Sex-related differences in whole brain volumes at age 70 in association with hyperglycemia during adult life

Sex differences between mid-life glycaemic traits and brain volume at age 70: a population-based study

Higher HbA1c in mid-to-later life has been associated with smaller whole brain volume (WBV) in older women but not men. We explored whether this association was replicated using different markers of (i) glycaemic health [fasting glucose, insulin resistance (HOMA2-IR), and β-cell function (HOMA-%B)] and (ii) brain structure (white or grey matter volume). 453 participants (51% men) from the 1946 British Birth Cohort had glycaemic measures (at age 60-64) and MRI measures (at age ∼70). In women, higher fasting glucose and insulin resistance at age ∼60 were weakly associated with lower WBV at age ∼70 [eg, fasting glucose: β* = -0.07 (95% CI: -0.13, -0.01), P = .02]. No associations emerged for men for any glycaemic marker. HOMA-%B was not associated with brain outcomes in either sex. Women's later-life brain health may be more vulnerable to midlife hyperglycaemia.

Effects of glycaemic control on memory performance, hippocampal volumes and depressive symptomology

BACKGROUND

Diabetes and poor glycaemic control have been shown to negatively impact cognitive abilities, while also raising risk of both mood disorders and brain structural atrophy. Sites of atrophy include the hippocampus, which has been implicated in both memory performance and depression. The current study set out to better characterise the associations between poor glycaemic control, memory performance, and depression symptoms, and investigate whether loss of hippocampal volume could represent a neuropathological mechanism underlying these.

METHODS

1331 participants (60.9% female, age range 18-88 (Mean = 44.02), 6.5% with likely diabetes) provided HbA1c data (as an index of glycaemic control), completed a word list learning task, and a validated depression scale. A subsample of 392 participants underwent structural MRI; hippocampal volumes were extracted using FreeSurfer.

RESULTS

Partial correlation analyses (controlling for age, gender, and education) showed that, in the full sample, poorer glycaemic control was related to lower word list memory performance. In the MRI sub-sample, poorer glycaemic control was related to higher depressive symptoms, and lower hippocampal volumes. Total hippocampus volume partially mediated the association between HbA1c levels and depressive symptoms.

CONCLUSIONS

Results emphasise the impact of glycaemic control on memory, depression and hippocampal volume and suggest hippocampal volume loss could be a pathophysiological mechanism underlying the link between HbA1c and depression risk; inflammatory and stress-hormone related processes might have a role in this.

Is the change in longitudinal cognitive function in older adults with diabetes affected by trajectory classes of depressive symptoms?

OBJECTIVE

This study aims to identify classes based on the trajectory of depressive symptoms and to examine the impact of trajectory classes of depressive symptoms on longitudinal changes in cognitive function in older adults with diabetes.

METHODS

This is a secondary data analysis of 572 older adults with diabetes using data from the 5th (2014) to 8th (2020) wave of the Korean longitudinal study of aging. Analysis of latent class growth and the effect of trajectories of depressive symptoms on cognitive function was examined using a latent growth curve model. This analysis has been found to be functional in change trajectories and in describing the direction of the trajectory.

RESULTS

The trajectory of depressive symptoms was classified into four classes: low-stable (36.89%), high-decreasing (20.28%), low-increasing (18.71%), and high-persistent (24.13%). Compared with the high-persistent class, higher initial levels of cognitive function were observed in the high-decreasing and low-stable classes. Compared with the high-persistent class, a slower rate of cognitive decline was observed in the low-stable class (B = 0.410, p = .021).

CONCLUSIONS

Continuous monitoring of depressive symptoms and early management of depressive symptoms for community-dwelling older adults with diabetes can help prevent the cognitive decline and delay the deterioration of cognitive function.

Sex and gender differences in cognitive resilience to aging and Alzheimer's disease

Sex and gender-biological and social constructs-significantly impact the prevalence of protective and risk factors, influencing the burden of Alzheimer's disease (AD; amyloid beta and tau) and other pathologies (e.g., cerebrovascular disease) which ultimately shape cognitive trajectories. Understanding the interplay of these factors is central to understanding resilience and resistance mechanisms explaining maintained cognitive function and reduced pathology accumulation in aging and AD. In this narrative review, the ADDRESS! Special Interest Group (Alzheimer's Association) adopted a multidisciplinary approach to provide the foundations and recommendations for future research into sex- and gender-specific drivers of resilience, including a sex/gender-oriented review of risk factors, genetics, AD and non-AD pathologies, brain structure and function, and animal research. We urge the field to adopt a sex/gender-aware approach to resilience to advance our understanding of the intricate interplay of biological and social determinants and consider sex/gender-specific resilience throughout disease stages. HIGHLIGHTS: Sex differences in resilience to cognitive decline vary by age and cognitive status. Initial evidence supports sex-specific distinctions in brain pathology. Findings suggest sex differences in the impact of pathology on cognition. There is a sex-specific change in resilience in the transition to clinical stages. Gender and sex factors warrant study: modifiable, immune, inflammatory, and vascular.

Sex Differences in the Effect of Diabetes on Cerebral Glucose Metabolism

The neuroimaging literature indicates that brain structure and function both deteriorate with diabetes, but information on sexual dimorphism in diabetes-related brain alterations is limited. This study aimed to ascertain whether brain metabolism is influenced by sex in an animal model of diabetes. Eleven rats (male, n = 5; female, n = 6) received a single intraperitoneal injection of 70 mg/kg streptozotocin (STZ) to develop diabetes. Another 11 rats (male, n = 5; female, n = 6) received the same amount of solvent through a single intraperitoneal injection. Longitudinal positron emission tomography scans were used to assess cerebral glucose metabolism before and 4 weeks after STZ or solvent administration. Before STZ or solvent injections, there was no evidence of sexual dimorphism in cerebral metabolism (p > 0.05). Compared with healthy control animals, rats with diabetes had significantly decreased brain metabolism in all brain regions (all p < 0.05). In addition, female diabetic rats exhibited further reduction in cerebral metabolism, relative to male diabetic rats (p < 0.05). The results of this study may provide some biological evidence, supporting the existence of a sexual dimorphism in diabetes-related complications.