Faculty Bibliography

INTRODUCTION/BACKGROUND:Measuring plasma biomarkers effectively assesses early-stage Alzheimer's disease. METHODS:Subjects were categorized as cognitively unimpaired (CU) (n = 66), CU with subjective cognitive decline (SCD) (n = 100), and mild cognitive impairment (MCI) (n = 25). Plasma biomarkers measured were amyloid beta (Aβ) 40, Aβ42, neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), tau phosphorylated at threonine 181 (pTau181), neuroinflammatory biomarkers, and blood-brain barrier biomarkers. Amyloid and tau positron emission tomography (PET) imaging was performed in 186 and 144 subjects, respectively. RESULTS:Comparing those having MCI, both CU and SCD participants had significantly lower amyloid PET standardized uptake value ratio (SUVR) (p < 0.001; p = 0.005). Higher amyloid PET SUVR was significantly associated with higher pTau181 (p = 0.001) and a higher pTau181/Aβ42 ratio (p < 0.001). Higher tau PET SUVR was associated with lower plasma Aβ42 (p = 0.020), older age (p = 0.005), higher GFAP (p = 0.020), and lower interleukin-8 levels (p < 0.001). DISCUSSION/CONCLUSIONS:Our study supports plasma biomarker monitoring of at-risk patients at various stages of pre-dementia.

INTRODUCTION/BACKGROUND:Neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, has been linked to dementia risk, but prior studies were limited by small sample sizes. METHODS:We assessed the association between baseline NLR and incident Alzheimer's disease (AD) and Alzeimer's disease and related dementias (AD/ADRD) using electronic health records from New York University (NYU) (n = 284,530) and the Veterans Health Administration [VA] (n = 85,836) Hospitals from 2011 to 2023. AD/ADRD diagnoses were identified via International Classification of Diseases (ICD) codes ≥6 months post-baseline. Cox models and cumulative incidence functions (CIFs) adjusted for demographic and clinical variables, with death as a competing risk. RESULTS:Higher NLR was associated significantly with increased AD/ADRD risk in both cohorts (NYU hazard ratio [HR] = 1.07, 95% confidence interval [CI] 1.02-1.15; VA HR = 1.21, 95% CI 1.10-1.34). Spline analysis further confirmed a continuous dose-response relationship, and subgroup analyses showed higher risk among female and Hispanic patients. DISCUSSION/CONCLUSIONS:Elevated NLR is independently associated with higher AD/ADRD risk across diverse populations, highlighting the role of systemic inflammation and neutrophil-mediated pathways in neurodegeneration.

INTRODUCTION/BACKGROUND:We examined obstructive sleep apnea (OSA) severity's association with Alzheimer's disease (AD) plasma biomarkers, independent or synergistic with cerebrospinal fluid (CSF) amyloid, and as a proof of concept, whether plasma amyloid beta (Aβ)42/Aβ40 with OSA severity improves detection of amyloidosis and tau pathology. METHODS:In 120 cognitively normal older adults (70 with CSF data) from New York University sleep and aging studies (2013-2021), OSA severity was measured using apnea/hypopnea index with 4% desaturation; plasma Aβ40, Aβ42, tau, and neurofilament light chain (NfL) via single molecule array; CSF amyloid and tau via enzyme-linked immunosorbent assay. Associations evaluated adjusted correlations and generalized models; receiver operating characteristic analyses evaluated diagnostic accuracy. RESULTS:OSA severity correlated with plasma Aβ40 (r = 0.21), Aβ42 (r = 0.26), and Aβ42/Aβ40 (r = 0.20). Plasma tau and NfL associations depended on CSF-Aβ42. OSA severity with Aβ42/Aβ40 improved CSF amyloidosis (area under the curve [AUC] = 0.78) and tau pathology (AUC = 0.71) detection. DISCUSSION/CONCLUSIONS:OSA severity relates to elevated plasma Aβ and, with CSF amyloid, to tau/NfL. Combined plasma and OSA measures aid non-invasive AD associations' detection.

Positive airway pressure (PAP) adherence is lower in African Americans (AAs) and, possibly, Hispanics as compared to Whites. Access to other treatment modalities is also limited in these groups. In children, obstructive sleep apnea (OSA) prevalence is higher among AAs, Hispanics, and Asian Americans. AA children have lower rates of adenotonsillectomy. Interventions to dissipate misconceptions about sleep and OSA, better patient-provider communication, and standardized and targeted surveys and procedures are necessary to minimize this problem. This section will review disparities in PAP treatment and other options, as well as children's phenotypes, associated factors, and potential interventions.

Obstructive Sleep Apnea (OSA) is an extremely prevalent disorder and mostly underdiagnosed. Its prevalence is even higher among African Americans (AA), Hispanic, Asian Americans and Native Americans (NA) adults and children. AA present younger, with more severe and comorbid OSA, and are sleepier than their white counterparts. Evidence suggests this problem could be as severe in Hispanics, Asian Americans and NA. This first part of the review will focus on epidemiology and data in the adult population.

BACKGROUND:Obstructive sleep apnea (OSA) is associated with Alzheimer's disease (AD) risk. Racial-, ethnic-, and sex-specific mechanisms of OSA and AD risk were examined. METHODS:We analyzed data from 3978 polysomnography patients without cognitive decline aged ≥ 60 including 663 OSA+ patients (284 non-Hispanic White, 207 Black, 172 Hispanic) matched to OSA- cohorts (1:1, n = 663; 1:4, n = 2652) and followed for AD through 2013. RESULTS:During the 8.5 (standard deviation 1.4) year period, 358 patients developed AD. AD risk was higher for Black (adjusted hazard ratio [aHR] 2.24 [1.24-2.71]), Hispanic (aHR 1.73, [1.38-3.51]), White (aHR 1.83, [1.21-3.37]), male (aHR 2.38, [1.31-3.47]), and female (aHR 1.37, [1.14-2.41]) patients. Hypoxia, sleep fragmentation, and sleep duration (p < 0.01) were associated with increased risk. Black and Hispanic, and female patients showed stronger effects for hypoxia and duration, and fragmentation, respectively. DISCUSSION/CONCLUSIONS:Hypoxia, fragmentation, and duration may underlie racial-, ethnic-, and sex-specific effects of AD risk.

The locus coeruleus (LC) plays important roles in sleep/wake regulation and cognitive functions. LC neurons may be particularly sensitive to neural injury and serve as an early site of accumulation pathological tau in Alzheimer's disease. Obstructive sleep apnea (OSA) creates both chronic intermittent hypoxia and sleep fragmentation as potential insults to differentially sensitive neural populations including the locus coeruleus (LC). Using high field 7T imaging in cognitively normal older adults, we demonstrate that time spent with an oxygen saturation below 90% (T90), a measure of OSA's hypoxic burden, inversely correlates with LC structural integrity and explains significant variance in LC structural integrity after controlling for age, sex, and BMI. In contrast, other sleep variables such as the apnea-hypopnea index (AHI), total sleep time, and sleep efficiency did not contribute significant variance in LC structural integrity in this model. Thus, in the diagnosis of OSA, attention to hypoxic burden variables may be important in risk stratification for LC neural injury. This observation may inform future work determining whether mitigation of the hypoxemic burden from OSA can slow deterioration in LC integrity.