Sex differences in Alzheimer's disease and other dementias

The art of matching brain tissue from patients and controls for postmortem research

The quality of postmortem research depends strongly on a thorough clinical investigation and documentation of the patient's disorder and therapies. In addition, a systematic and professional neuropathologic investigation of both cases and controls is absolutely crucial. In the experience of the Netherlands Brain Bank (NBB), about 20% of clinical neurologic diagnoses, despite being made in first-rate clinics, have to be revised or require an extra diagnosis after a complete and thorough review by the NBB. The neuropathology examination may reveal for instance that the "controls" already have preclinical neurodegenerative alterations. In postmortem studies the patient and control groups must be matched for as many of the known confounding factors as possible. This is necessary to make the groups as similar as possible, except for the topic being investigated. Confounding factors are present before, during, and after death. They are respectively: (1) genetic background, systemic diseases, duration and gravity of illness, medicines and addictive compounds used, age, sex, gender identity, sexual orientation, circadian and seasonal fluctuations, lateralization; (2) agonal state, stress of dying; and (3) postmortem delay, freezing procedures, fixation and storage time. Consequently, a brain bank should have a large number of controls at its disposal for appropriate matching. If matching fails for some confounders, then their influence may be determined by statistical methods such as analysis of variance or regression models.

Behavioural and Psychological Symptoms of Dementia: Correlates and Impact on Caregiver Distress

Aims

To evaluate the behavioural and psychological symptoms of dementia (BPSD), to determine their correlation with types and stages of dementia and patient demographics, and to assess the impact on caregiver distress.

Methods

This cross-sectional study recruited consecutive dementia patients and caregivers who attended our cognitive clinic. Standard criteria were used to classify types of dementia. BPSD were assessed with the Neuropsychiatric Inventory, and its distress scale was used for caregiver distress.

Results

Of a total 107 patients, nearly all (99.1%) had at least one BPSD; 71% had ≥4 symptoms. Most frequent were apathy and agitation, followed by irritability, sleep and appetite disorders, and mood disorders; disinhibition and euphoria were least frequent. BPSD were less prominent with increasing age; males showed more agitation. Apathy and eating disorders were more prevalent in the rural community. BPSD were highest in frontotemporal dementia (FTD), followed by dementia with Lewy bodies (DLB), and least in vascular dementia. Hallucinations were more common in DLB, aberrant motor behaviour in FTD. All domains of BPSD, except for anxiety and euphoria, were more prominent with increasing severity of dementia. Increasing BPSD (except for euphoria) caused higher caregiver distress.

Conclusion

BPSD are universally present, bear correlates with dementia type and severity, and cause significant caregiver distress.

Decreased risk of dementia in migraine patients with traditional Chinese medicine use: a population-based cohort study

Patients with migraine are reportedly at increased risk of developing dementia. We aimed to investigate the association between traditional Chinese medicine (TCM) use and dementia risk in migraine patients. This longitudinal cohort study used the Taiwanese National Health Insurance Research Database to identify 32,386 diagnosed migraine patients aged 20 years and above who received treatment from 1997 to 2010. To balance comparability between TCM users and non-TCM users, we randomly selected equal numbers from each group, and compared subgroups compiled based on combinations of age, sex, index year, and year of migraine diagnosis. All enrollees received follow-up until the end of 2013 to measure dementia incidence. We identified 1,402 TCM users and non-TCM users after frequency matching. A total of 134 subjects were newly diagnosed with dementia during the follow-up period. TCM users were significantly less likely to develop dementia than non-TCM users. The most frequently prescribed formulae and single Chinese herbal products were Jia-Wei-Xiao-Yao-San and Yan-Hu-Suo, respectively. This population-based study revealed a decreased dementia risk in migraine patients with TCM use. These findings may provide a reference for dementia prevention strategies, and help integrate TCM into clinical intervention programs that provide a favorable prognosis for migraine patients.

Dementia in Women

Despite the progress made in the understanding of the etiology, neuropathophysiology, and treatment of different types of dementia, such disorders continue to pose huge health problems worldwide. The differential effect of the burden of disease on women is just being realized. These effects range from direct effects of the disease processes themselves, the way women experience the disease, and the caregiver burden. This article provides a brief overview of the available information on this topic.

Sex Matters: Hippocampal Volume Predicts Individual Differences in Associative Memory in Cognitively Normal Older Women but Not Men

The hippocampus plays a prominent role in associative memory by supporting relational binding and recollection processes. Structural atrophy in the hippocampus is likely to induce associative memory deficits in older adults. Previous studies have primarily focused on average age-related differences in hippocampal structure and memory performance. To date, however, it remains unclear whether individual differences in hippocampal morphometry underlie differential associative memory performance, and whether there are sex differences in the structural correlates of associative memory in healthy older adults. Here, we used voxel-based morphometry (VBM) to examine the extent to which gray matter volume (GMV) of the hippocampus predicts associative memory performance in cognitively normal older adults. Seventy-one participants completed a cued recall paired-associative learning test (PALT), which consists of novel associations and semantically related associations, and underwent magnetic resonance imaging (MRI). We observed worse associative memory performance and larger variability for novel associations than for semantically related associations. The VBM results revealed that higher scores on associative memory for novel associations were related to greater hippocampal GMV across all older adults. When considering men and women separately, the correlation between hippocampal GMV and associative memory performance for novel associations reached significance only in older women. These findings suggest that hippocampal structural volumes may predict individual differences in novel associative memory in older women but not men.

A quantitative meta-analysis of olfactory dysfunction in mild cognitive impairment

BACKGROUND

The connection between Alzheimer's disease (AD) and olfactory deficits is well documented and further, alterations in olfactory functioning may signal declines in functions associated with dementia. The aim of the present comprehensive meta-analysis was to investigate the nature of olfactory deficits in mild cognitive impairment (MCI).

METHODS

Articles were identified through computerised literature search from inception to 30 June 2016 using PubMed, MEDLINE and PsychInfo databases. In order to control for differences in sample size during effect size computation, studies were weighted according to their inverse variance estimates.

RESULTS

31 articles (62 effects) were identified, which included 1993 MCI patients and 2861 healthy older adults (HOA). Included studies contrasted odour identification, discrimination, detection threshold and/or memory between cases and controls. Moderate to large and heterogeneous effects were seen for olfactory deficits in MCI relative to HOA (d=-0.76, 95% CI -0.87<δ<-0.64). Moderator analysis revealed that tests of odour identification yielded larger effect sizes than those of odour detection threshold or memory. In addition, a potential interaction between age and sex was observed, with male patients carrying a larger burden of olfactory deficit and older female patients performing better on olfactory tests.

CONCLUSIONS AND RELEVANCE

Olfactory deficits are present and robust in MCI. Odour identification is most impaired in MCI, which parallels the most prominent sensory deficit seen in AD. As such, a simple-to-administer test of odour identification warrants inclusion in the screening of individuals at risk for developing AD.

Sex and gender differences in the treatment of Alzheimer's disease: A systematic review of randomized controlled trials

In recent years, epidemiological, clinical, and biological evidence has drawn the attention on the influence of sex and gender on Alzheimer's disease (AD). Nevertheless, not enough attention has been paid to their impact on treatment outcomes. The present study is aimed at systematically retrieve, review and discuss data coming from available randomized placebo-controlled trials (RCTs) on currently marketed treatments for AD (i.e., cholinesterase inhibitors [ChEIs] and memantine) in order to describe possible sex and gender differences in their efficacy, safety and tolerability. A systematic review of literature was performed. None of the retrieved studies reported data on the efficacy, safety and tolerability of considered medications separately in male and female patients with AD. We thus analyzed 48 excluded studies of potential interest, that is, almost all of the currently available trials on the four considered drugs. Nearly all the considered RCTs recruited a larger number of female participants to mirror the sexually unbalanced prevalence of AD. Only two studies took into account the potential influence of sex and gender on treatment efficacy, reporting no significant differences between men and women. None of the studies investigated potential sex and gender differences in the safety and tolerability of the four considered treatments. The existence of sex and gender differences in the efficacy and tolerability of ChEIs and memantine in AD has, to date, drawn limited to no attention. However, a considerable amount of data, with an adequate representativeness in terms of sex/gender distribution, seem to be already available for dedicated analyses on this topic. A greater effort should be made to collect and report data on those factors interacting with sex and gender that may significantly influence clinical manifestations, outcomes, and trajectories over time of AD patients.

Molecular and cellular pathophysiology of preclinical Alzheimer's disease

Although the two pathological hallmarks of Alzheimer's disease (AD), senile plaques composed of amyloid-β (Aβ) peptides and neurofibrillary tangles (NFTs) consisting of hyperphosphorylated tau, have been studied extensively in postmortem AD and relevant animal and cellular models, the pathogenesis of AD remains unknown, particularly in the early stages of the disease where therapies presumably would be most effective. We and others have demonstrated that Aβ plaques and NFTs are present in varying degrees before the onset and throughout the progression of dementia. In this regard, aged people with no cognitive impairment (NCI), mild cognitive impairment (MCI, a presumed prodromal AD transitional state, and AD all present at autopsy with varying levels of pathological hallmarks. Cognitive decline, a requisite for the clinical diagnosis of dementia associated with AD, generally correlates better with NFTs than Aβ plaques. However, correlations are even higher between cognitive decline and synaptic loss. In this review, we illustrate relevant clinical pathological research in preclinical AD and throughout the progression of dementia in several areas including Aβ and tau pathobiology, single population expression profiling of vulnerable hippocampal and basal forebrain neurons, neuroplasticity, neuroimaging, cerebrospinal fluid (CSF) biomarker studies and their correlation with antemortem cognitive endpoints. In each of these areas, we provide evidence for the importance of studying the pathological hallmarks of AD not in isolation, but rather in conjunction with other molecular, cellular, and imaging markers to provide a more systematic and comprehensive assessment of the multiple changes that occur during the transition from NCI to MCI to frank AD.