat, processed foods, and sugar increase risk. These trends are evident for both stroke and broader cardiovascular outcomes.

• Systematic reviews and meta-analyses demonstrate that healthy dietary patterns reduce stroke and cardiovascular disease risk, while Western patterns are associated with increased or neutral risk 10 11 12 13.
• The protective effect is observed for both total stroke and ischemic stroke, but not always for hemorrhagic stroke 10 11 12.
• Low-fat diets, in contrast, are not associated with stroke risk reduction 11.
• The new study reinforces the value of a Mediterranean pattern over less healthy diets for cerebrovascular health 10 11 13.

Are the benefits of Mediterranean and healthy dietary patterns consistent across different populations?

The protective association between the Mediterranean diet and stroke risk appears broadly consistent across populations, though some studies note differences in effect size by sex or region. The new study's focus on women adds important data, as prior research has sometimes found stronger effects in men or has not analyzed results separately by sex.

• Meta-analyses show consistent risk reduction across different countries and ethnicities, although some subgroup analyses suggest slightly larger effects in men 1 2 5 6 7.
• Benefits are also observed in populations with specific risk profiles, such as individuals with diabetes 4.
• The observed protective effect in a large cohort of women in the new study complements findings from mixed-sex or male-dominated cohorts 1 2 5 9.
• Further research is needed to confirm and clarify population-specific effects 1 2 4 6.

Future Research Questions

Despite mounting evidence for the benefits of the Mediterranean diet, important questions remain regarding its mechanisms, effects on specific stroke subtypes, and applicability to broader populations. Further research, especially randomized controlled trials and studies with diverse populations and rigorous dietary assessment, will help clarify these issues.

Research Question	Relevance
Does the Mediterranean diet reduce hemorrhagic stroke risk in men and other populations?	Most studies have focused on women or have not found significant effects for hemorrhagic stroke; broader population studies are needed to determine if the protective effect is generalizable 2 5 7.
What are the biological mechanisms behind the Mediterranean diet’s impact on stroke subtypes?	Understanding the specific pathways (e.g., anti-inflammatory, blood pressure, cholesterol) by which the diet affects ischemic and hemorrhagic stroke could inform targeted prevention strategies 1 2 13.
How accurate are self-reported dietary assessments in predicting stroke risk?	Many studies, including the current one, rely on self-reported dietary data, which may introduce bias; validation with objective markers is needed 1 2 5.
Can randomized controlled trials confirm the causal relationship between Mediterranean diet adherence and stroke reduction?	Most evidence is observational; intervention studies are needed to establish causality and determine the magnitude of benefit in diverse groups 1 4 13.
Are there specific components of the Mediterranean diet that confer the greatest protection against stroke?	Identifying which foods or nutrients are most protective could refine dietary guidelines and improve stroke prevention efforts 1 2 5 11.