Age-related differences in macromolecular resonances observed in ultra-short-TE STEAM MR spectra at 7T.

PURPOSE: To understand how macromolecular content varies in the human brain with age in a large cohort of healthy subjects. METHODS: In-vivo 1H-MR spectra were acquired using ultra-short TE STEAM at 7T in the posterior cingulate cortex. Macromolecular content was studied in 147 datasets from a cohort ranging in age from 19 to 89 y. Three fitting approaches were used to evaluate the macromolecular content: (1) a macromolecular resonances model developed for this study; (2) LCModel-simulated macromolecules; and (3) a combination of measured and LCModel-simulated macromolecules. The effect of age on the macromolecular content was investigated by considering age both as a continuous variable (i.e., linear regressions) and as a categorical variable (i.e., multiple comparisons among sub-groups obtained by stratifying data according to age by decade). RESULTS: While weak age-related effects were observed for macromolecular peaks at ˜0.9 (MM09), ˜1.2 (MM12), and ˜1.4 (MM14) ppm, moderate to strong effects were observed for peaks at ˜1.7 (MM17), and ˜2.0 (MM20) ppm. Significantly higher MM17 and MM20 content started from 30 to 40 y of age, while for MM09, MM12, and MM14, significantly higher content started from 60 to 70 y of age. CONCLUSIONS: Our findings provide insights into age-related differences in macromolecular contents and strengthen the necessity of using age-matched measured macromolecules during quantification.

Scyllo-inositol: Transverse relaxation time constant at 3 T and concentration changes associated with aging and alcohol use.

The goals of this study were to measure the apparent transverse relaxation time constant, T2 , of scyllo-inositol (sIns) in young and older healthy adults' brains and to investigate the effect of alcohol usage on sIns in young and older healthy adults' brains, using proton magnetic resonance spectroscopy (MRS) at 3 T. Twenty-nine young adults (age 21 ± 1 years) and 24 older adults (age 74 ± 3 years) participated in this study. MRS data were acquired from two brain regions (the occipital cortex and posterior cingulate cortex) at 3 T. The T2 of sIns was measured using a localization by adiabatic selective refocusing (LASER) sequence at various echo times, while the sIns concentrations were measured using a short-echo-time stimulated echo acquisition mode (STEAM) sequence. A trend towards lower T2 relaxation values of sIns in older adults was observed, although these were not significant. sIns concentration was higher with age in both brain regions and was significantly higher in the young when considering alcohol consumption of more than two drinks per week. This study shows that differences in sIns can be found in two distinct regions of the brain across two age groups, potentially reflecting normal aging. In addition, it is important to take into account alcohol consumption when reporting the sIns level in the brain.

Changes in the intracellular microenvironment in the aging human brain.

Normal brain aging is associated with changes occurring at all levels. This study investigates age-related differences in the brain intracellular microenvironment by comparing the apparent diffusion coefficients (ADC) and apparent transverse relaxation time constants (T2) of 5 neurochemicals (i.e., total N-acetyl-aspartate, total creatine, total choline, glutamate, and myo-inositol) between young and older adults. Thirty-two young healthy adults (18-22 years) and 26 older healthy adults (70-83 years) were recruited. Three brain regions were studied at 3 T: prefrontal, posterior cingulate and occipital cortices. ADC and T2 were measured using stimulated echo acquisition mode and localization by adiabatic selective refocusing sequences, respectively. This study shows that the diffusivities of several neurochemicals are higher in older than in younger adults. In contrast, shorter apparent T2 values for several metabolites were measured in older adults. Age-related difference in ADC and apparent T2 of metabolites seem to be region-specific. Furthermore, this study shows that it is feasible to observe age-related differences in the cellular microenvironment of neurochemicals in the normal aging brain.

Benefits and Harms of Prescription Drugs and Supplements for Treatment of Clinical Alzheimer-Type Dementia.

BACKGROUND: Effects of drug treatment of clinical Alzheimer-type dementia (CATD) are uncertain. PURPOSE: To summarize evidence on the effects of prescription drugs and supplements for CATD treatment. DATA SOURCES: Electronic bibliographic databases (inception to November 2019), ClinicalTrials.gov (to November 2019), and systematic review bibliographies. STUDY SELECTION: English-language trials of prescription drug and supplement treatment in older adults with CATD that report cognition, function, global measures, behavioral and psychological symptoms of dementia (BPSD), or harms. Minimum treatment was 24 weeks (≥2 weeks for selected BPSD). DATA EXTRACTION: Studies with low or medium risk of bias (ROB) were analyzed. Two reviewers rated ROB. One reviewer extracted data; another verified extraction accuracy. DATA SYNTHESIS: Fifty-five studies reporting non-BPSD outcomes (most ≤26 weeks) and 12 reporting BPSD (most ≤12 weeks) were analyzed. Across CATD severity, mostly low-strength evidence suggested that, compared with placebo, cholinesterase inhibitors produced small average improvements in cognition (median standardized mean difference [SMD], 0.30 [range, 0.24 to 0.52]), no difference to small improvement in function (median SMD, 0.19 [range, -0.10 to 0.22]), no difference in the likelihood of at least moderate improvement in global clinical impression (median absolute risk difference, 4% [range, 2% to 4%]), and increased withdrawals due to adverse events. In adults with moderate to severe CATD receiving cholinesterase inhibitors, low- to insufficient-strength evidence suggested that, compared with placebo, add-on memantine inconsistently improved cognition and improved global clinical impression but not function. Evidence was mostly insufficient about prescription drugs for BPSD and about supplements for all outcomes. LIMITATION: Most drugs had few trials without high ROB, especially for supplements, active drug comparisons, BPSD, and longer trials. CONCLUSION: Cholinesterase inhibitors and memantine slightly reduced short-term cognitive decline, and cholinesterase inhibitors slightly reduced reported functional decline, but differences versus placebo were of uncertain clinical importance. Evidence was mostly insufficient on drug treatment of BPSD and on supplements for all outcomes. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality. (PROSPERO: CRD42018117897).

Accuracy of Biomarker Testing for Neuropathologically Defined Alzheimer Disease in Older Adults With Dementia.

BACKGROUND: Biomarker accuracy for Alzheimer disease (AD) is uncertain. PURPOSE: To summarize evidence on biomarker accuracy for classifying AD in older adults with dementia. DATA SOURCES: Electronic bibliographic databases (searched from January 2012 to November 2019 for brain imaging and cerebrospinal fluid [CSF] tests and from inception to November 2019 for blood tests), ClinicalTrials.gov (to November 2019), and systematic review bibliographies. STUDY SELECTION: English-language studies evaluating the accuracy of brain imaging, CSF testing, or blood tests for distinguishing neuropathologically defined AD from non-AD among older adults with dementia. Studies with low or medium risk of bias were analyzed. DATA EXTRACTION: Two reviewers rated risk of bias. One extracted data; the other verified accuracy. DATA SYNTHESIS: Fifteen brain imaging studies and 9 CSF studies met analysis criteria. Median sensitivity and specificity, respectively, were 0.91 and 0.92 for amyloid positron emission tomography (PET), 0.89 and 0.74 for 18F-labeled fluorodeoxyglucose (18F-FDG) PET, 0.64 and 0.83 for single-photon emission computed tomography, and 0.91 and 0.89 for medial temporal lobe atrophy on magnetic resonance imaging (MRI). Individual CSF biomarkers and ratios had moderate sensitivity (range, 0.62 to 0.83) and specificity (range, 0.53 to 0.69); in the few direct comparisons, ß-amyloid 42 (Aß42)/phosphorylated tau (p-tau) ratio, total tau (t-tau)/Aß42 ratio, and p-tau appeared more accurate than Aß42 and t-tau alone. Single studies suggested that amyloid PET, 18F-FDG PET, and CSF test combinations may add accuracy to clinical evaluation. LIMITATIONS: Studies were small, biomarker cut points and neuropathologic AD were inconsistently defined, and methods with uncertain applicability to typical clinical settings were used. Few studies directly compared biomarkers, assessed test combinations, evaluated whether biomarkers improved classification accuracy when added to clinical evaluation, or reported harms. CONCLUSION: In methodologically heterogeneous studies of uncertain applicability to typical clinical settings, amyloid PET, 18F-FDG PET, and MRI were highly sensitive for neuropathologic AD. Amyloid PET, 18F-FDG PET, and CSF test combinations may add accuracy to clinical evaluation. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality. (PROSPERO: CRD42018117897).

Brief Cognitive Tests for Distinguishing Clinical Alzheimer-Type Dementia From Mild Cognitive Impairment or Normal Cognition in Older Adults With Suspected Cognitive Impairment.

BACKGROUND: The accuracy and harms of brief cognitive tests for identifying clinical Alzheimer-type dementia (CATD) are uncertain. PURPOSE: To summarize evidence on accuracy and harms of brief cognitive tests for CATD in older adults with suspected cognitive impairment. DATA SOURCES: Electronic bibliographic databases (from inception to November 2019) and systematic review bibliographies. STUDY SELECTION: English-language, controlled observational studies in older adults that evaluated the accuracy of brief cognitive tests (standalone tests; memory, executive function, and language tests; and brief multidomain batteries) for distinguishing CATD from mild cognitive impairment (MCI) or normal cognition as defined by established diagnostic criteria. Studies with low or medium risk of bias (ROB) were analyzed. DATA EXTRACTION: Two reviewers rated ROB. One reviewer extracted data; the other verified extraction accuracy. DATA SYNTHESIS: Fifty-seven studies met analysis criteria. Many brief, single cognitive tests were highly sensitive and specific for distinguishing CATD from normal cognition. These included standalone tests (clock-drawing test, median sensitivity 0.79 and specificity 0.88 [8 studies]; Mini-Mental State Examination, 0.88 and 0.94 [7 studies]; Montreal Cognitive Assessment, 0.94 and 0.94 [2 studies]; and Brief Alzheimer Screen, 0.92 and 0.97 [1 study]), memory tests (list delayed recall, 0.89 and 0.94 [5 studies]), and language tests (category fluency, 0.92 and 0.89 [9 studies]). Accuracy was lower in distinguishing mild CATD from normal cognition and distinguishing CATD from MCI. No studies reported on testing harms. LIMITATIONS: Studies were small. Few test metrics were evaluated by multiple studies. Few studies directly compared different tests, scores, cut points, or test combinations. CONCLUSION: Many brief, single cognitive tests accurately distinguish CATD from normal cognition in older adults but are less accurate in distinguishing mild CATD from normal cognition or CATD from MCI. No studies reported on testing harms. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality. (PROSPERO: CRD42018117897).

Efficacy and Safety of Testosterone Treatment in Men: An Evidence Report for a Clinical Practice Guideline by the American College of Physicians.

Background: Testosterone treatment rates in adult men have increased in the United States over the past 2 decades. Purpose: To assess the benefits and harms of testosterone treatment for men without underlying organic causes of hypogonadism. Data Sources: English-language searches of multiple electronic databases (January 1980 to May 2019) and reference lists from systematic reviews. Study Selection: 38 randomized controlled trials (RCTs) of at least 6 months' duration that evaluated transdermal or intramuscular testosterone therapies versus placebo or no treatment and reported prespecified patient-centered outcomes, as well as 20 long-term observational studies, U.S. Food and Drug Administration review data, and product labels that reported harms information. Data Extraction: Data extraction by a single investigator was confirmed by a second, 2 investigators assessed risk of bias, and evidence certainty was determined by consensus. Data Synthesis: Studies enrolled mostly older men who varied in age, symptoms, and testosterone eligibility criteria. Testosterone therapy improved sexual functioning and quality of life in men with low testosterone levels, although effect sizes were small (low- to moderate-certainty evidence). Testosterone therapy had little to no effect on physical functioning, depressive symptoms, energy and vitality, or cognition. Harms evidence reported in trials was judged to be insufficient or of low certainty for most harm outcomes. No trials were powered to assess cardiovascular events or prostate cancer, and trials often excluded men at increased risk for these conditions. Observational studies were limited by confounding by indication and contraindication. Limitation: Few trials exceeded a 1-year duration, minimum important outcome differences were often not established or reported, RCTs were not powered to assess important harms, few data were available in men aged 18 to 50 years, definitions of low testosterone varied, and study entry criteria varied. Conclusion: In older men with low testosterone levels without well-established medical conditions known to cause hypogonadism, testosterone therapy may provide small improvements in sexual functioning and quality of life but little to no benefit for other common symptoms of aging. Long-term efficacy and safety are unknown. Primary Funding Source: American College of Physicians. (PROSPERO: CRD42018096585).

Periprocedural Changes in Cognitive Function After Transcatheter and Surgical Aortic Valve Replacement: Results From a Pilot Study Assessing Cognition in Elderly Veterans.

BACKGROUND: There is paucity of data comparing periprocedural changes in cognitive function between surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR). METHODS: We enrolled patients with severe aortic stenosis scheduled to undergo TAVR or SAVR at the discretion of the heart team. Participants completed a cognitive battery before and 3 months after TAVR or SAVR, including the Montreal Cognitive Assessment (MoCA), phonemic (letter) verbal fluency, semantic (category) verbal fluency, and the Trail Making test (TMT) A and B. Periprocedural differences in cognition were compared within (pre/post procedure) and between groups using the paired-samples or independent-sample t-test, respectively. The Wilcoxon test was used for non-normally distributed data. RESULTS: Of the 63 patients (95% men) included, a total of 43 underwent TAVR and 20 underwent SAVR. Patients undergoing TAVR were older than SAVR patients (78 ± 8 years vs 70 ± 7 years, respectively; P<.001), but had similar STS surgical risk scores (4.9% vs 4.7%, respectively; P=.79). At baseline, there were no differences in cognition. At 3 months post TAVR or SAVR, there were no significant differences for MoCA blind score (16 ± 3 vs 16 ± 3, respectively; P=.61), correct responses in semantic fluency (15 ± 5 vs 15 ± 6, respectively; P=.93), correct responses in phonemic fluency (30 ± 12 vs 28 ± 15, respectively; P=.87), TMT A completion time (54 sec [IQR, 42-65 sec] vs 31 sec [IQR, 28-69 sec], respectively; P=.07), or TMT B completion time (161 sec [IQR, 118-300 sec] vs 173 sec [IQR, 110-300 sec], respectively; P=.87). CONCLUSIONS: In this pilot observational study, we observed no significant differences in cognition at baseline or 3 months between SAVR and TAVR groups.

Concepts for brain aging: resistance, resilience, reserve, and compensation.

A primary goal of research in cognitive impairment and dementia is to understand how some individuals retain sufficient cognitive function for a fulfilling life while many others are robbed of their independence, sometimes their essence, in the last years and decades of life. In this commentary, we propose operational definitions of the types of factors that may help individuals retain cognitive function with aging. We propose operational definitions of resistance, resilience, reserve, with an eye toward how these may be measured and interpreted, and how they may enable research aimed at prevention. With operational definitions and quantification of resistance, resilience, and reserve, a focused analytic search for their determinants and correlates can be undertaken. This approach, essentially a search to identify protective risk factors and their mechanisms, represents a relatively unexplored pathway toward the identification of candidate preventive interventions.

Distinctive Neurochemistry in Alzheimer's Disease via 7 T In Vivo Magnetic Resonance Spectroscopy.

This study's objective was to increase understanding of biological mechanisms underlying clinical Alzheimer's disease (AD) by noninvasively measuring an expanded neurochemical profile and exploring how well this advanced technology distinguishes AD from cognitively normal controls. We measured concentrations of 14 neurochemicals using ultra-high field (7 T) ultra-short echo time (8 ms) magnetic resonance spectroscopy (MRS) in 16 participants with mild to moderate clinical AD and 33 age- and gender-matched control participants. MRS was localized to the posterior cingulate cortex (PCC), a region known to be impacted by AD, and the occipital cortex (OCC), a control region. Participants with AD were recruited from dementia specialty clinics. Concentration of the antioxidant ascorbate was higher (p < 0.0007) in both brain regions. Concentrations of the glial marker myo-inositol and the choline-containing compounds involved in membrane turnover were higher (p≤0.0004) in PCC of participants with AD. Ascorbate and myo-inositol concentrations were strongly associated, especially in the PCC. Random forests, using the 14 neurochemicals in the two regions, distinguished participants with AD from controls: same-sample sensitivity and specificity were 88% and 97%, respectively, though out-of-sample-values would be lower. Ultra-high field ultra-short echo time MRS identified the co-occurrence of elevated ascorbate and myo-inositol in the PCC as markers that distinguish participants with mild to moderate AD from controls. While elevated myo-inositol may be a surrogate marker of neuroinflammation, the unexpected elevation of the antioxidant ascorbate may reflect infiltration of ascorbate-rich leukocytes.

TDP-43 Neuropathologic Associations in the Nun Study and the Honolulu-Asia Aging Study.

Transactive response binding protein-43 (TDP-43) cytoplasmic neuronal and glial aggregates (pathologic TDP-43) have been described in multiple brain diseases. We describe the associations between neuropathologically confirmed TDP-43 and cognition in two population-based cohorts: the Nun Study (NS) and the Honolulu-Asia Aging Study (HAAS). In the HAAS, there was a significant association between hippocampal sclerosis (HS) and TDP-43 (OR = 11.04, p < 0.0001, 95% CI 3.57-34.13). In the NS, there were significant associations between TDP-43 and HS (OR = 16.44, p > 0.001 95%, CI 7.10-38.00) and Alzheimer's disease (AD) severity (OR = 1.74, p = 0.009, 95% CI 1.15-2.64). When cognitive scores were added to the model, HS remained significant but the other variables were not. When HS was removed from the model, the overall model remained significant and the associations between cognitive performance and TDP-43 (OR = 2.11, p = 0.022, 95% CI 1.11-4.02) were significant. In the NS, there was a significant association between cognitive performance and TDP-43 (OR 1.94 p = 0.005, 95% CI 1.22-3.09) (HS remained significant, but AD did not). When HS was removed from the model, only CERAD was significant (OR = 2.43 p < 0.001, 95% CI 1.58-3.74). These results support a consistent association between pathologic TDP-43, HS, and the development of cognitive impairment in two large studies of brain aging, while the relationship between AD pathology and TDP-43 may vary according to cohort-specific features.

Altered macromolecular pattern and content in the aging human brain.

The resonances originating from proteins underlie those of metabolites in brain 1 H nuclear magnetic resonance (NMR) spectra. These resonances have different physical properties from those of metabolites, such as shorter T1 and T2 relaxation time constants. The age dependence of the macromolecular pattern and content in the human brain was investigated with a focus on adults over 66 years of age using ultrahigh-field in vivo magnetic resonance spectroscopy. Eighteen young and 23 cognitively normal older adults were studied at 7 T. Metabolite spectra were acquired in the occipital cortex and the posterior cingulate cortex with single-voxel stimulated echo acquisition mode (STEAM) spectroscopy in 14 young and 20 older adults. Macromolecular spectra were acquired in the occipital cortex using an inversion recovery STEAM sequence in four young and three older adults. The macromolecular pattern was apparent over the 0.5-4.5-ppm range in the inversion recovery spectra and the 0.5-2-ppm range in the metabolite spectra. Macromolecular content was quantified from metabolite spectra using LCModel and from inversion recovery spectra using integration. Age-associated differences in the macromolecular pattern were apparent via both types of spectra, with the largest difference observed for the 1.7- and 2-ppm macromolecular resonances. A higher macromolecular content was observed in the older adults for both brain regions. Age-specific macromolecular spectra are needed when comparing metabolite spectra from subjects of differing ages because of age-associated differences in macromolecular pattern. Age-associated pattern and content differences may provide information about the aging process.

Physical Activity Interventions in Preventing Cognitive Decline and Alzheimer-Type Dementia: A Systematic Review.

Background: The prevalence of cognitive impairment and dementia is expected to increase dramatically as the population ages, creating burdens on families and health care systems. Purpose: To assess the effectiveness of physical activity interventions in slowing cognitive decline and delaying the onset of cognitive impairment and dementia in adults without diagnosed cognitive impairments. Data Sources: Several electronic databases from January 2009 to July 2017 and bibliographies of systematic reviews. Study Selection: Trials published in English that lasted 6 months or longer, enrolled adults without clinically diagnosed cognitive impairments, and compared cognitive and dementia outcomes between physical activity interventions and inactive controls. Data Extraction: Extraction by 1 reviewer and confirmed by a second; dual-reviewer assessment of risk of bias; consensus determination of strength of evidence. Data Synthesis: Of 32 eligible trials, 16 with low to moderate risk of bias compared a physical activity intervention with an inactive control. Most trials had 6-month follow-up; a few had 1- or 2-year follow-up. Evidence was insufficient to draw conclusions about the effectiveness of aerobic training, resistance training, or tai chi for improving cognition. Low-strength evidence showed that multicomponent physical activity interventions had no effect on cognitive function. Low-strength evidence showed that a multidomain intervention comprising physical activity, diet, and cognitive training improved several cognitive outcomes. Evidence regarding effects on dementia prevention was insufficient for all physical activity interventions. Limitation: Heterogeneous interventions and cognitive test measures, small and underpowered studies, and inability to assess the clinical significance of cognitive test outcomes. Conclusion: Evidence that short-term, single-component physical activity interventions promote cognitive function and prevent cognitive decline or dementia in older adults is largely insufficient. A multidomain intervention showed a delay in cognitive decline (low-strength evidence). Primary Funding Source: Agency for Healthcare Research and Quality.

Does Cognitive Training Prevent Cognitive Decline?: A Systematic Review.

Background: Structured activities to stimulate brain function-that is, cognitive training exercises-are promoted to slow or prevent cognitive decline, including dementia, but their effectiveness is highly debated. Purpose: To summarize evidence on the effects of cognitive training on cognitive performance and incident dementia outcomes for adults with normal cognition or mild cognitive impairment (MCI). Data Sources: Ovid MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and PsycINFO through July 2017, supplemented by hand-searches. Study Selection: Trials (published in English) lasting at least 6 months that compared cognitive training with usual care, waitlist, information, or attention controls in adults without dementia. Data Extraction: Single-reviewer extraction of study characteristics confirmed by a second reviewer; dual-reviewer risk-of-bias assessment; consensus determination of strength of evidence. Only studies with low or medium risk of bias were analyzed. Data Synthesis: Of 11 trials with low or medium risk of bias, 6 enrolled healthy adults with normal cognition and 5 enrolled adults with MCI. Trainings for healthy older adults were mostly computer based; those for adults with MCI were mostly held in group sessions. The MCI trials used attention controls more often than trials with healthy populations. For healthy older adults, training improved cognitive performance in the domain trained but not in other domains (moderate-strength evidence). Results for populations with MCI suggested no effect of training on performance (low-strength and insufficient evidence). Evidence for prevention of cognitive decline or dementia was insufficient. Adverse events were not reported. Limitation: Heterogeneous interventions and outcome measures; outcomes that mostly assessed test performance rather than global function or dementia diagnosis; potential publication bias. Conclusion: In older adults with normal cognition, training improves cognitive performance in the domain trained. Evidence regarding prevention or delay of cognitive decline or dementia is insufficient. Primary Funding Source: Agency for Healthcare Research and Quality.

Pharmacologic Interventions to Prevent Cognitive Decline, Mild Cognitive Impairment, and Clinical Alzheimer-Type Dementia: A Systematic Review.

Background: Optimal treatment to prevent or delay cognitive decline, mild cognitive impairment (MCI), or dementia is uncertain. Purpose: To summarize current evidence on the efficacy and harms of pharmacologic interventions to prevent or delay cognitive decline, MCI, or dementia in adults with normal cognition or MCI. Data Sources: Several electronic databases from January 2009 to July 2017, bibliographies, and expert recommendations. Study Selection: English-language trials of at least 6 months' duration enrolling adults without dementia and comparing pharmacologic interventions with placebo, usual care, or active control on cognitive outcomes. Data Extraction: Two reviewers independently rated risk of bias and strength of evidence; 1 extracted data, and a second checked accuracy. Data Synthesis: Fifty-one unique trials were rated as having low to moderate risk of bias (including 3 that studied dementia medications, 16 antihypertensives, 4 diabetes medications, 2 nonsteroidal anti-inflammatory drugs [NSAIDs] or aspirin, 17 hormones, and 7 lipid-lowering agents). In persons with normal cognition, estrogen and estrogen-progestin increased risk for dementia or a combined outcome of MCI or dementia (1 trial, low strength of evidence); high-dose raloxifene decreased risk for MCI but not for dementia (1 trial, low strength of evidence); and antihypertensives (4 trials), NSAIDs (1 trial), and statins (1 trial) did not alter dementia risk (low to insufficient strength of evidence). In persons with MCI, cholinesterase inhibitors did not reduce dementia risk (1 trial, low strength of evidence). In persons with normal cognition and those with MCI, these pharmacologic treatments neither improved nor slowed decline in cognitive test performance (low to insufficient strength of evidence). Adverse events were inconsistently reported but were increased for estrogen (stroke), estrogen-progestin (stroke, coronary heart disease, invasive breast cancer, and pulmonary embolism), and raloxifene (venous thromboembolism). Limitation: High attrition, short follow-up, inconsistent cognitive outcomes, and possible selective reporting and publication. Conclusion: Evidence does not support use of the studied pharmacologic treatments for cognitive protection in persons with normal cognition or MCI. Primary Funding Source: Agency for Healthcare Research and Quality.

Over-the-Counter Supplement Interventions to Prevent Cognitive Decline, Mild Cognitive Impairment, and Clinical Alzheimer-Type Dementia: A Systematic Review.

Background: Optimal interventions to prevent or delay cognitive decline, mild cognitive impairment (MCI), or dementia are uncertain. Purpose: To summarize the evidence on efficacy and harms of over-the-counter (OTC) supplements to prevent or delay cognitive decline, MCI, or clinical Alzheimer-type dementia in adults with normal cognition or MCI but no dementia diagnosis. Data Sources: Multiple electronic databases from 2009 to July 2017 and bibliographies of systematic reviews. Study Selection: English-language trials of at least 6 months' duration that enrolled adults without dementia and compared cognitive outcomes with an OTC supplement versus placebo or active controls. Data Extraction: Extraction performed by a single reviewer and confirmed by a second reviewer; dual-reviewer assessment of risk of bias; consensus determination of strength of evidence. Data Synthesis: Thirty-eight trials with low to medium risk of bias compared ω-3 fatty acids, soy, ginkgo biloba, B vitamins, vitamin D plus calcium, vitamin C or ß-carotene, multi-ingredient supplements, or other OTC interventions with placebo or other supplements. Few studies examined effects on clinical Alzheimer-type dementia or MCI, and those that did suggested no benefit. Daily folic acid plus vitamin B12 was associated with improvements in performance on some objectively measured memory tests that were statistically significant but of questionable clinical significance. Moderate-strength evidence showed that vitamin E had no benefit on cognition. Evidence about effects of ω-3 fatty acids, soy, ginkgo biloba, folic acid alone or with other B vitamins, ß-carotene, vitamin C, vitamin D plus calcium, and multivitamins or multi-ingredient supplements was either insufficient or low-strength, suggesting that these supplements did not reduce risk for cognitive decline. Adverse events were rarely reported. Limitation: Studies had high attrition and short follow-up and used a highly variable set of cognitive outcome measures. Conclusion: Evidence is insufficient to recommend any OTC supplement for cognitive protection in adults with normal cognition or MCI. Primary Funding Source: Agency for Healthcare Research and Quality.

Resistance to Alzheimer Disease Neuropathologic Changes and Apparent Cognitive Resilience in the Nun and Honolulu-Asia Aging Studies.

Two population-based studies key to advancing knowledge of brain aging are the Honolulu-Asia Aging Study (HAAS) and the Nun Study. Harmonization of their neuropathologic data allows cross comparison, with findings common to both studies likely generalizable, while distinct observations may point to aging brain changes that are dependent on sex, ethnicity, environment, or lifestyle factors. Here, we expanded the neuropathologic evaluation of these 2 studies using revised NIA-Alzheimer's Association guidelines and compared directly the neuropathologic features of resistance and apparent cognitive resilience. There were significant differences in prevalence of Alzheimer disease neuropathologic change, small vessel vascular brain injury, and Lewy body disease between these 2 studies, suggesting that sex, ethnicity, and lifestyle factors may significantly influence resistance to developing brain injury with age. In contrast, hippocampal sclerosis prevalence was very similar, but skewed to poorer cognitive performance, suggesting that hippocampal sclerosis could act sequentially with other diseases to impair cognitive function. Strikingly, despite these observed differences, the proportion of individuals resistant to all 4 diseases of brain or displaying apparent cognitive resilience was virtually identical between HAAS and Nun Study participants. Future in vivo validation of these results awaits comprehensive biomarkers of these 4 brain diseases.

Region-specific aging of the human brain as evidenced by neurochemical profiles measured noninvasively in the posterior cingulate cortex and the occipital lobe using 1H magnetic resonance spectroscopy at 7 T.

The concentrations of fourteen neurochemicals associated with metabolism, neurotransmission, antioxidant capacity, and cellular structure were measured noninvasively from two distinct brain regions using 1H magnetic resonance spectroscopy. Seventeen young adults (age 19-22years) and sixteen cognitively normal older adults (age 70-88years) were scanned. To increase sensitivity and specificity, 1H magnetic resonance spectra were obtained at the ultra-high field of 7T and at ultra-short echo time. The concentrations of neurochemicals were determined using water as an internal reference and accounting for gray matter, white matter, and cerebrospinal fluid content of the volume of interest. In the posterior cingulate cortex (PCC), the concentrations of neurochemicals associated with energy (i.e., creatine plus phosphocreatine), membrane turnover (i.e., choline containing compounds), and gliosis (i.e., myo-inositol) were higher in the older adults while the concentrations of N-acetylaspartylglutamate (NAAG) and phosphorylethanolamine (PE) were lower. In the occipital cortex (OCC), the concentration of N-acetylaspartate (NAA), a marker of neuronal viability, concentrations of the neurotransmitters Glu and NAAG, antioxidant ascorbate (Asc), and PE were lower in the older adults while the concentration of choline containing compounds was higher. Altogether, these findings shed light on how the human brain ages differently depending on region.

Quantitative Comparison of Dense-Core Amyloid Plaque Accumulation in Amyloid-ß Protein Precursor Transgenic Mice.

There exist several dozen lines of transgenic mice that express human amyloid-ß protein precursor (AßPP) with Alzheimer's disease (AD)-linked mutations. AßPP transgenic mouse lines differ in the types and amounts of Aß that they generate and in their spatiotemporal patterns of expression of Aß assemblies, providing a toolkit to study Aß amyloidosis and the influence of Aß aggregation on brain function. More complete quantitative descriptions of the types of Aß assemblies present in transgenic mice and in humans during disease progression should add to our understanding of how Aß toxicity in mice relates to the pathogenesis of AD. Here, we provide a direct quantitative comparison of amyloid plaque burdens and plaque sizes in four lines of AßPP transgenic mice. We measured the fraction of cortex and hippocampus occupied by dense-core plaques, visualized by staining with Thioflavin S, in mice from young adulthood through advanced age. We found that the plaque burdens among the transgenic lines varied by an order of magnitude: at 15 months of age, the oldest age studied, the median cortical plaque burden in 5XFAD mice was already ∼4.5 times that of 21-month-old Tg2576 mice and ∼15 times that of 21-24-month-old rTg9191 mice. Plaque-size distributions changed across the lifespan in a line- and region-dependent manner. We also compared the dense-core plaque burdens in the mice to those measured in a set of pathologically-confirmed AD cases from the Nun Study. Cortical plaque burdens in Tg2576, APPSwePS1ΔE9, and 5XFAD mice eventually far exceeded those measured in the human cohort.

Neuropathologic comorbidity and cognitive impairment in the Nun and Honolulu-Asia Aging Studies.

OBJECTIVE: To examine frequencies and relationships of 5 common neuropathologic abnormalities identified at autopsy with late-life cognitive impairment and dementia in 2 different autopsy panels. METHODS: The Nun Study (NS) and the Honolulu-Asia Aging Study (HAAS) are population-based investigations of brain aging that included repeated cognitive assessments and comprehensive brain autopsies. The neuropathologic abnormalities assessed were Alzheimer disease (AD) neuropathologic changes, neocortical Lewy bodies (LBs), hippocampal sclerosis, microinfarcts, and low brain weight. Associations with screening tests for cognitive impairment were examined. RESULTS: Neuropathologic abnormalities occurred at levels ranging from 9.7% to 43%, and were independently associated with cognitive impairment in both studies. Neocortical LBs and AD changes were more frequent among the predominantly Caucasian NS women, while microinfarcts were more common in the Japanese American HAAS men. Comorbidity was usual and very strongly associated with cognitive impairment. Apparent cognitive resilience (no cognitive impairment despite Braak stage V) was strongly associated with minimal or no comorbid abnormalities, with fewer neocortical AD lesions, and weakly with longer interval between final testing and autopsy. CONCLUSIONS: Total burden of comorbid neuropathologic abnormalities, rather than any single lesion type, was the most relevant determinant of cognitive impairment in both cohorts, often despite clinical diagnosis of only AD. These findings emphasize challenges to dementia pathogenesis and intervention research and to accurate diagnoses during life.