Associations of Pulse and Blood Pressure with Hippocampal Volume by APOE and Cognitive Phenotype: The Alzheimer's Disease Neuroimaging Initiative (ADNI)

Exploring sexual dimorphism in basal forebrain volume changes during aging and neurodegenerative diseases

Patients with neurodegenerative diseases exhibit diminished basal forebrain (BF) volume compared to healthy individuals. However, it's uncertain whether this difference is consistent between sexes. It has been reported that BF volume moderately atrophies during aging, but the effect of sex on BF volume changes during the normal aging process remains unclear. In the cross-sectional study, we observed a significant reduction in BF volume in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) compared to Healthy Controls (HCs), especially in the Ch4 subregion. Notably, significant differences in BF volume between MCI and HCs were observed solely in the female group. Additionally, we identified asymmetrical atrophy in the left and right Ch4 subregions in female patients with AD. In the longitudinal analysis, we found that aging seemed to have a minimal impact on BF volume in males. Our study highlights the importance of considering sex as a research variable in brain science.

The Association of Body Mass Index with Cognition and Alzheimer's Disease Biomarkers in the Elderly with Different Cognitive Status: A Study from the Alzheimer's Disease Neuroimaging Initiative Database

Background

The association of body mass index (BMI) with cognition and Alzheimer's disease (AD) biomarkers of the elderly remains inconclusive.

Objective

To investigate the relationship between BMI and cognition as well as AD biomarkers in the elderly with different cognitive status.

Methods

Participants with cognitively normal (CN) were included as the CN group. Participants with mild cognitive impairment and mild dementia were included as the cognitive impairment (CI) group. The relationship between BMI and AD biomarkers (cerebrospinal fluid Aβ42 and p-tau181, hippocampal volume [HV]), global cognition (Mini-Mental State Examination [MMSE]), memory, and executive function were explored.

Results

In the CI group, BMI was associated with MMSE (β= 0.03, p = 0.009), Aβ42 (β= 0.006, p = 0.029), p-tau181/Aβ42 ratio (β= -0.001, p = 0.011), and HV (β= 0.05, p < 0.001). However in the CN group, BMI exhibited associations with p-tau181 (β= 0.012, p = 0.014) and memory composite score (β= -0.04, p = 0.038), but not with p-tau181/Aβ42 ratio and HV. Moreover, mediation analysis showed that in the CI group, the positive effect of BMI on HV and MMSE score was partially mediated by diastolic blood pressure.

Conclusion

The association of BMI with cognition and AD biomarkers varies across different cognitive status. In particular, a lower BMI was associated with worse cognition, higher Aβ burden, and lower HV in individuals with CI. Clinical practice should strengthen the monitoring and management of BMI in patients with AD.

Systolic Blood Pressure Is Associated with Increased Brain Amyloid Load in Mild Cognitively Impaired Participants: Alzheimer's Disease Neuroimaging Initiatives Study

BACKGROUND

Cardiovascular disease (CVD), including elevated blood pressure (BP), is known to promote Alzheimer's disease (AD) risk. Although brain amyloid load is a recognized hallmark of pre-symptomatic AD, its relationship to increased BP is less known. The objective of this study was to examine the relationship of BP to brain estimates of amyloid-β (Aβ) and standard uptake ratio (SUVr). We hypothesized that increased BP is associated with increased SUVr.

METHODS

Using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), we stratified BP according to the Seventh Joint National Committee (JNC) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure Classification (JNC VII). Florbetapir (AV-45) SUVr was derived from the averaged frontal, anterior cingulate, precuneus, and parietal cortex relative to the cerebellum. A linear mixed-effects model enabled the elucidation of amyloid SUVr relationships to BP. The model discounted the effects of demographics, biologics, and diagnosis at baseline within APOE genotype groups. The least squares means procedure was used to estimate the fixed-effect means. All analyses were performed using the Statistical Analysis System (SAS).

RESULTS

In non-ɛ4 carrier MCI subjects, escalating JNC categories of BP was associated with increasing mean SUVr using JNC-4 as a reference point (low-normal (JNC1) p = 0.018; normal (JNC-1) p = 0.039; JNC-2 p = 0.018 and JNC-3 p = 0.04). A significantly higher brain SUVr was associated with increasing BP despite adjustment for demographics and biological variables in non-ɛ4 carriers but not in ɛ4-carriers. This observation supports the view that CVD risk may promote increased brain amyloid load, and potentially, amyloid-mediated cognitive decline.

CONCLUSION

Increasing levels of JNC classification of BP is dynamically associated with significant changes in brain amyloid burden in non-ɛ4 carriers but not in ɛ4-carrier MCI subjects. Though not statistically significant, amyloid burden tended to decrease with increasing BP in ɛ4 homozygote, perhaps motivated by increased vascular resistance and the need for higher brain perfusion pressure.

Unsupervised Machine Learning to Identify Separable Clinical Alzheimer's Disease Sub-Populations

Heterogeneity among Alzheimer's disease (AD) patients confounds clinical trial patient selection and therapeutic efficacy evaluation. This work defines separable AD clinical sub-populations using unsupervised machine learning. Clustering (t-SNE followed by k-means) of patient features and association rule mining (ARM) was performed on the ADNIMERGE dataset from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Patient sociodemographics, brain imaging, biomarkers, cognitive tests, and medication usage were included for analysis. Four AD clinical sub-populations were identified using between-cluster mean fold changes [cognitive performance, brain volume]: cluster-1 represented least severe disease [+17.3, +13.3]; cluster-0 [-4.6, +3.8] and cluster-3 [+10.8, -4.9] represented mid-severity sub-populations; cluster-2 represented most severe disease [-18.4, -8.4]. ARM assessed frequently occurring pharmacologic substances within the 4 sub-populations. No drug class was associated with the least severe AD (cluster-1), likely due to lesser antecedent disease. Anti-hyperlipidemia drugs associated with cluster-0 (mid-severity, higher volume). Interestingly, antioxidants vitamin C and E associated with cluster-3 (mid-severity, higher cognition). Anti-depressants like Zoloft associated with most severe disease (cluster-2). Vitamin D is protective for AD, but ARM identified significant underutilization across all AD sub-populations. Identification and feature characterization of four distinct AD sub-population "clusters" using standard clinical features enhances future clinical trial selection criteria and cross-study comparative analysis.

High pulse pressure is a risk factor for prodromal Alzheimer's disease: a longitudinal study

It has been increasingly evident that pulse pressure (PP) is associated with Alzheimer's disease (AD) but whether PP increases AD risk and the mechanism responsible for this association remains unclear. To investigate the effects of PP in the process of AD, we have evaluated the cross-sectional and longitudinal associations of PP with AD biomarkers, brain structure and cognition and have assessed the effect of PP on AD risk in a large sample (n= 1,375) from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Multiple linear regression and mixed-model regression were employed in cross-sectional and longitudinal analyses respectively. Clinical disease progression was assessed using Cox proportional hazards models. High PP was associated with lower β-amyloid 42 (Aβ₄₂) (P= .015), and higher total tau (T-tau) (P= .011), phosphorylated tau (P-tau) (P= .003), T-tau/Aβ₄₂ (P= .004) and P-tau/Aβ₄₂ (P = .001), as well as heavier cortical amyloid-beta burden (P= .011). Longitudinally, baseline high PP was significantly associated with hippocampal atrophy (P= .039), entorhinal atrophy (P= .031) and worse memory performance (P= .058). Baseline high PP showed more rapid progression than those with normal PP (P <.001). These results suggest PP elevation could increase AD risk, which may be driven by amyloid plaques and subclinical neurodegeneration.

Low Hippocampal Dentate Gyrus Volume Associated With Hypertension-Related Cognitive Impairment

Hypertension increases the risk of cognitive impairment independent of detectable stroke or cerebral lesions. However, the principal pathophysiological basis of this increase has not been fully elucidated. The present study investigates the relationships among blood pressure, hippocampal subfields volume, and cognitive function in a relatively young non-stroke population. A total of 59 non-stroke non-dementia subjects (mean age, 57.2 ± 4.9 years) were enrolled. All subjects were subjected to complete assessment of vascular risk factors including 24-hour blood pressure monitoring, various neuropsychological tests, and 3D-T1 MR scan. Freesurfer V6.0 was used for segmentation of hippocampal subfields. Our analyses revealed that both 24-hour and daytime mean systolic blood pressure (SBP) were significantly associated with the low volume of the left DG. Higher coefficient of variation (CV) of daytime SBP was significantly associated with lower volume of the left Cornu Ammonis 4 and dentate gyrus (DG) region. Both higher CV of 24-hour mean SBP and daytime SBP were significantly associated with lower performance in both executive and linguistic function. The low volume of the left DG was significantly associated with the low performance in linguistic function. Our findings support that reduced DG volume and increased SBP variability associated with hypertension-related cognitive impairment.