Women are disproportionately affected by Alzheimer’s disease (AD) in terms of both disease prevalence and severity. Previous autopsy work has suggested that, in the presence of AD neuropathology, females are more susceptible to the clinical manifestation of AD. This manuscript extends that work by evaluating whether sex alters the established associations between cerebrospinal fluid (CSF) biomarker levels and brain aging outcomes (hippocampal volume, cognition). Participants were drawn from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) and included individuals with normal cognition (n=348), mild cognitive impairment (n=565), and AD (n=185). We leveraged mixed effects regression models to assess the interaction between sex and baseline cerebrospinal fluid biomarker levels of amyloid-β42 (Aβ-42) and total tau on cross-sectional and longitudinal brain aging outcomes. We found a significant interaction between sex and Aβ-42 on longitudinal hippocampal atrophy (p=0.002), and longitudinal decline in memory (p=0.017) and executive function (p=0.025). Similarly, we observed an interaction between sex and total tau level on longitudinal hippocampal atrophy (p=0.008), and longitudinal decline in executive function (p=0.034). Women with Aβ-42 and total tau levels indicative of worse pathological changes showed more rapid hippocampal atrophy and cognitive decline. The sex difference was particularly pronounced among individuals with MCI, with lower education, and varied by APOE ε4 allele. These results suggest females may be more susceptible to the clinical manifestation of AD.
BackgroundIndividuals with Down Syndrome (DS) are reported to experience early onset of brain aging. However, it is not well understood how pre-existing neurodevelopmental effects versus neurodegenerative processes might be contributing to the observed pattern of brain atrophy in younger adults with DS. The aims of the current study were to: (1) to confirm previous findings of age-related changes in DS compared to adults with typical development (TD), (2) to test for an effect of these age-related changes in a second neurodevelopmental disorder, Williams syndrome (WS), and (3) to identify a pattern of regional age-related effects that are unique to DS.MethodsHigh-resolution T1-weighted MRI of the brains of subjects with DS, WS, and TD controls were segmented, and estimates of regional brain volume were derived using FreeSurfer. A general linear model was employed to test for age-related effects on volume between groups. Secondary analyses in the DS group explored the relationship between brain volume and neuropsychological tests and APOE.ResultsConsistent with previous findings, the DS group showed significantly greater age-related effects relative to TD controls in total gray matter and in regions of the orbitofrontal cortex and the parietal cortex. Individuals with DS also showed significantly greater age-related effects on volume of the left and right inferior lateral ventricles (LILV and RILV, respectively). There were no significant differences in age-related effects on volume when comparing the WS and TD groups. In the DS group, cognitive tests scores measuring signs of dementia and APOE ϵ4 carrier status were associated with LILV and RILV volume.ConclusionsIndividuals with DS demonstrated a unique pattern of age-related effects on gray matter and ventricular volume, the latter of which was associated with dementia rating scores in the DS group. Results may indicate that early onset of brain aging in DS is primarily due to DS-specific neurodegenerative processes, as opposed to general atypical neurodevelopment.
Summary Variations in the KCNJ6 gene appear to influence both acute and chronic pain phenotypes. G-protein coupled inwardly rectifying potassium (GIRK) channels are effectors determining degree of analgesia experienced upon opioid receptor activation by endogenous and exogenous opioids. The impact of GIRK-related genetic variation on human pain responses has received little research attention. We used a tag SNP approach to comprehensively examine pain-related effects of KCNJ3 (GIRK1) and KCNJ6 (GIRK2) gene variation. Forty-one KCNJ3 and 69 KCNJ6 tag SNPs were selected, capturing the known variability in each gene. The primary sample included 311 Caucasian patients undergoing total knee arthroplasty in whom post-surgical oral opioid analgesic medication order data were available. Primary sample findings were then replicated in an independent Caucasian sample of 63 healthy pain-free individuals and 75 individuals with chronic low back pain (CLBP) who provided data regarding laboratory acute pain responsiveness (ischemic task) and chronic pain intensity and unpleasantness (CLBP Only). Univariate quantitative trait analyses in the primary sample revealed that 8 KCNJ6 SNPs were significantly associated with the medication order phenotype (p < 0.05); overall effects of the KCNJ6 gene (gene set-based analysis) just failed to reach significance (p=.054). No significant KCNJ3 effects were observed. A continuous GIRK Related Risk Score (GRRS) was derived in the primary sample to summarize each individual's number of KCNJ6 “pain risk” alleles. This GRRS was applied to the replication sample, which revealed significant associations (p<.05) between higher GRRS values and lower acute pain tolerance and higher CLBP intensity and unpleasantness. Results suggest further exploration of the impact of KCNJ6 genetic variation on pain outcomes is warranted.
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