Risk factors for amyloid positivity in older people reporting significant memory concern.

OBJECTIVE: The goal of this study is to identify risk factors for the presence of amyloid accumulation in the brains of patients reporting subjective cognitive decline (SCD). Identifying such risk factors will help better identify patients who ought to receive neuroimaging studies to confirm plaque presence and begin intervention, as well as enhancing the study of the pathogenesis of Alzheimer's disease. METHODS: Ninety-nine SCD participants (72.2±5.6years, 57.6% female) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) underwent florbetapir PET. Logistic regression analysis was conducted to examine the relationship between the presence of an increased amyloid signal (amyloid positivity) and several potential risk factors, including: demographics, APOE ε4 genotype, family history of dementia, history of hypertension, history of cigarettes smoking, cognitive function and depressive symptoms. RESULTS: Being female was a significant risk factor for amyloid positivity (OR=4.915, 95% CI=1.709-14.139), as was being an APOE ε4 carrier (OR=2.985, 95% CI=1.084-8.219) and having a history of cigarette smoking (OR=4.091, 95% CI=1.483-11.285). CONCLUSION: Our study demonstrates that female gender, APOE ε4 genotype, and history of cigarettes smoking are associated with amyloid positivity in patients with SCD.

Plasma neurofilament light chain levels in Alzheimer's disease.

Plasma neurofilament light (NFL) levels may be a marker of neuronal injury. We examined whether plasma NFL might be a potential biomarker for the prodromal and dementia stages of AD. Participants included 193 cognitively normal (CN), 198 amnestic mild cognitive impairment (aMCI) and 187 Alzheimer's disease (AD) individuals enrolled in the Alzheimer's Disease Neuroimaging Initiative (ADNI). Plasma NFL levels were examined by the Single Molecule array (Simoa) technique. Our results showed significantly increased plasma NFL levels in both AD (50.9pg/ml) and aMCI (43.0pg/ml) groups compared to CN (34.7pg/ml) group (both p<0.001), but with substantial overlap between the groups. Plasma NFL levels in AD group was also markedly increased, compared with aMCI group (p<0.001). Plasma NFL levels were positively associated with age (r=0.355, p<0.001) and negatively with global cognition (r=-0.355, p<0.001) in all subjects. Our results suggest that plasma NFL levels may not be a useful biomarker for the diagnosis of prodromal and dementia stages of AD.