Risk Factors for Amyloid, Neurodegeneration Differ in Alzheimer Disease

Amyloid deposition and neurodegeneration are typically seen as 2 intertwined parts of the pathology of Alzheimer disease, but a study suggests that risk factors affecting these components of Alzheimer disease may differ.

To investigate, researchers from the Mayo Clinic prospectively analyzed 942 patients aged 70 to 90 years who were enrolled in the Mayo Clinic Study of Aging in Olmsted County, Minnesota. The average age of participants was 80 years, and 45% of participants were women. Participants underwent magnetic resonance imaging and Pittsburgh compound B-positron emission tomography (PET) scans.

The risk factors evaluated were demographics, APOE status, intellectual enrichment, midlife risk factors (physical inactivity, obesity, smoking, diabetes, hypertension, and dyslipidemia), and the total number of late-life cardiac and metabolic conditions.
___________________________________________________________________________________________________________________________________________________________________
RELATED CONTENT
Cognitive Impairment Concerns: ‘Worried Well’ or Early Alzheimer Disease? 
New Study Detects Relationship Between Head Trauma and Alzheimer’s Disease
___________________________________________________________________________________________________________________________________________________________________

Other than known risk factors such as demographics (age and gender) and APOE genotype, only midlife dyslipidemia was linked with amyloid deposition. However, neurodegeneration was associated with obesity, smoking, diabetes, hypertension, and cardiac and metabolic conditions.

Notably, intellectual enrichment was not a factor linked with either amyloid deposition or neurodegeneration. The researchers said that this might mean that intellectual enrichment may protect against cognitive decline while having a minimal impact on Alzheimer disease biomarkers.

Participants aged 85 or more years who did not have Alzheimer pathology were classified as exceptional agers, and study results showed small-to-moderate effect sizes (Cohen’s d > 0.2) for several factors, except job score and midlife hypertension, in predicting that these individuals would age without Alzheimer disease pathology.

The study used neurodegeneration as a surrogate for tau pathology, but researchers recommend that future studies should conduct tau PET imaging instead.

—Lauren LeBano

Reference

Vemuri P, Knopman DS, Lesnick TG. Evaluation of amyloid protective factors and Alzheimer disease neurodegeneration protective factors in elderly individuals. JAMA Neurol. Published online April 17, 2017. doi: 10.1001/jamaneurol.2017.0244.