Interindividual variation in serum cholesterol is associated with regional white matter tissue integrity in older adults.

Prior research has demonstrated links among vascular health and the occurrence of stroke, mild cognitive decline, and dementia in older adults. However, little is known about whether normal variation in vascular indicators may be related to changes in neural tissue integrity. Even less is known about how the brain is affected by cholesterol levels in the normal to moderate risk range, leading up to overt disease pathology. This study examined associations between serum lipid levels and DTI indicators of white matter (WM) structural integrity in a sample of 125 generally healthy older adults aged 43-87 years. Whole-brain voxelwise analysis, controlling for age and gender, revealed low density lipoprotein levels (LDL) as the most robust correlate of regional WM structural integrity of the measured lipids. Higher LDL was associated with decreased WM integrity in right frontal and temporal regions, the superior longitudinal fasciculus and internal/external capsules. Increasing LDL was associated with increased radial and axial diffusivity; however, more widespread statistical effects were found for radial diffusivity. These findings suggest that normal interindividual variation in lipid levels is associated with compromised regional WM integrity, even in individuals below clinical thresholds for hyperlipidemia. Given the prevalence of cholesterol-associated sequelae in older adults, and mounting evidence suggesting a vascular role in the etiology of dementia, the current data suggest that understanding the relationship between cholesterol and brain tissue microstructure may have important clinical implications for early detection of vascular-related cognitive disorders and optimal regulation of serum lipids to maintain neural health in older adults.