Small vessel cerebrovascular disease, visualized as white matter hyperintensities on T2-weighted MRI, contributes to the clinical presentation of Alzheimer’s disease. However, the extent to which cerebrovascular disease represents an independent pathognomonic feature of Alzheimer's disease or directly promotes Alzheimer’s pathology is unclear. The purpose of this study was to examine the association between white matter hyperintensities and plasma levels of tau and to determine if white matter hyperintensities and tau levels interact to predict Alzheimer’s disease diagnosis. To confirm that cerebrovascular disease promotes tau pathology, we examined tau fluid biomarker concentrations and pathology in a mouse model of ischemic injury. Three hundred ninety-one participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI; 74.5 ± 7.1 years of age) were included in this cross-sectional analysis. Participants had measurements of plasma total-tau, CSF beta amyloid, and white matter hyperintensities, and were diagnosed clinically as Alzheimer’s disease (n = 97), mild cognitive impairment (n = 186), or cognitively normal control (n = 108). We tested the relationship between plasma tau concentration and white matter hyperintensity volume across diagnostic groups. We also examined the extent to which white matter hyperintensity volume, plasma tau, amyloid positivity status, and the interaction between white matter hyperintensities and plasma tau correctly classifies diagnostic category. Increased white matter hyperintensity volume was associated with higher plasma tau concentration, particularly among those diagnosed clinically with Alzheimer’s disease. Presence of brain amyloid and the interaction between plasma tau and white matter hyperintensity volume distinguished Alzheimer’s disease and mild cognitive impairment participants from controls with 77.6% and 63.3% accuracy, respectively. In 63 ADNI participants who came to autopsy (82.33 ± 7.18 age at death) we found that higher degrees of arteriosclerosis were associated with higher Braak staging, indicating a positive relationship between cerebrovascular disease and neurofibrillary pathology. In a transient middle cerebral artery occlusion (tMCAo) mouse model, aged mice that received tMCAo, but not sham surgery, had increased plasma and CSF tau concentrations, induced myelin loss, and hyperphosphorylated tau pathology in the ipsilateral hippocampus and cerebral hemisphere. These findings demonstrate a relationship between cerebrovascular disease, operationalized as white matter hyperintensities, and tau levels, indexed in the plasma, suggesting that hypoperfusive injury promotes tau pathology. This potential causal association is supported by the demonstration that transient cerebral artery occlusion induces white matter damage, increases biofluidic markers of tau, and promotes cerebral tau hyperphosphorylation in older adult mice.

Objective: Adults with Down syndrome (DS) develop Alzheimer disease (AD) pathology by their 5th decade. Compared with the general population, traditional vascular risks in adults with DS are rare, allowing examination of cerebrovascular disease in this population and insight into its role in AD without the confound of vascular risk factors. We examined in vivo magnetic resonance imaging (MRI)-based biomarkers of cerebrovascular pathology in adults with DS, and determined their cross-sectional relationship with age, beta-amyloid pathology, and mild cognitive impairment or clinical AD diagnostic status. Methods: Participants from the Biomarkers of Alzheimer's Disease in Down Syndrome study (n = 138, 50 ± 7 years, 39% women) with MRI data and a subset (n = 90) with amyloid positron emission tomography (PET) were included. We derived MRI-based biomarkers of cerebrovascular pathology, including white matter hyperintensities (WMH), infarcts, cerebral microbleeds, and enlarged perivascular spaces (PVS), as well as PET-based biomarkers of amyloid burden. Participants were characterized as cognitively stable (CS), mild cognitive impairment-DS (MCI-DS), possible AD dementia, or definite AD dementia based on in-depth assessments of cognition, function, and health status. Results: There were detectable WMH, enlarged PVS, infarcts, and microbleeds as early as the 5th decade of life. There was a monotonic increase in WMH volume, enlarged PVS, and presence of infarcts across diagnostic groups (CS < MCI-DS < possible AD dementia < definite AD dementia). Higher amyloid burden was associated with a higher likelihood of an infarct. Interpretation: The findings highlight the prevalence of cerebrovascular disease in adults with DS and add to a growing body of evidence that implicates cerebrovascular disease as a core feature of AD and not simply a comorbidity.

Introduction Positron emission tomography (PET) imaging for neurofibrillary tau allows investigation of the in vivo spatiotemporal progression of Alzheimer's disease (AD) pathology. We evaluated the suitability of 18F‐MK‐6240 in a clinical sample and determined the relationships among 18F‐MK‐6240 binding, age, cognition, and cerebrospinal fluid (CSF)‐based AD biomarkers. Methods Participants (n = 101, 72 ± 9 years, 52% women) underwent amyloid PET, tau PET, structural T1‐weighted magnetic resonance imaging, and neuropsychological evaluation. Twenty‐one participants had lumbar puncture for CSF measurement of amyloid beta (Aβ)42, tau, and phosphorylated tau (p‐tau). Results 18F‐MK‐6240 recapitulated Braak staging and correlated with CSF tau and p‐tau, normalized to Aβ42. 18F‐MK‐6240 negatively correlated with age across Braak regions in amyloid‐positive participants, consistent with greater tau pathology in earlier onset AD. Domain‐specific, regional patterns of 18F‐MK‐6240 binding were associated with reduced memory, executive, and language performance, but only in amyloid‐positive participants. Discussion 18F‐MK‐6240 can approximate Braak staging across the AD continuum and provide region‐dependent insights into biomarker‐based AD models.

ObjectiveTo test the hypotheses that hypertension and nocturnal blood pressure are related to white matter hyperintensity (WMH) volume, an MRI marker of small vessel cerebrovascular disease, and that WMH burden statistically mediates the association of hypertension and dipping status with memory functioning, we examined the relationship of hypertension and dipping status on WMH volume and neuropsychological test scores in middle-aged and older adults.MethodsParticipants from the community-based Maracaibo Aging Study received ambulatory 24-hour blood pressure monitoring, structural MRI, and neuropsychological assessment. Four hundred thirty-five participants (mean ± SD age 59 ± 13 years, 71% women) with available ambulatory blood pressure, MRI, and neuropsychological data were included in the analyses. Ambulatory blood pressure was used to define hypertension and dipping status (i.e., dipper, nondipper, and reverse dipper based on night/day blood pressure ratio <0.9, 0.9–1, and >1, respectively). Outcome measures included regional WMH and memory functioning derived from a neuropsychological test battery.ResultsThe majority of the participants (59%) were hypertensive. Ten percent were reverse dippers, and 40% were nondippers. Reverse dipping in the presence of hypertension was associated with particularly elevated periventricular WMH volume (F2,423 = 3.78, p = 0.024) and with lowered memory scores (F2,423 = 3.911, p = 0.021). Periventricular WMH volume mediated the effect of dipping status and hypertension on memory (β = −4.1, 95% confidence interval −8.7 to −0.2, p < 0.05).ConclusionReverse dipping in the presence of hypertension is associated with small vessel cerebrovascular disease, which, in turn, mediates memory functioning. These results point toward reverse dipping as a marker of poor nocturnal blood pressure control, particularly among hypertensive individuals, with potentially pernicious effects on cerebrovascular health and associated cognitive function.