Traumatic Brain Injury Characteristics Are Not Related to Neurocognitive Decline in Older Adults: A Nationwide Longitudinal Cohort Study

OBJECTIVE

Evaluate whether traumatic brain injury (TBI) characteristics, age of injury, or recency of injury predicts the course of neurocognitive decline and/or increases conversion rates to mild cognitive impairment (MCI) or dementia.

METHODS

Data were obtained from the National Alzheimer's Coordinating Center for participants 50-85 years old with 3-5 visits from 2015 to 2022, with or without TBI history (TBI+ = 508; TBI- = 2,382). Groups were stratified by self-reported TBI history (i.e., single TBI without loss of consciousness [LOC], single TBI with LOC, multiple TBI without LOC, and multiple TBI with LOC), age of most recent TBI, and recency of TBI. Mixed linear models compared neuropsychological composite trajectories (executive functioning/attention/speed, language, memory, and global), co-varying for age, gender, education, apolipoprotein E4 status, race/ethnicity, and baseline diagnosis (normal aging n = 1,720, MCI n = 749, or dementia n = 417). Logistic binary regression examined MCI/dementia conversion rates.

RESULTS

There was a slightly higher frequency of MCI/dementia in those with multiple TBIs (50% to 60% with and without LOC, compared to 39% with no TBI) at baseline, but longitudinal trajectories were similar. TBI history, age of injury, or recency of injury did not impact neurocognitive trajectories or conversion rates to MCI/dementia (all p's > .01).

CONCLUSIONS

TBI history, regardless of injury characteristics, age of injury, or recency of injury, did not worsen neurocognitive decline or MCI/dementia conversion. Additional longitudinal research in more diverse cohorts with a wider range of TBI severity is needed to evaluate the specific factors and possible mechanisms in which TBI may increase dementia risk.

A novel speech analysis algorithm to detect cognitive impairment in a Spanish population

Objective

Early detection of cognitive impairment in the elderly is crucial for diagnosis and appropriate care. Brief, cost-effective cognitive screening instruments are needed to help identify individuals who require further evaluation. This study presents preliminary data on a new screening technology using automated voice recording analysis software in a Spanish population.

Method

Data were collected from 174 Spanish-speaking individuals clinically diagnosed as cognitively normal (CN, n = 87) or impaired (mild cognitive impairment [MCI], n = 63; all-cause dementia, n = 24). Participants were recorded performing four common language tasks (Animal fluency, alternating fluency [sports and fruits], phonemic "F" fluency, and Cookie Theft Description). Recordings were processed via text-transcription and digital-signal processing techniques to capture neuropsychological variables and audio characteristics. A training sample of 122 subjects with similar demographics across groups was used to develop an algorithm to detect cognitive impairment. Speech and task features were used to develop five independent machine learning (ML) models to compute scores between 0 and 1, and a final algorithm was constructed using repeated cross-validation. A socio-demographically balanced subset of 52 participants was used to test the algorithm. Analysis of covariance (ANCOVA), covarying for demographic characteristics, was used to predict logistically-transformed algorithm scores.

Results

Mean logit algorithm scores were significantly different across groups in the testing sample (p < 0.01). Comparisons of CN with impaired (MCI + dementia) and MCI groups using the final algorithm resulted in an AUC of 0.93/0.90, with overall accuracy of 88.4%/87.5%, sensitivity of 87.5/83.3, and specificity of 89.2/89.2, respectively.

Conclusion

Findings provide initial support for the utility of this automated speech analysis algorithm as a screening tool for cognitive impairment in Spanish speakers. Additional study is needed to validate this technology in larger and more diverse clinical populations.

Identification of Factors in Moderate-Severe TBI Related to a Functional Decline in Cognition Decades After Injury

OBJECTIVE

To investigate whether a functional decline in cognitive activities decades after moderate-to-severe traumatic brain injury (m-sTBI) might relate to injury features and/or lifetime health factors, some of which may emerge as consequences of the injury.

DESIGN

Secondary analysis of the TBI Model Systems National Database, a prospective, multi-center, longitudinal study of patients with m-sTBI.

SETTING

TBI Model Systems Centers.

PARTICIPANTS

Included were 732 participants rated on the cognitive subscale of the Functional Independence Measure (FIM Cognitive), a metric for everyday cognitive skills, across 3 time points out to 20 years (visits at 2-, 10-, and 20-year follow-ups; N=732).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE(S)

FIM Cognitive Scale. Injury characteristics such as timing and features pertaining to severity and health-related factors (eg, alcohol use, socioeconomic status) were examined to discriminate stable from declining participants on the FIM Cognitive Scale using logistic regression.

RESULTS

At 20 years post-injury, there was a low base rate of FIM Cognitive decline (11%, n=78), with most being stable or having meaningful improvement (89%, n=654). Older age at injury, longer duration of post-traumatic amnesia, and presence of repetitive seizures were significant predictors of FIM Cognitive decline in the final model (area under the curve=0.75), while multiple health-related factors that can represent independent co-morbidities or possible consequences of injury were not.

CONCLUSION(S)

The strongest contributors to reported functional decline in cognitive activities later-in-life were related to acute characteristics of m-sTBI and experiencing post-traumatic seizures. Future studies are needed integrating functional with performance-based cognitive assessments to affirm conclusions and identify the timeline and trajectory of cognitive decline.

History of traumatic brain injury does not alter course of neurocognitive decline in older adults with and without cognitive impairment

OBJECTIVE

Traumatic brain injury (TBI) history is associated with dementia risk, but it is unclear whether TBI history significantly hastens neurocognitive decline in older adults.

METHOD

Data were derived from the National Alzheimer's Coordinating Center (NACC) data set. Participants with a history of TBI (TBI +; n = 1,467) were matched to individuals without a history of TBI (TBI-; n = 1,467) based on age (50-97, M = 71.61, SD = 8.40), sex, education, race, ethnicity, cognitive diagnosis, functional decline, number of Apolipoprotein ε4 (APOE ε4) alleles, and number of annual visits (3-6). Mixed linear models were used to assess longitudinal neuropsychological test composite scores of executive functioning/attention/speed, language, and memory in TBI + and TBI- participants. Interactions between TBI and demographics, APOE ε4 status, and cognitive diagnosis were also examined.

RESULTS

Longitudinal neuropsychological functioning did not differ between TBI groups (p's > .001). There was a significant three-way interaction (age, TBI history, time) in language (F[20, 5750.1] = 3.133, p < .001) and memory performance (F[20, 6580.8] = 3.386, p < .001), but post hoc analyses revealed TBI history was not driving this relationship (all p's > .096). No significant interactions were observed between TBI history and sex, education, race/ethnicity, number of APOE ε4 alleles, or cognitive diagnosis (p's > .001).

CONCLUSIONS

Findings suggest TBI history, regardless of demographic factors, APOE ε4 status, or cognitive diagnosis, does not alter the course of neurocognitive functioning later-in-life in older adults with or without cognitive impairment. Future clinicopathological longitudinal studies that well-characterize head injuries and the associated clinical course are needed to help clarify the mechanism in which TBI may increase dementia risk. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A - 156 History of Mild Traumatic Brain Injury Is Not Associated with worse Neuropsychological Functioning in Amnestic Mild Cognitive Impairment

OBJECTIVE

The mechanisms for traumatic brain injury (TBI) being a risk factor for Alzheimer's disease is unclear, and whether mild TBI (mTBI) may relate to decreased neural circuit functioning in the prodromal phase is unknown. This study examined whether a history of mTBI was associated with lower functioning of neural circuits, measured with neuropsychological tasks, in amnestic Mild Cognitive Impairment (aMCI).

METHOD

Twenty older adults (MAge = 71 years; 70% Male; 90% White) with aMCI were recruited to complete a detailed TBI interview and were classified based on the presence (mTBI+ n = 13) or absence (mTBI- n = 7) of past mTBI. Most mTBI+ participants (n = 11) had multiple mTBIs, and on average were 32 years from last injury. A comprehensive neuropsychological assessment was administered, and composite T-scores were calculated for the domains of attention, executive functioning, memory, and language. One-tailed T-tests were conducted to compare the means between groups.

RESULTS

No statistically significant differences (p's = 0.06-0.09) were found between the groups in memory (mTBI+ M = 38.11; mTBI- M = 33.19), executive function (mTBI+ M = 48.79; mTBI- M = 43.09), language (mTBI+ M = 48.12; mTBI- M = 43.09), or attention (mTBI+ M = 40.54; mTBI- M = 35.57). Nonetheless, medium effect sizes were seen for the mTBI+ group performing better than the mTBI- group on all composite scores (Cohen's d = 0.45-0.66).

CONCLUSIONS

A history of mTBI was not associated with poorer neuropsychological performance in aMCI, often a prodromal stage of Alzheimer's disease. While concerns about later-in-life effects from multiple mTBIs is prevalent, repetitive mTBI may not be related to lower neural circuit functioning in aMCI, though further evaluation with larger samples is needed.

A - 20 Do Alzheimer's Disease Biomarkers Impact Normal Pressure Hydrocephalus Lumbar Drain Trial Outcomes

OBJECTIVE

Distinguishing normal pressure hydrocephalus (NPH) from Alzheimer's disease (ad) would aid patient selection for lumbar drain trials (LDT). Cerebrospinal fluid (CSF) ad biomarkers are altered in NPH, limiting interpretation. This study examines the utility of CSF ad biomarkers in predicting gait and cognitive outcomes in patients undergoing LDT.

METHODS

127 patients underwent LDT. CSF ad biomarkers from Mayo Clinic Laboratories (MCL) or Athena Diagnostics were used to classify patients as ad, non-ad, or indeterminate. MCL indeterminate results were further classified as suspected ad, non-ad, or suspected NPH (sNPH) using a derived p-tau threshold (>15 pg/mL & Aß42 <=1026 pg/mL)1. Cognitive improvement was determined using reliable change indices for Trail Making Test A&B and Hopkins Verbal Learning Test-Revised. Physical therapists (PT) utilized the Berg Balance Scale and/or the Timed Up and Go to determine gait improvements. Chi-square tests investigated relationships between diagnostic groups, PT and cognitive improvements, and eventual shunting for the whole sample and then stratified by the two laboratory assays.

RESULTS

The sNPH group had the highest percentage of PT (63%-70%) and cognitive (9% -11%) improvement (see Table 1), while the ad group had the lowest (50% and 3%, respectively). The sNPH group underwent shunting more (56%-68%) compared to the ad and non-ad groups (47%). Relationships, however, were not statistically significant (p > 0.05).

CONCLUSION

Patients with sNPH CSF ad biomarker profiles demonstrated clinically meaningful physical improvements and underwent shunting more frequently than those with ad or non-ad biomarker profiles. This highlights the potential for CSF ad biomarkers in predicting NPH treatment response.

A - 12 Traumatic Brain Injury Characteristics Are Not Related to Neurocognitive Decline in Older Adults: a Nationwide Longitudinal Cohort Study

OBJECTIVE

Evaluate if traumatic brain injury (TBI) characteristics, age of injury, or recency of injury is related to course of neurocognitive decline in aging and/or increases conversion rates to mild cognitive impairment (MCI) or all-cause dementia later in life.

METHODS

Data were obtained from the National Alzheimer's Coordinating Center for participants 50-85 years old with 3 to 5 visits from 2015-2022. Groups were stratified by: 1) self-reported TBI history (No TBI [n = 2382], Single TBI without loss of consciousness [LOC; n = 102], Single TBI w/LOC [n = 228], Multiple TBI without LOC [n = 36], and Multiple TBI w/LOC [n = 115]), 2) age of most recent TBI (No TBI [n = 2382], TBI = 65 years old [n = 76]), and 3) recency of TBI (no TBI [n = 2382], 15 years ago [n = 301]). Mixed linear models compared normed neuropsychological composite trajectories (executive functioning/attention/speed, language, memory, and overall), co-varying for age, gender, education, apolipoprotein E4 status, and baseline diagnosis (normal aging n = 1720, MCI n = 749, or dementia n = 417). Logistic binary regression examined MCI/dementia conversion rates.

RESULTS

Longitudinal neurocognitive trajectories in composite measures were similar among TBI groups (example figure below). Specific TBI history, age of injury, or recency of injury did not impact neurocognitive trajectories or conversion rates to MCI or dementia (all p's > 0.01).

CONCLUSIONS

TBI history, regardless of injury characteristics, age, or recency, did not worsen neurocognitive decline or MCI/dementia conversion. The mechanism and factors that increase dementia risk after TBI are unclear. Additional longitudinal research in carefully designed longitudinal cohorts is needed.

A - 19 Cognitive Test Score Dispersion VS. Traditional Memory Composite Scores: Predicting Mild Cognitive Impairment (MCI) & Dementia among Cognitively Impaired, Not MCI Patients

OBJECTIVE

To compare mild cognitive impairment (MCI) and dementia conversion rates between global neuropsychological dispersion (GD) and traditional memory neuropsychological composite score (MComp) in participants with baseline evidence of cognitive decline but no diagnosis of MCI or dementia.

METHODS

Data from the National Alzheimer's Coordinating Center (NACC) for 364 participants with a CDR of 0.5, no initial diagnosis of MCI or dementia, and five visits were analyzed. GD was the intraindividual standard deviation across baseline normative (NACC norms) neuropsychological performance. MComp was the mean of the four verbal and visual memory normed scores. Multinomial logistic regression models fit statistics compared GD and MComp as predictors of conversion to MCI/dementia, adjusting for age, sex, race, ethnicity, ApoE4 status, and stratified by suspected etiology (Alzheimer's disease [ad] or no-ad). Lower Akaike Information Criteria (AIC) values indicate better model fit and predictions.

RESULTS

37% progressed to MCI, and 47% to dementia by visit 5. 53% of these were suspected to have ad etiology, and 47% non-ad. MComp showed a better fit with significant predictions of MCI and dementia progression in both suspected ad (AIC: 351.77, p < 0.001) or non-ad etiology (AIC: 215.02, p < 0.004), versus GD was only significant for non-ad etiology (AIC: 385.74, p < 0.003). Better memory performance predicted a lower likelihood of conversion to non-ad MCI (B = -0.65, p = 0.003) and non-ad dementia (B = -1.33, p < 0.001). GD predicted eventual progression to non-ad dementia (B = 2.311, p = 0.004), but not non-ad MCI.

CONCLUSION

Traditional memory composite score may be a better predictor of MCI and dementia conversion than cognitive dispersion in individuals with early cognitive decline who do not yet meet MCI criteria.

No association between age beginning tackle football, or years played and neurocognitive performance later-in-life among older National Football League retirees

OBJECTIVE

In a retrospective cohort, we evaluated whether age beginning tackle football (ABTF) and more total years of playing football (TYPF) were associated with worse later-in-life neuropsychological change among older retired National Football League (NFL) players.

METHOD

Participants were 19 older NFL retirees aged 54-79, including 12 who returned for follow-up evaluation 15-51 months later. Mixed-linear models evaluated the association between ABTF/TYFP and baseline neuropsychological composite scores (executive functioning/attention/speed, language, memory), and neuropsychological composites over time.

RESULTS

ABTF and TYPF were not significantly associated with neuropsychological composites at baseline or over time (all p's > .05). There were no significant differences in neuropsychological performance between those ABTF <12 and ≥ 12 years old (all p's ≥ .475) or between those with TYPF <19 or ≥ 19 years played (median split; all p's ≥ .208).

CONCLUSIONS

Preliminary findings suggest that ABTF and TYPF does not worsen neurocognitive decline later-in-life among older NFL retirees.

Impact of word properties on list learning: An explanatory item analysis

OBJECTIVE

A variety of factors affect list learning performance and relatively few studies have examined the impact of word selection on these tests. This study examines the effect of both language and memory processing of individual words on list learning.

METHOD

Item-response data from 1,219 participants, Mage = 74.41 (SD = 7.13), Medu = 13.30 (SD = 2.72), in the Harmonized Cognitive Assessment Protocol were used. A Bayesian generalized (non)linear multilevel modeling framework was used to specify the measurement and explanatory item-response theory models. Explanatory effects on items due to learning over trials, serial position of words, and six word properties obtained through the English Lexicon Project were modeled.

RESULTS

A two parameter logistic (2PL) model with trial-specific learning effects produced the best measurement fit. Evidence of the serial position effect on word learning was observed. Robust positive effects on word learning were observed for body-object integration while robust negative effects were observed for word frequency, concreteness, and semantic diversity. A weak negative effect of average age of acquisition and a weak positive effect for the number of phonemes in the word were also observed.

CONCLUSIONS

Results demonstrate that list learning performance depends on factors beyond the repetition of words. Identification of item factors that predict learning could extend to a range of test development problems including translation, form equating, item revision, and item bias. In data harmonization efforts, these methods can also be used to help link tests via shared item features and testing of whether these features are equally explanatory across samples. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A Critical Review of Neuropsychological Actuarial Criteria for Mild Cognitive Impairment

BACKGROUND

The concept of mild cognitive impairment (MCI) has evolved since its original conception. So, too, have MCI diagnostic methods, all of which have varying degrees of success in identifying individuals at risk of conversion to dementia. The neuropsychological actuarial method is a straightforward diagnostic approach that has shown promise in large datasets in identifying individuals with MCI who are likely to have progressive courses. This method has been increasingly applied in various iterations and samples, raising questions of how best to apply this method and when caution should be used.

OBJECTIVE

Our objective was to review the literature investigating use of the neuropsychological actuarial method to diagnose MCI to identify strengths and weaknesses of this approach, as well as highlight areas for further research.

METHODS

Databases PubMed and PsychInfo were systematically searched for studies that compared the neuropsychological actuarial method to some other diagnostic method.

RESULTS

We identified 13 articles and extracted relevant study characteristics and findings. Existing literature was reviewed and integrated, with focus on the neuropsychological actuarial method's performance relative to existing diagnostic methods/criteria as well as associations with longitudinal outcomes and biomarkers. Tables with pertinent methodological information and general findings are also provided.

CONCLUSION

The neuropsychological actuarial method to diagnose MCI has shown utility some in large-scale homogenous databases compared to research criteria. However, its standing relative to consensus diagnostic methods is unclear, and emerging evidence suggests the neuropsychological actuarial method may be more prone to diagnostic errors in more demographically diverse populations.

The Spectrum of Alzheimer-Type Pathology in Cognitively Normal Individuals

BACKGROUND

The strongest risk factor for the development of Alzheimer's disease (AD) is age. The progression of Braak stage and Thal phase with age has been demonstrated. However, prior studies did not include cognitive status.

OBJECTIVE

We set out to define normative values for Alzheimer-type pathologic changes in individuals without cognitive decline, and then define levels that would qualify them to be resistant to or resilient against these changes.

METHODS

Utilizing neuropathology data obtained from the National Alzheimer's Coordinating Center (NACC), we demonstrate the age-related progression of Alzheimer-type pathologic changes in cognitively normal individuals (CDR = 0, n = 542). With plots generated from these data, we establish standard lines that may be utilized to measure the extent to which an individual's Alzheimer-type pathology varies from the estimated normal range of pathology.

RESULTS

Although Braak stage and Thal phase progressively increase with age in cognitively normal individuals, the Consortium to Establish a Registry for Alzheimer's Disease neuritic plaque score and Alzheimer's disease neuropathologic change remain at low levels.

CONCLUSION

These findings suggest that an increasing burden of neuritic plaques is a strong predictor of cognitive decline, whereas, neurofibrillary degeneration and amyloid-β (diffuse) plaque deposition, both to some degree, are normal pathologic changes of aging that occur in almost all individuals regardless of cognitive status. Furthermore, we have defined the amount of neuropathologic change in cognitively normal individuals that would qualify them to be "resilient" against the pathology (significantly above the normative values for age, but still cognitively normal) or "resistant" to the development of pathology (significantly below the normative values for age).

Neurocognitive outcomes of older National Football League retirees

OBJECTIVE

Determine if head-injury exposure relates to later-in-life cognitive decline in older National Football League (NFL) retirees.

METHOD

NFL retirees (aged 50+) with or without cognitive impairment underwent baseline (n = 53) and follow-up (n = 29; 13-59 months later) neuropsychological evaluations. Cognitively normal (CN) retirees (n = 26) were age- and education-matched to healthy controls (n = 26). Cognitively impaired (CI) retirees with mild cognitive impairment or dementia (n = 27) were matched to a clinical sample (CS) by age, sex, education, and diagnosis (n = 83). ANOVAs compared neuropsychological composites at baseline and over time between retirees and their matched groups. Regression models evaluated whether concussions, concussions with loss of consciousness (LOC), or games played predicted neuropsychological functioning.

RESULTS

At baseline, CN retirees had slightly worse memory than controls (M_{CN retirees} = 50.69, SE_{CN retirees} = 1.320; M_{Healthy controls} = 57.08, SE_{Healthy controls} = 1.345; p = 0.005). No other group diferences were observed, and head-injury exposure did not predict neurocognitive performance at baseline or over time.

CONCLUSIONS

Head-injury exposure was not associated with later-in-life cognition, regardless of cognitive diagnosis. Some retirees may exhibit lower memory scores compared to age-matched peers, though this is of unclear clinical significance.

A-4 Executive Functioning Is an Important Predictor of Life Expectancy in Those with All-Cause Dementia

Objective: Neuropsychiatric, functional, motor, and demographic factors have been associated with life expectancy (LE) in those with dementia. Recent findings suggested cognition (assessed by the Mini-Mental State Exam [MMSE]) to be the strongest predictor of LE in Alzheimer’s disease (ad; Schaffert et al., 2022). We evaluated if more detailed neuropsychological scores predict LE in a larger sample of individuals with all-cause dementia.

Method: Participants were 4090 deceased individuals (Mage = 74.5, Meducation = 14.8, Male = 44%, White = 90%, Non-Hispanic = 96%) with all-cause dementia (at visit 1, ad = 78%) from the National Alzheimer’s Coordinating Center. Three index scores [executive function/speed/attention (EFAS), language, memory] were calculated from NACC’s neuropsychological batteries. Variables (from visit 1) were entered into a forward regression model (p &lt; 0.001 as point-of-entry) to predict days of LE, and included: age, gender, race (white/non-white), ethnicity (Hispanic/Non-Hispanic), diagnosis (ad/non-ad), abnormal neurological exam (yes/no), Functional Activities Questionnaire (FAQ, total score), Neuropsychiatric Inventory Questionnaire (NPI-Q, total score), MMSE, and EFAS, language, and memory composite Z-scores.

Results: Performance on the EFAS composite explained the most variance in LE (R2 = 0.065), followed by age (R2 = 0.044), diagnosis (R2 = 0.023), FAQ (R2 = 0.016), gender (R2 = 0.012), abnormal neurological exam (R2 = 0.006), NPI-Q (R2 = 0.004), language abilities (R2 = 0.003), and Hispanic ethnicity (R2 = 0.003). Plus/minus one Z-score on the EFAS composite predicted 158 days of LE, and each year of age predicted 27 days of LE.

Conclusions: EFAS performance and age explained &gt;10% of LE variance. The MMSE failed to predict LE in this model that included more detailed neuropsychological data. EFAS impairment may be a more important predictor of LE compared to other neurocognitive domains and cognitive screeners.

A-1 Comparison of Consensus and Actuarial Diagnosis of MCI in Hispanic and non-Hispanic Samples

Objective: The Jak/Bondi actuarial method has been found to be superior to consensus diagnosis in identifying MCI in some but not all populations and may not perform as well in diverse samples. In this study, diagnostic agreement between actuarial and clinical consensus methods was examined by ethnic group in the heavily Hispanic/Latinx Texas Alzheimer’s Research and Care Consortium (TARCC) cohort.

Method: TARCC participants with consensus diagnoses of NC and MCI at baseline (n = 1011; 66.47% female; 49.75% Hispanic; Mage = 67.28; Medu = 13.21) were reclassified via actuarial criteria of two failed tests (&gt;1 SD below normative [MOANS in TARCC] mean) in one cognitive domain OR one failed test in 3+ cognitive domains. Chi square analyses investigated diagnostic agreement and test fail rates by ethnicity.

Results: Diagnostic agreement significantly differed between ethnic groups (Cramer’s V = 0.42). 57% of the Hispanic consensus-NC group were relabeled as actuarial-MCI while just 12% of the consensus-NC non-Hispanic sample were classified as actuarial-MCI. The non-Hispanic consensus-MCI sample was more likely to be reclassified as actuarial-NC (47% reclassified). Failure rates were significantly higher for the Hispanic group on 8 of 10 neuropsychological tests (Cramer’s V = 0.106–0.542).

Conclusions: The Jak/Bondi MCI actuarial method could be prone to false-positive errors in Hispanic/Latinx samples, based on these findings in a significantly more diverse cohort than previously studied. Because the actuarial method relies on normed scores, its application may be more difficult in populations for which adequate norms are still being developed. Further research exploring use of “robust” norms or updated Hispanic/Latinx norms (e.g., NP-NUMBRS) when applying the Jak/Bondi method is needed.

A-10 Influence of Different Normative Reference Standards among Cognitively Normal Former NFL Players

Purpose: Demographic adjustments (e.g., age, sex, race/ethnicity) to neuropsychological tests can assist clinical interpretation and avoid false-positive diagnoses of cognitive impairment. The issue of “race” as a criterion for normative adjustment has been highlighted in recent cases among former NFL players. We examined the impact of different normative reference comparisons on neuropsychological scores among cognitively normal Black and White NFL retirees. Methods: Cognitively normal Black (n = 20) and White (n = 20) retirees were age- and education-matched. Measures of attention (Digit Span), processing speed (Coding, TMTA), memory (ROCFT, CVLT), language (FAS, Animals, BNT), and executive function (TMTB) were examined. Independent samples t-tests (using p &lt; 0.01) were conducted between raw and normative scores of Black and White retirees that adjusted for 1) age/education (Mitrushina); 2) age/education/sex (NACC); and 3) age/education/sex/race (Heaton, MOANS/MOAANS). An additional ANCOVA evaluated group differences controlling for baseline estimated IQ. Results: Raw scores differed between groups on TMTB, Coding, and BNT. Mitrushina normative data showed differences on TMTB (p = 0.007) and BNT (p &lt; 0.001). NACC normative data showed differences on the BNT (p &lt; 0.001). ANCOVA (controlling for IQ) of raw scores between groups differed on the BNT (p = 0.002). Heaton and MOANS/MOAANS normative scores did not reveal differences between groups on any test. Conclusions: As expected, the use of different neuropsychological norms influences findings across different sociodemographic groups to various degrees, depending on the test. The underlying contributors to group differences using “race” as a proxy need to be disentangled and understood. Cautious use of demographically-adjusted norms as interpretive guidelines is warranted until these factors are identified.

Predictors of Life Expectancy in Autopsy-Confirmed Alzheimer's Disease

BACKGROUND

Life expectancy (LE) following Alzheimer's disease (AD) is highly variable. The literature to date is limited by smaller sample sizes and clinical diagnoses.

OBJECTIVE

No study to date has evaluated predictors of AD LE in a retrospective large autopsy-confirmed sample, which was the primary objective of this study.

METHODS

Participants (≥50 years old) clinically and neuropathologically diagnosed with AD were evaluated using National Alzheimer's Coordinating Center (N = 1,401) data. Analyses focused on 21 demographic, medical, neuropsychiatric, neurological, functional, and global cognitive predictors of LE at AD dementia diagnosis. These 21 predictors were evaluated in univariate analyses. Variables found to be significant were then entered into a forward multiple regression. LE was defined as months between AD diagnosis and death.

RESULTS

Fourteen predictors were significant in univariate analyses and entered into the regression. Seven predictors explained 27% of LE variance in 764 total participants. Mini-Mental State Examination (MMSE) score was the strongest predictor of LE, followed by sex, age, race/ethnicity, neuropsychiatric symptoms, abnormal neurological exam results, and functional impairment ratings. Post-hoc analyses revealed correlations of LE were strongest with MMSE ≤12.

CONCLUSION

Global cognitive functioning was the strongest predictor of LE following diagnosis, and AD patients with severe impairment had the shortest LE. AD patients who are older, male, white, and have more motor symptoms, functional impairment, and neuropsychiatric symptoms were also more likely have shorter LE. While this model cannot provide individual prognoses, additional studies may focus on these variables to enhance predictions of LE in patients with AD.

Mild Traumatic Brain Injury Is Related to Elevated Cerebrospinal Fluid Tau in Alzheimer's Disease Dementia

Few studies have examined an association between mild traumatic brain injury (mTBI) and Alzheimer's disease (AD). For this reason, we compared an AD dementia group with an mTBI history (n = 10) to a matched AD control group (n = 20) on measures of cognitive function, cerebral glucose metabolism, and markers of amyloid and tau deposition. Only a trend and medium-to-large effect size for higher phosphorylated and total tau was identified for the mTBI group. A history of mTBI may be associated with greater tau in AD, indicating a potential pathway for increasing risk for AD, though further evaluation with larger samples is needed.

A-3 History of Traumatic Brain Injury and the Course of Neuropsychiatric Symptoms among those with Autopsy-Confirmed Alzheimer’s Disease

Objective

We explored the course of neuropsychiatric symptoms (NPS) in autopsy-confirmed Alzheimer’s disease (ad) subjects with and without a history of TBI (TBI+ vs. TBI-), expecting that TBI history may be associated with NPS severity over time.

Method

Data from 1532 individuals (age 50+) with autopsy-confirmed ad were obtained from the National Alzheimer’s Coordinating Center (Mean visits = 3.69). Those with other tau pathology and significant Lewy pathology were removed. Neuropsychiatric Inventory Questionnaire (NPI-Q) and the 15-item Geriatric Depression Scale (GDS) scores were used to examine NPS. Multilevel zero-inflated binomial regression models assessed if NPS severity differed between TBI+ (N = 154) and TBI- (N = 1378) groups over time. Covariates included: years from baseline visit, demographics, MMSE, Functional Activities Questionnaire score, and psychotropic treatment.

Results

The groups did not differ at baseline in NPI-Q (p = 0.36) or GDS (p = 0.07) scores. NPI-Q scores mildly decreased in the TBI+ group (trend = −0.03), whereas the TBI- group remained stable over time (trend = 0.001), 95% CI for the trend [0.01, 0.07]. GDS scores increased more rapidly in the TBI+ group (trend = 0.08) than the TBI- group (trend = 0.02), 95% CI for the trend [0.02, 0.10].

Conclusions

This preliminary study suggests that NPS course in ad may differ depending on TBI history, though effect sizes were small. Over the course of ad, individuals with a history of TBI may experience less NPS overall (as measured by NPI-Q scores) but may experience marginally more depressive symptoms (as measured by GDS scores). Future investigations evaluating the relationship between TBI and the course of neurodegenerative disease are needed.

A-1 Neuropsychiatric Symptoms over Time in Autopsy-Confirmed Alzheimer’s Disease, Lewy Body Disease, and Mixed Pathology

Objective

Neuropsychiatric symptoms (NPS) are common in neurodegenerative disease, but longitudinal studies using large autopsy-confirmed samples are lacking. Our primary aim was to investigate progression of NPS over time in autopsy-confirmed Alzheimer’s disease (ad), Lewy body disease (LBD), and mixed (ad+LBD) cohorts.

Methods

Data on individuals (age &gt; =50) with autopsy-confirmed ad (N = 1568), ad+LBD (N = 349), and LBD (N = 142) was obtained from the National Alzheimer’s Coordinating Center (Mean visits = 2.61). Neuropsychiatric Inventory Questionnaire (NPI-Q) and 15-item Geriatric Depression Scale (GDS) scores were used to measure NPS. Multilevel zero-inflated binomial regression models were used to assess if NPI-Q and GDS scores differed among ad, ad+LBD, and LBD groups over time. Covariates included: years from baseline to final visit, cognitive status at baseline (i.e., normal, MCI, or dementia), demographic characteristics, MMSE, Functional Activities Questionnaire, and psychotropic treatment of psychiatric conditions.

Results

Higher NPI-Q and GDS scores were observed at baseline in the LBD group compared to ad (p’s &lt; 0.001). NPI-Q scores increased over time in the LBD group compared to ad+LBD and ad groups (90% CI). GDS scores differed among all groups at baseline (95% CI), with more rapid increase in the LBD group vs. ad and ad+LBD groups.

Conclusions

Overall, the course of NPS differs among disease pathologies. Those with pure LBD appear to have more severe NPS over time compared to those with ad and ad+LBD. Depressive symptoms increased more in LBD and ad+LBD compared to ad over time. Future research examining clinical outcomes related to NPS burden (care needs, caregiver burden, and life expectancy) is needed.

Frequency and Predictors of Traumatic Encephalopathy Syndrome in a Prospective Cohort of Retired Professional Athletes

Traumatic encephalopathy syndrome (TES) is proposed to represent the long-term impact of repetitive head-injury exposure and the clinical manifestation of chronic traumatic encephalopathy (CTE). This study aimed to evaluate the frequency of TES in a cohort of retired professional contact sport athletes, compare the frequency of TES to clinical consensus diagnoses, and identify predictors that increase the likelihood of TES diagnosis. Participants were 85 retired professional contact sport athletes from a prospective cohort at the University of Texas Southwestern Medical Center and the University of Texas at Dallas. Participants ranged in age from 23 to 79 (M = 55.95, SD = 13.82) and obtained 7 to 19 years of education (M = 16.08, SD = 1.03). Retirees were either non-Hispanic white (n = 62) or African-American (n = 23). Retired athletes underwent a standard clinical evaluation, which included a clinical interview, neurological exam, neuroimaging, neuropsychological testing, and consensus diagnosis of normal, mild cognitive impairment, or dementia. TES criteria were applied to all 85 athletes, and frequencies of diagnoses were compared. Fourteen predictors of TES diagnosis were evaluated using binary logistic regressions, and included demographic, neuropsychological, depression symptoms, and head-injury exposure variables. A high frequency (56%) of TES was observed among this cohort of retired athletes, but 54% of those meeting criteria for TES were diagnosed as cognitively normal via consensus diagnosis. Games played in the National Football League (OR = 0.993, p = 0.087), number of concussions (OR = 1.020, p = 0.532), number of concussions with loss of consciousness (OR = 1.141 p = 0.188), and years playing professionally (OR = 0.976, p = 0.627) were not associated with TES diagnosis. Degree of depressive symptomatology, as measured by the total score on the Beck Depression Inventory-II, was the only predictor of TES diagnosis (OR = 1.297, p < 0.001). Our results add to previous findings underscoring the risk for false positive diagnosis, highlight the limitations of the TES criteria in clinical and research settings, and question the relationship between TES and head-injury exposure. Future research is needed to examine depression in retired professional athletes.

A-08 Examination of Three Functional Living Scales Using Item Response Theory Modeling in a Mixed Sample

Objective

Characterize three functional living scales under item response theory and examine these scales for evidence of differential item functioning (DIF) by participant and/or informant ethnicity and education.

Method

Baseline data from 3155 participants [Mage = 70.59(9.55); Medu = 13.3(4.26); 61.72%female] enrolled in the Texas Alzheimer’s Research and Care Consortium with data from the Clinical Dementia Rating Scale (CDR; functional items), Physical Self-Maintenance Scale (PSMS), and Instrumental Activities of Daily Living Scale (IADL) were used. The sample was predominately white (93.94%) and 35.97% identified as Hispanic. Graded response models fit all three tests best. DIF was examined by iteratively dropping item-by-item constraints and then testing model fit.

Results

The CDR demonstrated overall good item functioning with clear separation between all of the rating categories for each item, while the PSMS and IADL did not, suggesting the item ratings should be reconsidered. DIF was observed by ethnicity (Hispanic v. non-Hispanic) and education (separated into low, average, high) for every item on all three scales (all ps ≤ .01 after adjustment for multiple observations). Hispanic ethnicity and higher education subjects were more likely to be rated as more impaired.

Conclusions

Results suggest these three commonly used functional scales have DIF depending on the ethnicity and education of the patient. This finding has implications for understanding functional change in certain populations, particularly the potential for mischaracterization of impairment in minority samples. The finding that individuals with higher education tended to be rated as more functionally impaired warrants further investigation.

A-16 Latent Item Response Theory Regression Using Neuropsychological Tests to Predict Functional Ability

Objective

Examine prediction of functional ability with neuropsychological tests using latent item response theory.

Method

The sample included 3155 individuals (Mage = 69.72, SD = 9.41; Median education =13.15, SD = 4.40; white = 92.81%; female = 62.03%; MCI = 25.13%; Dementia = 28.87%) from the Texas Alzheimer’s Research and Care Consortium who completed functional and cognitive assessments [Mini Mental State Examination (MMSE), Logical Memory (LM), Visual Reproduction (VR), Controlled Oral Word Association Test (COWAT), Trail Making Test (TMT), Boston Naming Test, and Digit Span]. Functional measures [Clinical Dementia Rating Scale, Physical Self Maintenance Scale, and Instrumental Activities of Daily Living)] were combined into a single outcome variable using confirmatory factor analysis. Item response theory (IRT) was used to fit the data, and latent regression to predict the latent trait score using neuropsychological data.

Results

All three functional scales loaded onto a single factor and demonstrated good construct coverage and measurement reliability (Supporting Figure). A graded response IRT model best fit the functional ability composite measure. MMSE (b = −1.08, p &lt; .001), LM II (b = −0.58, p &lt; .001), VR I and II (b = −0.09, p = .02 and b = −0.43, p &lt; .001, respectively), COWAT (b = −0.10, p = .003), and TMT-B (b = −0.30, p &lt; .001) all significantly predicted functional abilities, as did age (b = 0.61, p &lt; .001) and education (b = 0.31, p &lt; .001).

Conclusions

Global cognition, memory and executive function tests predicted functional abilities while attention and language tasks did not. These results suggest that certain neuropsychological tests meaningfully predict functional abilities in elderly cognitively normal and cognitively impaired individuals. Further research is needed to determine whether these cognitive domains are predictive of functional abilities in other clinical disorders.

Clinical and neuropsychological profile of patients with dementia and chronic traumatic encephalopathy

OBJECTIVE

To determine whether subjects with chronic traumatic encephalopathy (CTE) and dementia have distinct clinical features compared to subjects with pathologically confirmed Alzheimer's disease (AD).

METHODS

Among 339 subjects assessed for CTE in the National Alzheimer's Coordinating Center dataset, 6 subjects with CTE and 25 subjects with AD neuropathologic change matched for age (±5 years) and sex were identified. All subjects had a clinical diagnosis of dementia. Neurological examination, neuropsychological testing and emotional/behavioural data were compared between CTE and AD subjects at the time of dementia diagnosis and last clinical visit near death.

RESULTS

A history of traumatic brain injury with loss of consciousness (LOC) was reported in one CTE and one AD subject; information about injuries without LOC or multiple injuries was unavailable. CTE and AD subjects did not differ significantly at the time of diagnosis or last visit on the Unified Parkinson's Disease Rating Scale-Motor Exam, global measures of cognitive functioning (Mini-Mental State Exam and Clinical Dementia Rating Scale), emotional/behaviour symptoms as assessed with the Neuropsychiatric Inventory questionnaire or across neuropsychological measures. All CTE participants had co-occurring neuropathologic processes, including AD and most had TAR DNA-binding protein 43 (TDP-43) neuropathology.

CONCLUSIONS

CTE pathology was rare in a large multicentre national dataset, and when present, was accompanied by AD and TDP-43 pathologies. CTE was not associated with a different clinical presentation from AD or with greater cognitive impairment or neurobehavioral symptoms. These findings suggest that CTE may not have a distinct clinical profile when other neuropathologic processes are coexistent with CTE pathology.

Risk factors for earlier dementia onset in autopsy-confirmed Alzheimer's disease, mixed Alzheimer's with Lewy bodies, and pure Lewy body disease

INTRODUCTION

Clinical Alzheimer's disease (AD) and dementia with Lewy bodies often have mixed AD and Lewy pathology, making it difficult to delineate risk factors.

METHODS

Six risk factors for earlier dementia onset due to autopsy-confirmed AD (n = 647), mixed AD and Lewy body disease (AD + LBD; n = 221), and LBD (n = 63) were entered into multiple linear regressions using data from the National Alzheimer's Coordinating Center.

RESULTS

In AD and AD + LBD, male sex and apolipoprotein E (APOE) ɛ4 alleles each predicted a 2- to 3-year-earlier onset and depression predicted a 3-year-earlier onset. In LBD, higher education predicted earlier onset and depression predicted a 5.5-year-earlier onset.

DISCUSSION

Male sex and APOE ɛ4 alleles increase risk for earlier dementia onset in AD but not LBD. Depression increases risk for earlier dementia onset in AD, LBD, and AD + LBD, but evaluating the course, treatment, and severity is needed in future studies.

Neuropsychological functioning in ageing retired NFL players: a critical review

Recent discovery of chronic traumatic encephalopathy in former National Football League (NFL) players has led to a surge of papers investigating cognitive functioning in these former athletes. This critical review of the literature focused on the neuropsychological functioning in these ageing athletes, and included 22 articles published between 2013 and 2019, of which 13 reported on neuroradiological imaging and four focused on dose-response relationships of repetitive head injury on cognitive outcomes. Four studies suggest higher prevalence of MCI and neurodegenerative disease among NFL retirees, although a quantifiable risk and prevalence of cognitive impairment and dementia in these players remains unknown. Decreased verbal memory has been found in some players across multiple studies, though with unknown clinical significance due to small sample sizes, unreported effect sizes, and absence of longitudinal data. Studies investigating a dose-response relationship between cognitive decline and head injury have generated mixed findings utilizing various measures of head injury exposure. Neuroradiological findings are inconsistent, but suggest that some NFL players may be at greater risk for reduced white matter integrity. Future research is needed to understand the relationship between sports-related concussions and the risk of long-term cognitive decline and neurodegenerative disease in ageing NFL players.

Associations of Race-Ethnicity and History of Traumatic Brain Injury With Age at Onset of Alzheimer's Disease

OBJECTIVE

This study examined whether a history of traumatic brain injury (TBI) is associated with age at onset of Alzheimer's disease (AD) in three racial-ethnic groups.

METHODS

Data from 7,577 non-Hispanic Caucasian, 792 African American, and 870 Hispanic participants with clinically diagnosed AD were obtained from the National Alzheimer's Coordinating Center. Participants were categorized by the presence or absence of self-reported remote history of TBI (>1 year before diagnosis of AD) with loss of consciousness (LOC) (TBI+) or no history of TBI with LOC (TBI-). Any group differences in education; sex; APOE ε4 alleles; family history of dementia; or history of depression, stroke, hypertension, hypercholesterolemia, and diabetes were included in analyses of covariance comparing clinician-estimated age at AD symptom onset for the TBI+ and TBI- groups.

RESULTS

AD onset occurred 2.3 years earlier for non-Hispanic Caucasians (F=30.49, df=1, 7,572, p<0.001) and 3.4 years earlier for African Americans (F=5.17, df=1, 772, p=0.023) in the TBI+ group. In the Hispanic cohort, females in the TBI+ group had AD onset 5.6 years earlier, compared with females in the TBI- group (F=6.96, df=1, 865, p=0.008); little difference in age at AD onset was observed for Hispanic males with and without a TBI history.

CONCLUSIONS

A history of TBI with LOC was associated with AD onset 2-3 years earlier in non-Hispanic Caucasians and African Americans and an onset nearly 6 years earlier in Hispanic females; no association was observed in Hispanic males. Further work in underserved populations is needed to understand possible underlying mechanisms for these differences.

Traumatic Brain Injury and Age of Onset of Dementia with Lewy Bodies

BACKGROUND

Traumatic brain injury (TBI) with loss of consciousness (LOC) has been associated with earlier onset of mild cognitive impairment, frontotemporal dementia, Parkinson's disease, and Alzheimer's disease (AD), but has not been examined as a risk factor for earlier onset of dementia with Lewy bodies (DLB).

OBJECTIVE

The purpose of this study was to assess the association between a history of TBI and the age of onset of DLB.

METHOD

Data from 576 subjects with a clinical diagnosis of DLB were obtained from the National Alzheimer's Coordinating Center (NACC). Analyses of Covariance examined whether self-reported history of remote TBI with LOC (i.e., >1 year prior to the first Alzheimer's Disease Center visit) was associated with earlier DLB symptom onset.

RESULTS

Controlling for sex, those with a history of remote TBI had an approximately 1.5-year earlier clinician-estimated age of onset (F = 0.87, p = 0.35) and 0.75-years earlier age of diagnosis (F = 0.14, p = 0.71) of DLB compared to those without a history of TBI, though the differences did not reach statistical significance. Analysis of subjects with autopsy-confirmed diagnoses was underpowered due to the low number of TBI+ subjects.

CONCLUSIONS

Remote TBI with LOC was not significantly associated with DLB onset, despite being a significant risk factor for cognitive decline and earlier age of onset in other neurodegenerative conditions. Replication of these results using a larger cohort of DLB subjects with and without a TBI history who have undergone autopsy is indicated, as our TBI+ subjects did show a slightly earlier onset of about 1.5 years. Further investigations into other potential DLB risk factors are also warranted.

Annualized Decline in Instrumental Activities of Daily Living Is Slower in Hispanics Compared to Non-Hispanics in an Alzheimer’s Disease Sample

Objective

Research examining the course of Alzheimer’s disease (AD) in Hispanics is lacking. This study examined demographic, psychiatric, cognitive, and genetic predictors of longitudinal functional change in Hispanics and non-Hispanics with AD.

Method

Longitudinal change in instrumental activities of daily living (IADL) was examined over 10 years (M = 4.15 years) in 292 subjects (Hispanic = 67, non-Hispanic = 225). All were part of the Texas Alzheimer’s Research & Care Consortium and included those with AD (n = 217) and those with mild cognitive impairment at baseline who progressed to AD at follow-up (n = 75). Baseline comparisons were conducted between ethnic groups for demographics, Geriatric Depression Scale (GDS-30) score, Mini Mental State Examination (MMSE) score, presence of apolipoprotein ɛ4 alleles (APOE4), and annualized IADL change scores and then entered into a multiple linear regression model as predictors of annualized IADL change.

Results

The Hispanic group had significantly more females (χ2 = 5.71, p = .017), lower education [MH = 9.96(4.39), MNH = 15.26(2.70)], higher depression scores [GDS-30; MH = 9.45(5.89), MNH = 5.51(4.29)], lower MMSE scores [MH = 23.31(4.33), MNH = 24.65(3.21)], and slower annualized IADL change [MH = 1.19(1.42), MNH = 2.02(1.60)]. Regression results were significant (F = 3.66, p = .001, R2 = .08 ), with higher baseline MMSE (p = .007) and Hispanic origin (p = .010) predicting slower annualized IADL change. Demographics, APOE4 status, and depression did not significantly predict IADL change.

Conclusions

Higher cognitive functioning at baseline and Hispanic origin was associated with slower functional decline over an average 4-year period of time. Despite having lower MMSE scores at baseline, greater depression, and less education, the Hispanic group had a slower decline in IADLs compared to non-Hispanics. Further research is needed to better understand how/why Hispanic origin is associated with slower functional decline.

Predictors of Life Expectancy After an Alzheimer’s Disease Diagnosis in a National Multi-Center Autopsy-Confirmed Sample

Objective

Life expectancy varies between 3-12 years following the diagnosis of Alzheimer’s disease (AD) and is an important clinical question for patients and families. Current literature is limited by relatively small sample sizes and a reliance on clinical diagnoses. This study sought to evaluate predictors of AD life expectancy in a large autopsy-confirmed sample.

Methods

Baseline data from individuals 50 years and older clinically and neuropathologically diagnosed with AD (N=764) were obtained from the National Alzheimer’s Coordinating Center. Life expectancy was calculated in months from AD diagnosis to death. Nineteen variables (demographic, medical/health, disease severity, and psychiatric) obtained at dementia diagnosis were examined. Variables that showed significant differences in life expectancy using t-tests and Pearson correlations (14 of 19) were then entered into a forward multiple regression.

Results

Seven predictors in the model explained 27% of the variance in life expectancy (F= 40.7, R-squared= 0.267). Lower MMSE scores (β= 0.339, p < .001), male sex (β= -0.144, p < .001), older age (β= -0.130, p < .001), non-Hispanic Caucasian race/ethnicity (β= 0.115, p < .001), greater impairment on the Functional Activities Questionnaire (β= -0.091, p=.042), abnormal neurological/physical exam (β= -0.083, p=.011), and higher Neuropsychiatric Inventory Questionnaire total scores (β= -0.079, p=.016) predicted shorter life expectancy.

Conclusions

Global cognitive impairment, sex, age, race/ethnicity, functional impairment, abnormal neurological exam findings, and psychiatric symptoms explain a significant proportion of life expectancy following an AD diagnosis. Future studies should explore the relationship between life expectancy, specific neurological abnormalities, and psychiatric symptoms. These 7 predictors could potentially be used to predict life expectancy in individuals diagnosed with AD.

Traumatic brain injury history is associated with an earlier age of dementia onset in autopsy-confirmed Alzheimer's disease

OBJECTIVE

To evaluate whether a history of traumatic brain injury (TBI) with reported loss of consciousness (LOC) is a risk factor for earlier onset of Alzheimer's disease (AD) in an autopsy-confirmed sample.

METHOD

Data from 2,133 participants with autopsy-confirmed AD (i.e., at least Braak neurofibrillary tangle stages III to VI and CERAD neuritic plaque score moderate to frequent) were obtained from the National Alzheimer's Coordinating Center (NACC). Participants were categorized by presence/absence of self-reported remote (i.e., >1 year prior to their first Alzheimer's Disease Center visit) history of TBI with LOC (TBI+ vs. TBI-). Analyses of Covariance (ANCOVA) controlling for sex, education, and race compared groups on clinician-estimated age of symptom onset and age of diagnosis.

RESULTS

Average age of onset was 2.34 years earlier (p = .01) for the TBI+ group (n = 194) versus the TBI- group (n = 1900). Dementia was diagnosed on average 2.83 years earlier (p = .002) in the TBI+ group (n = 197) versus the TBI- group (n = 1936). Using more stringent neuropathological criteria (i.e., Braak stages V-VI and CERAD frequent), both age of AD onset and diagnosis were 3.6 years earlier in the TBI+ group (both p's < .001).

CONCLUSIONS

History of TBI with reported LOC appears to be a risk factor for earlier AD onset. This is the first study to use autopsy-confirmed cases, supporting previous investigations that used clinical criteria for the diagnosis of AD. Further investigation as to possible underlying mechanisms of association is needed. (PsycINFO Database Record

Scanning noise microscopy

The paper describes a simple scheme enabling the real-time characterization of fluctuations, e.g., of the conductance in scanning tunneling microscopy. The technique can be used in parallel to other data acquisition, evaluating the rate, the amplitude, and the duty cycle of telegraphic noise in the tunneling current. This kind of scanning probe microscopy allows to evaluate the noise parameters as a function of the average tunneling current, the electron energy, and the lateral position. Images of the noise with Ångstrom spatial resolution are acquired simultaneously to the topographic information providing a direct correlation between the structural information and the noise. The method can be applied to a large variety of systems to monitor dynamics on the nanoscale, e.g., the localization of tunneling current induced switching within a single molecule. Noise spectroscopy may reveal the involved molecular orbitals, even if they cannot be resolved in standard scanning tunneling spectroscopy. As an example we present experimental data of the organic molecule copper phthalocyanine on a Cu(111) surface [J. Schaffert, M. C. Cottin, A. Sonntag, H. Karacuban, C. A. Bobisch, N. Lorente, J.-P. Gauyacq, and R. Möller, Nature Mater. 12, 223-227 (2013)].