Lidia Glodzik

A conceptual framework for research on subjective cognitive decline in preclinical Alzheimer's disease

There is increasing evidence that subjective cognitive decline (SCD) in individuals with unimpaired performance on cognitive tests may represent the first symptomatic manifestation of Alzheimers disease (AD). The research on SCD in early AD, however, is limited by the absence of common standards. The working group of the Subjective Cognitive Decline Initiative (SCD‐I) addressed this deficiency by reaching consensus on terminology and on a conceptual framework for research on SCD in AD. In this publication, research criteria for SCD in pre‐mild cognitive impairment (MCI) are presented. In addition, a list of core features proposed for reporting in SCD studies is provided, which will enable comparability of research across different settings. Finally, a set of features is presented, which in accordance with current knowledge, increases the likelihood of the presence of preclinical AD in individuals with SCD. This list is referred to as SCD plus.

Clearance systems in the brain—implications for Alzheimer disease

Accumulation of toxic protein aggregates—amyloid-β (Aβ) plaques and hyperphosphorylated tau tangles—is the pathological hallmark of Alzheimer disease (AD). Aβ accumulation has been hypothesized to result from an imbalance between Aβ production and clearance; indeed, Aβ clearance seems to be impaired in both early and late forms of AD. To develop efficient strategies to slow down or halt AD, it is critical to understand how Aβ is cleared from the brain. Extracellular Aβ deposits can be removed from the brain by various clearance systems, most importantly, transport across the blood–brain barrier. Findings from the past few years suggest that astroglial-mediated interstitial fluid (ISF) bulk flow, known as the glymphatic system, might contribute to a larger portion of extracellular Aβ (eAβ) clearance than previously thought. The meningeal lymphatic vessels, discovered in 2015, might provide another clearance route. Because these clearance systems act together to drive eAβ from the brain, any alteration to their function could contribute to AD. An understanding of Aβ clearance might provide strategies to reduce excess Aβ deposits and delay, or even prevent, disease onset. In this Review, we describe the clearance systems of the brain as they relate to proteins implicated in AD pathology, with the main focus on Aβ.Accumulation of toxic protein aggregates-amyloid-β (Aβ) plaques and hyperphosphorylated tau tangles-is the pathological hallmark of Alzheimer disease (AD). Aβ accumulation has been hypothesized to result from an imbalance between Aβ production and clearance; indeed, Aβ clearance seems to be impaired in both early and late forms of AD. To develop efficient strategies to slow down or halt AD, it is critical to understand how Aβ is cleared from the brain. Extracellular Aβ deposits can be removed from the brain by various clearance systems, most importantly, transport across the blood-brain barrier. Findings from the past few years suggest that astroglial-mediated interstitial fluid (ISF) bulk flow, known as the glymphatic system, might contribute to a larger portion of extracellular Aβ (eAβ) clearance than previously thought. The meningeal lymphatic vessels, discovered in 2015, might provide another clearance route. Because these clearance systems act together to drive eAβ from the brain, any alteration to their function could contribute to AD. An understanding of Aβ clearance might provide strategies to reduce excess Aβ deposits and delay, or even prevent, disease onset. In this Review, we describe the clearance systems of the brain as they relate to proteins implicated in AD pathology, with the main focus on Aβ.

Declining brain glucose metabolism in normal individuals with a maternal history of Alzheimer disease

Background: At cross-section, cognitively normal individuals (NL) with a maternal history of late-onset Alzheimer disease (AD) have reduced glucose metabolism (CMRglc) on FDG-PET in the same brain regions as patients with clinical AD as compared to those with a paternal and a negative family history (FH) of AD. This longitudinal FDG-PET study examines whether CMRglc reductions in NL subjects with a maternal history of AD are progressive. Methods: Seventy-five 50- to 82-year-old NL received 2-year follow-up clinical, neuropsychological, and FDG-PET examinations. These included 37 subjects with negative family history of AD (FH−), 9 with paternal (FHp), and 20 with maternal AD (FHm). Two subjects had parents with postmortem confirmed AD. Statistical parametric mapping was used to compare CMRglc across FH groups at baseline, follow-up, and longitudinally. Results: At both time points, the FH groups were comparable for demographic and neuropsychological characteristics. At baseline and at follow-up, FHm subjects showed CMRglc reductions in the parieto-temporal, posterior cingulate, and medial temporal cortices as compared to FH− and FHp (p < 0.001). Longitudinally, FHm had significant CMRglc declines in these regions, which were significantly greater than those in FH− and FHp (p < 0.05). Conclusions: A maternal history of Alzheimer disease (AD) predisposes normal individuals to progressive CMRglc reductions in AD-vulnerable brain regions, which may be related to a higher risk for developing AD.

Pre-Clinical Detection of Alzheimer’s Disease Using FDG-PET, with or without Amyloid Imaging

The development of prevention therapies for Alzheimers disease (AD) would greatly benefit from biomarkers that are sensitive to subtle brain changes occurring in the preclinical stage of the disease. Early diagnostics is necessary to identify and treat at risk individuals before irreversible neuronal loss occurs. In vivo imaging has long been used to evaluate brain structural and functional abnormalities as predictors of future AD in non-demented persons. Prior to development of amyloid-beta (Abeta) tracers for positron emission tomography (PET), the most widely utilized PET tracer in AD was 2-[18F]fluoro-2-Deoxy-D-glucose (FDG) PET. For over 20 years, FDG-PET has been used to measure cerebral metabolic rates of glucose (CMRglc), a proxy for neuronal activity, in AD. Many studies have shown that CMRglc reductions occur early in AD, correlate with disease progression, and predict histopathological diagnosis. This paper reviews reports of clinical and preclinical CMRglc reductions observed in association with genetic and non-genetic risk factors for AD. We then briefly review brain Abeta PET imaging studies in AD and discuss the potential of combining symptoms-sensitive FDG-PET measures with pathology-specific Abeta-PET to improve the early detection of AD.

Sleep-disordered breathing advances cognitive decline in the elderly

Objective: To examine whether the presence of sleep-disordered breathing (SDB) is associated with an earlier age at mild cognitive impairment (MCI) or Alzheimer disease (AD)-dementia onset in participants from the Alzheimers Disease Neuroimaging Initiative (ADNI) cohort. We also examined whether continuous positive airway pressure (CPAP) use is associated with delayed onset of cognitive decline. Methods: From the ADNI cohort, 3 subsets with progressively stringent criteria were created in a step-wise manner. Age at MCI or AD-dementia onset was the main outcome variable. Analyses were performed separately for each subset in untreated SDB+ vs SDB− and untreated SDB+ vs CPAP+ groups. Chi-square and t tests were performed to examine between-group differences. Survival analyses were performed using the Kaplan–Meier method, compared by the log-rank test, and assessed by multivariate Cox regression adjusting for potential confounders. Results: SDB+ patients had a younger age at MCI onset in all subsets (MC1: 72.63 vs 83.67; MC2: 72.15 vs 83.45; MC3: 77.40 vs 89.89; p < 0.01). SDB+ patients had a younger age at AD-dementia onset only in our most conservative subset (AC3: 83.46 vs 88.13; p < 0.05). In a combined outcome analysis, SDB+ patients had a younger age at onset to MCI or AD-dementia in all subsets. In subsets 1 and 2, CPAP use delayed the age at MCI onset (CMC1: 72.63 vs 82.10; CMC2: 72.11 vs 82.10; p < 0.01). Conclusions: Consistent with our hypothesis, the presence of SDB was associated with an earlier age at cognitive decline. Our findings in CPAP+ participants suggest that CPAP treatment of SDB may delay progression of cognitive impairment.

Increased fibrillar amyloid-β burden in normal individuals with a family history of late-onset Alzheimer’s

Having a parent affected with late-onset Alzheimers disease (LOAD) is a major risk factor among cognitively normal (NL) individuals. This 11C-Pittsburgh Compound B (PiB)-PET study examines whether NL individuals with LOAD parents show increased fibrillar amyloid-beta (Aβ) deposition, a hallmark of Alzheimers disease (AD) pathology and whether there are parent-of-origin effects. Forty-two 50- to 80-year-old NL persons were examined with PiB-PET. These individuals included 14 NL subjects with a maternal family history (FH) of LOAD (FHm), 14 NL subjects with a paternal FH (FHp), and 14 NL subjects with a negative family history of any dementia (FH−). Statistical parametric mapping and automated regions-of-interest were used to compare cerebral-to-cerebellar PiB standardized uptake value ratios, reflecting fibrillar Aβ burden, across groups. FH groups did not differ in age, gender, education, and apolipoprotein E (ApoE) status. NL FHm subjects showed higher PiB retention in AD-affected anterior and posterior cingulate cortex (PCC), precuneus, parietal, temporal, occipital, and frontal cortices, right basal ganglia, and thalamus, compared with FH− and FHp subjects. FHp subjects showed increased PiB retention in the PCC and frontal cortex, intermediate between FHm and FH− subjects. Results remained significant after controlling for age, gender, education, and ApoE status. Children of parents with LOAD, particularly those with affected mothers, have increased fibrillar Aβ load in AD-vulnerable regions compared with controls, perhaps accounting for the known increased risk for AD. Present findings may motivate further research on familial transmission and parent-of-origin effects in LOAD.

TNF-α and antibodies to periodontal bacteria discriminate between Alzheimer’s disease patients and normal subjects

The associations of inflammation/immune responses with clinical presentations of Alzheimers disease (AD) remain unclear. We hypothesized that TNF-alpha and elevated antibodies to periodontal bacteria would be greater in AD compared to normal controls (NL) and their combination would aid clinical diagnosis of AD. Plasma TNF-alpha and antibodies against periodontal bacteria were elevated in AD patients compared with NL and independently associated with AD. The number of positive IgG to periodontal bacteria incremented the TNF-alpha classification of clinical AD and NL. This study shows that TNF-alpha and elevated numbers of antibodies against periodontal bacteria associate with AD and contribute to the AD diagnosis.

Longitudinal CSF isoprostane and MRI atrophy in the progression to AD

Very little data exist to evaluate the value of longitudinal CSF biological markers for Alzheimers disease (AD).Most studies indicate that tau and amyloid beta markers do not reflect disease progression. We now report on a longitudinal, three-time point, CSF Isoprostane (IsoP) and quantitative MRI study that examined 11 normal elderly (NL) volunteers and 6 Mild Cognitive Impairment (MCI) patients. After 4 years, all 6 MCI patients declined to AD and 2 of the NL subjects declined to MCI. At baseline and longitudinally, the MCI patients showed reduced delayed memory, increased IsoP levels, and reduced medial temporal lobe gray matter concentrations as compared to NL. A group comprised of all decliners to AD or to MCI (n = 8) was distinguished at baseline from the stable NL controls (n = 9) by IsoP with 100% accuracy.Moreover, both at baseline and longitudinally, the IsoP measures significantly improved the diagnostic and predictive outcomes of conventional memory testing and quantitative MRI measurements. These data indicate that IsoP is potentially useful for both the early detection of AD-related pathology and for monitoring the course of AD.

GREATER RISK OF ALZHEIMER’S DISEASE IN OLDER ADULTS WITH INSOMNIA

ACKNOWLEDGMENTS Conflict of Interest: This work was supported by the Fundamental Research Grant Scheme, Ministry of Higher Education, Malaysia. Dr. Noran N. Hairi’s work on this study was supported by the Public Service Department of Malaysia. The authors would like to express their appreciation to Dr. Siti Halimah Shaikh and all healthcare providers of Masjid Tanah Health Clinic, Ministry of Health, Malaysia, for their contributions to this research. Author Contributions: NNH: study concept, chief investigator, designing research protocol, data analysis, interpretation of data, and writing manuscript. AB, IM: conceptualization of research and data collection. RGC, VN, AB: critically editing of the manuscript. All authors read and approved the final manuscript. Sponsor’s Role: None.

Magnetic Resonance Imaging Improves Cerebrospinal Fluid Biomarkers in the Early Detection of Alzheimer's Disease

Little is known of combined utility of magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) biomarkers for prediction of Alzheimers disease (AD) and longitudinal data is scarce. We examined these biomarkers at baseline and longitudinally in incipient AD. Forty-five subjects [21 controls (NL-NL), 16 stable MCI (MCI-MCI), 8 MCI who declined to AD (MCI-AD)] received MRI and lumbar puncture at baseline and after 2 years. CSF measures included total and phosphorylated tau (T-tau, P-tau(231)), amyloid-beta (Abeta(42)/Abeta(40)) and isoprostane. Voxel-based morphometry identified gray matter concentration (GMC) differences best distinguishing study groups and individual GMC values were calculated. Rate of medial temporal lobe (MTL) atrophy was examined using regional boundary shift (rBS) method. At baseline, for MRI, MCI-AD showed reduced GMC-MTL, and for CSF higher CSF T-tau, P-tau(231), IP and lower Abeta(42)/Abeta(40) as compared with MCI-MCI or NL-NL. Longitudinally, rBS-MTL atrophy was higher in MCI-AD than in either MCI-MCI or NL-NL, particularly in the left hemisphere. CSF data showed longitudinally greater increases of isoprostane in MCI-AD as compared with NL-NL. Combining baseline CSF-P-tau(231) and GMC-MTL significantly increased overall prediction of AD from 74% to 84% (p(step)<0.05). These results provide support for including multiple modalities of biomarkers in the identification of memory clinic patients at increased risk for dementia.