Sex-Related Reserve Hypothesis in Alzheimer's Disease: Changes in Cortical Thickness with a Five-Year Longitudinal Follow-Up

Confronting Alzheimer's Disease Risk in Women: A Feasibility Study of Memory Screening as Part of the Annual Gynecological Well-Woman Visit

Objective: Routine health care visits offer the opportunity to screen older adults for symptoms of Alzheimer's disease (AD). Many women see their gynecologist as their primary health care provider. Given this unique relationship, the Women's Preventive Services Initiative and the American College of Obstetrics and Gynecology advocate for integrated care of women at all ages. It is well-established that women are at increased risk for AD, and memory screening of older women should be paramount in this effort. Research is needed to determine the feasibility and value of memory screening among older women at the well-woman visit. Materials and Methods: Women aged 60 and above completed a 5-item subjective memory screener at their well-woman visit at the Columbia University Integrated Women's Health Program. Women who endorsed any item were considered to have a positive screen and were given the option to pursue clinical evaluation. Rates of positive screens, item endorsement, and referral preferences were examined. Results: Of the 530 women approached, 521 agreed to complete the screener. Of those, 17.5% (n = 91) were classified as positive. The most frequently endorsed item was difficulty with memory or thinking compared with others the same age. Among women with positive screens, 57.5% were interested in pursuing clinical referrals to a memory specialist. Conclusion: Results support the feasibility and potential value of including subjective memory screening as part of a comprehensive well-woman program. Early identification of memory loss will enable investigation into the cause of memory symptoms and longitudinal monitoring of cognitive change.

Sex and gender differences in Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis: a narrative review

Neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), exhibit high phenotypic variability and they are very common in the general population. These diseases are associated with poor prognosis and a significant burden on patients and their caregivers. Although increasing evidence suggests that biological sex is an important factor for the development and phenotypical expression of some NDs, the role of sex and gender in the diagnosis and prognosis of NDs has been poorly explored. Current knowledge relating to sex- and gender-related differences in the epidemiology, clinical features, biomarkers, and treatment of AD, PD, and ALS will be summarized in this narrative review. The cumulative evidence hitherto collected suggests that sex and gender are factors to be considered in explaining the heterogeneity of these NDs. Clarifying the role of sex and gender in AD, PD, and ALS is a key topic in precision medicine, which will facilitate sex-specific prevention and treatment strategies to be implemented in the near future.

Sex differences in early-onset Alzheimer's disease

INTRODUCTION

Sex is believed to drive heterogeneity in Alzheimer's disease (AD), although evidence in early-onset AD (<65 years, EOAD) is scarce.

METHODS

We included 62 EOAD patients and 44 healthy controls (HC) with cerebrospinal fluid (CSF) AD's core biomarkers and neurofilament light chain levels, neuropsychological assessment, and 3T-MRI. We measured cortical thickness (CTh) and hippocampal subfield volumes (HpS) using Freesurfer. Adjusted linear models were used to analyze sex-differences and the relationship between atrophy and cognition.

RESULTS

Compared to same-sex HC, female-EOAD showed greater cognitive impairment and broader atrophy burden than male-EOAD. In a direct female-EOAD and male-EOAD comparison, there were slight differences in temporal CTh, with no differences in cognition or HpS. CSF tau levels were higher in female-EOAD than in male-EOAD. Greater atrophy was associated with worse cognition in female-EOAD.

CONCLUSIONS

At diagnosis, there are sex-differences in the pattern of cognitive impairment, atrophy burden and CSF tau in EOAD, suggesting there is an influence of sex on pathology spreading and susceptibility to the disease in EOAD.

Sex is a defining feature of neuroimaging phenotypes in major brain disorders

Sex is a biological variable that contributes to individual variability in brain structure and behavior. Neuroimaging studies of population-based samples have identified normative differences in brain structure between males and females, many of which are exacerbated in psychiatric and neurological conditions. Still, sex differences in MRI outcomes are understudied, particularly in clinical samples with known sex differences in disease risk, prevalence, and expression of clinical symptoms. Here we review the existing literature on sex differences in adult brain structure in normative samples and in 14 distinct psychiatric and neurological disorders. We discuss commonalities and sources of variance in study designs, analysis procedures, disease subtype effects, and the impact of these factors on MRI interpretation. Lastly, we identify key problems in the neuroimaging literature on sex differences and offer potential recommendations to address current barriers and optimize rigor and reproducibility. In particular, we emphasize the importance of large-scale neuroimaging initiatives such as the Enhancing NeuroImaging Genetics through Meta-Analyses consortium, the UK Biobank, Human Connectome Project, and others to provide unprecedented power to evaluate sex-specific phenotypes in major brain diseases.

Multimodal neuroimaging of sex differences in cognitively impaired patients on the Alzheimer's continuum: greater tau-PET retention in females

We assessed sex differences in amyloid- and tau-PET retention in 119 amyloid positive patients with mild cognitive impairment or Alzheimer's disease (AD) dementia. Patients underwent 3T-MRI, ¹¹C-PIB amyloid-PET and ¹⁸F-Flortaucipir tau-PET. Linear ordinary least squares regression models tested sex differences in Flortaucipir-PET SUVR in a summary temporal region of interest as well as global PIB-PET. No sex differences were observed in demographics, Clinical Dementia Rating Sum of Boxes (CDR-SoB), Mini-Mental State Exam (MMSE), raw episodic memory scores, or cortical thickness. Females had higher global PIB SUVR (η_p²=.043, p=.025) and temporal Flortaucipir SUVR (η_p²=.070, p=.004), adjusting for age and CDR-SoB. Sex differences in temporal Flortaucipir-PET remained significant when controlling additionally for PIB SUVR and APOE4 status (η_p²=.055, p=.013), or when using partial volume-corrected data. No sex differences were present in areas of known Flortaucipir off-target binding. Overall, females demonstrated greater AD regional tau-PET burden than males despite clinical comparability. Further characterization of sex differences will provide insight into AD pathogenesis and support development of personalized therapeutic strategies.

Older age and male sex are associated with higher cerebrovascular impedance

Cerebral blood flow (CBF) becomes pulsatile in response to the pulsatile change in perfusion pressure that is regulated by cerebrovascular impedance. In this study, we aimed to characterize age-related differences in cerebrovascular impedance across the adult lifespan. Carotid artery pressure [(CAP), via applanation tonometry] and CBF velocity (CBFV) in the middle cerebral artery (via transcranial Doppler) were measured in 148 healthy adults (21-79 yr, 62% women). Cerebrovascular impedance was quantified using transfer function analysis. Coherence between changes in CBFV and CAP was >0.90 in the frequency range of 0.78-2.73 Hz, suggesting a linear dynamic relationship between these two variables. Impedance modulus at the first harmonics (0.78-1.56 Hz) of CBFV and CAP oscillations (Z₁), reflecting mainly heart rate frequency, was 20% higher in the old (>64 yr, P = 0.002) and 13% higher in the middle-aged (45-64 yr, P = 0.08) than in young individuals (<45 yr). In addition, Z₁ was 24% higher in men than in women (P < 0.001). Multiple linear regression analysis revealed that Z₁ is negatively associated with systolic (β = -0.470), diastolic (β = -0.418), pulsatile (β = -0.374), and mean CBFV (β = -0.473; P < 0.001 for all) after adjustment for age, sex, and body mass index (BMI). These results suggest that older age and male sex are associated with higher cerebrovascular impedance than young individuals, which may contribute to brain hypoperfusion.NEW & NOTEWORTHY Impedance modulus at the first harmonics of cerebral blood flow velocity (CBFV) and carotid artery pressure oscillations (Z₁) was higher in the old (>64 yr) than in the young individuals (<45 yr), and it was higher in men than in women. Z₁ is negatively associated with CBFV after adjustment for age, sex, and body mass index. Increases in cerebrovascular impedance with age may buffer systemic arterial pressure fluctuations at the cost of increased brain hypoperfusion risk.

Medical Symptom Validity Test (MSVT) profiles in individuals being evaluated for Alzheimer's disease

OBJECTIVE

Our purpose was to determine whether Medical Symptom Validity Test (MSVT) profiles could differentiate performance invalidity from true impairment in patients with varying levels of memory impairment and functional ability being evaluated for Alzheimer's disease (AD). Method: Seventy-three older adults (13 healthy controls, 25 mild cognitive impairment [MCI], 16 mild AD, 19 moderate AD) were evaluated with a neuropsychological battery including the MSVT and activities of daily living (ADL) measures. Using MSVT classification guidelines, examinees' MSVT profiles were categorized as: 1) valid, 2) invalid, 3) weak memory, or 4) genuine memory impairment (GMIP). Results: Eighty-four percent of moderate AD examinees produced a GMIP. Among MCI and mild AD examinees, who had only modestly affected ADLs, a substantial proportion manifested a GMIP (40% and 62.5%, respectively). An invalid profile was uncommon across patient groups (12.5% in mild AD, 5.3% in moderate AD, and 0% in MCI). Conclusions: The MSVT functions reasonably well in a dementia sample to determine if an examinee has an invalid profile, although for mild AD examinees, the false positive rate is slightly above the recommended 10% cut-off. However, even individuals with MCI, mild AD and relative preservation of ADLs may manifest a GMIP, demonstrating that such profile is found across patients with lower and higher degrees of functional impairment. Given this finding, the usefulness of the GMIP in differentiating performance invalidity from true impairment in patients being evaluated for AD appears limited.