Elevated BMI as a Causal Risk Factor for Vascular Dementia: Mendelian Randomization Insights
Overview
This study provides evidence that higher body mass index (BMI) causally increases the risk of vascular-related dementia. Mendelian randomization analyses demonstrated that the effect of elevated BMI on vascular dementia risk is partly mediated by increased blood pressure.
Background
Obesity is a known risk factor for multiple diseases including cardiovascular conditions and certain cancers, but its causal role in dementia, particularly vascular dementia, has been unclear. Observational studies have shown associations between midlife obesity and increased dementia risk, but confounding factors limit causal inference. Mendelian randomization (MR) offers a genetic approach to assess causality by using genetic variants as proxies for BMI, minimizing confounding and reverse causation. Understanding whether BMI causally contributes to vascular dementia and the mediating role of metabolic risk factors could inform prevention strategies.
Data Highlights
Analysis Type
Odds Ratio (OR) per 1-SD Higher BMI
95% Confidence Interval
Meta-analysis of 2 one-sample MR studies
1.63
1.13 - 2.35
Two-sample MR (Inverse-variance weighted)
1.54
1.10 - 2.16
Two-sample MR (Weighted median)
1.87
1.22 - 2.85
Two-sample MR (Weighted mode)
1.98
1.21 - 3.22
Systolic blood pressure mediation
18%
10% - 61%
Diastolic blood pressure mediation
25%
13% - 75%
Key Findings
Higher genetically predicted BMI is associated with increased risk of vascular-related dementia, with ORs ranging from 1.54 to 1.98 per 1 standard deviation increase in BMI.
Meta-analysis of individual-level data from two cohorts confirmed the association with an OR of 1.63.
Blood pressure, both systolic and diastolic, mediates a significant portion (18%-25%) of the effect of BMI on vascular dementia risk.
No consistent mediation effect was found for hyperlipidemia, hyperglycemia, or low-grade inflammation.
The association between BMI and vascular dementia is linear genetically, contrasting with the observational U-shaped relationship.
These findings support BMI and blood pressure as modifiable risk factors for vascular dementia prevention.
Clinical Implications
Clinicians should recognize elevated BMI as a causal risk factor for vascular dementia, emphasizing the importance of weight management in midlife to reduce dementia risk. Blood pressure control may partially mitigate this risk, highlighting the need for integrated cardiovascular and metabolic risk factor management in dementia prevention strategies.
Conclusion
This Mendelian randomization study supports a causal role of elevated BMI in increasing vascular dementia risk, partly mediated by hypertension. Targeting obesity and blood pressure could be effective approaches to reduce the burden of vascular dementia.
References
Nordestgaard et al. 2024 -- Elevated Body Mass Index as a Potential Causal Contributor to Vascular Dementia
