This paper is one year old, but I repost it because we have the 201 results. The 434 treated had less brain atrophy, but this was not statistically significant. The highlights of this paper support a causal relationship between brain iron and gray matter volumes = brain atrophy. The other highlights are also interesting. It looks clear that with bigger patient numbers in the 201 study could have confirmed 434 to reduce brain atrophy significantly.

Highlights

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  Genetic evidence supports a causal relationship between higher brain iron with lower grey matter volumes in specific areas.
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  Higher genetically predicted thalamus R2* increased risk of non-Alzheimer's dementia only.
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  Higher genetically predicted iron in the caudate, putamen, and substantia nigra increased risk of Parkinson's disease.
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  Higher iron deposition in specific subcortical brain regions caused non-Alzheimer's dementia and Parkinson's disease.

Here is the paper

Observational Study

Neurobiol Dis

. 2024 Jul:197:106539.

doi: 10.1016/j.nbd.2024.106539. Epub 2024 May 22.

MRI-derived brain iron, grey matter volume, and risk of dementia and Parkinson's disease: Observational and genetic analysis in the UK Biobank cohort

Francesco Casanova ¹, Qu Tian ², Daniel S Williamson ³, Yong Qian ², David Zweibaum ², Jun Ding ², Janice L Atkins ¹, David Melzer ¹, Luigi Ferrucci ⁴, Luke C Pilling ⁵

Affiliations Expand

• PMID: 38789058

PMCID: PMC12048010 DOI: 10.1016/j.nbd.2024.106539

Abstract

Background: Iron overload is observed in neurodegenerative diseases, especially Alzheimer's disease (AD) and Parkinson's disease (PD). Homozygotes for the iron-overload (haemochromatosis) causing HFE p.C282Y variant have increased risk of dementia and PD. Whether brain iron deposition is causal or secondary to the neurodegenerative processes in the general population is unclear.

Methods: We analysed 39,533 UK Biobank participants of European genetic ancestry with brain MRI data. We studied brain iron estimated by R2* and quantitative susceptibility mapping (QSM) in 8 subcortical regions: accumbens, amygdala, caudate, hippocampus, pallidum, putamen, substantia nigra, and thalamus. We performed genome-wide associations studies (GWAS) and used Mendelian Randomization (MR) methods to estimate the causal effect of brain iron on grey matter volume, and risk of AD, non-AD and PD. We also used MR to test whether genetic liability to AD or PD causally increased brain iron (R2* and QSM).

Findings: In GWAS of R2* and QSM we replicated 83% of previously reported genetic loci and identified 174 further loci across all eight brain regions. Higher genetically predicted brain iron, using both R2* and QSM, was associated with lower grey matter volumes in the caudate, putamen and thalamus (e.g., Beta-putamenQSM: -0.37, p = 2*10-46). Higher genetically predicted thalamus R2* was associated with increased risk of non-AD dementia (OR 1.36(1.16;1.60), p = 2*10-4) but not AD (p > 0.05). In males, genetically predicted putamen R2* increased non-AD dementia risk, but not in females. Higher genetically predicted iron in the caudate, putamen, and substantia nigra was associated with an increased risk of PD (Odds Ratio QSM ∼ substantia-nigra 1.21(1.07;1.37), p = 0.003). Genetic liability to AD or PD was not associated with R2* or QSM in the dementia or PD-associated regions.

Interpretation: Our genetic analysis supports a causal effect of higher iron deposition in specific subcortical brain regions for Parkinson's disease, grey matter volume, and non-Alzheimer's dementia.