The role of oestrogen therapy in reducing risk of Alzheimer's disease: systematic review

BACKGROUND

Studies have shown a relationship between oestrogen and Alzheimer's disease. However, there is neither clear nor strong evidence on the use of oestrogen-only therapy in reducing the risk of Alzheimer's disease.

AIMS

To assess the effects of oestrogen-only therapy on reducing the risk of Alzheimer's disease.

METHOD

Inclusion criteria was determined with the PICO framework. Outcome was cognitive function measured by neuropsychological tests and strict protocols. Exclusion criteria included non-Alzheimer's dementia, progesterone-only therapy and pre-menopausal women. Searches were conducted in nine electronic healthcare databases, last searched in July 2022. Quality assessments conducted on randomised controlled trials (RCTs) were performed with the GRADE assessment, and cohort studies and case-control studies were assessed with the Newcastle-Ottawa Scale. Extracted data were used to analyse participants, interventions and outcomes.

RESULTS

Twenty-four studies satisfied the search criteria (four RCTs, nine cohort studies, 11 case-control studies). Fifteen studies showed positive associations for oestrogen-only therapy reducing the risk of Alzheimer's disease, and the remaining nine found no evidence of association.

CONCLUSIONS

Fifteen studies showed that oestrogen-only therapy effectively reduced the risk of Alzheimer's disease, whereas nine showed no correlation. Studies also investigated oestrogen-related variables such as length of oestrogen exposure, being an apolipoprotein E ε4 carrier and concomitant use of non-steroidal anti-inflammatory drugs, and their role in neuroprotection. This review was limited by the limited ranges of duration of oestrogen treatment and type of oestrogen-only therapy used. In conclusion, oestrogen-only therapy has potential for use in preventing Alzheimer's disease, although current evidence is inconclusive and requires further study.

Cellular Substrates of Functional Network Integration and Memory in Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) patients are at risk of memory deficits, which have been linked to functional network disturbances, particularly of integration of the default mode network (DMN). However, the cellular substrates of functional network integration are unknown. We leverage a unique cross-scale dataset of drug-resistant TLE patients (n = 31), who underwent pseudo resting-state functional magnetic resonance imaging (fMRI), resting-state magnetoencephalography (MEG) and/or neuropsychological testing before neurosurgery. fMRI and MEG underwent atlas-based connectivity analyses. Functional network centrality of the lateral middle temporal gyrus, part of the DMN, was used as a measure of local network integration. Subsequently, non-pathological cortical tissue from this region was used for single cell morphological and electrophysiological patch-clamp analysis, assessing integration in terms of total dendritic length and action potential rise speed. As could be hypothesized, greater network centrality related to better memory performance. Moreover, greater network centrality correlated with more integrative properties at the cellular level across patients. We conclude that individual differences in cognitively relevant functional network integration of a DMN region are mirrored by differences in cellular integrative properties of this region in TLE patients. These findings connect previously separate scales of investigation, increasing translational insight into focal pathology and large-scale network disturbances in TLE.

Measuring reliable change in traumatic brain injury (TBI): The pitfalls of using readily available formulae

Individuals with a traumatic brain injury (TBI) frequently undergo repeat neuropsychological assessments. Reliable change (RC) methodologies based on general population normative data are often used to assess for clinically significant change. The consequence of applying such methodologies to an individual with a TBI needs investigation. The current study tested the validity of readily available formulae in moderate to severe TBI participants who were >2 years postinjury. Participants were administered the Wechsler Adult Intelligence Scale-IV/Wechsler Memory Scale-IV (WAIS/WMS-IV) battery on two occasions across an approximate 1 year interval. Index scores were entered into 10 RC formulae to assess their validity in individuals with a TBI. Findings revealed that the formulae used in the study are relatively interchangeable in regards to WAIS-IV assessment, but that many of the formulae identified statistically unexpected rates of RC change in memory tasks assessed by the WMS-IV. Two formulae that did not contain statistical manipulations for practice effects performed relatively well in regards to memory assessment. Therefore, indiscriminate use of RC formulae could lead to over identifying memory decline in the TBI populations. The results suggest that either Iverson or Jacobson and Truax formulae can be used to assess RC for memory in moderate to severe TBI populations.

Evaluating Mild Cognitive Impairment in Essential Tremor: How Many and Which Neuropsychological Tests?

OBJECTIVES

Essential tremor (ET) confers an increased risk for developing both amnestic and non-amnestic mild cognitive impairment (MCI). Yet, the optimal measures for detecting mild cognitive changes in individuals with this movement disorder have not been established. We sought to identify the cognitive domains and specific motor-free neuropsychological tests that are most sensitive to mild deficits in cognition as defined by a Clinical Dementia Rating (CDR) of 0.5, which is generally associated with a clinical diagnosis of MCI.

METHODS

A total of 196 ET subjects enrolled in a prospective, longitudinal, clinical-pathological study underwent an extensive motor-free neuropsychological test battery and were assigned a CDR score. Logistic regression analyses were performed to identify the neuropsychological tests which best identified individuals with CDR of 0.5 (mild deficits in cognition) versus 0 (normal cognition).

RESULTS

In regression models, we identified five tests in the domains of Memory and Executive Function which best discriminated subjects with CDR of 0.5 versus 0 (86.9% model classification accuracy). These tests were the California Verbal Learning Test II Total Recall, Logical Memory II, Verbal-Paired Associates I, Category Switching Fluency, and Color-Word Inhibition.

CONCLUSIONS

Mild cognitive difficulty among ET subjects is best predicted by combined performance on five measures of memory and executive function. These results inform the nature of cognitive dysfunction in ET and the creation of a brief cognitive battery to assess patients with ET for cognitively driven dysfunction in life that could indicate the presence of MCI. (JINS, 2018, 24, 1084-1098).

Performance Invalidity Base Rates Among Healthy Undergraduate Research Participants

Few studies have examined base rates of suboptimal effort among healthy, undergraduate students recruited for neuropsychological research. An and colleagues (2012, Conducting research with non-clinical healthy undergraduates: Does effort play a role in neuropsychological test performance? Archives of Clinical Neuropsychology, 27, 849-857) reported high rates of performance invalidity (30.8%-55.6%), calling into question the validity of findings generated from samples of college students. In contrast, subsequent studies have reported much lower base rates ranging from 2.6% to 12%. The present study replicated and extended previous work by examining the performance of 108 healthy undergraduates on the Dot Counting Test, Victoria Symptom Validity Test, Word Memory Test, and a brief battery of neuropsychological measures. During initial testing, 8.3% of the sample scored below cutoffs on at least one Performance Validity Test, while 3.7% were classified as invalid at Time 2 (M interval = 34.4 days). The present findings add to a growing number of studies that suggest performance invalidity base rates in samples of non-clinical, healthy college students are much lower than An and colleagues initial findings. Although suboptimal effort is much less problematic than suggested by An and colleagues, recent reports as high as 12% indicate including measures of effort may be of value when using college students as participants. Methodological issues and recommendations for future research are presented.