Aging brain最新文献

The ability to sleep declines with age. The National Sleep Foundation, USA has recommended a minimum sleep amount for all ages. Individuals who experience sleep lesser than the recommended amount could be sleep-deprived. Several factors like stress, altered circadian cycle, medical conditions, etc. cause sleep deficiency. Almost 50–60 % of elderly population suffer from sleep disorders such as sleep apnea, restless legs syndrome, REM sleep behavior disorder, etc. Chronic sleep deprivation may further lead to the development of diseases such as Alzheimer's and Parkinson's. This paper reviews the prevalence of sleep disorders and consequences of sleep loss in young and old adults.

This systematic review examined the longitudinal association between amyloid-β (Aβ) accumulation and cognitive decline in cognitively healthy adults. It was conducted using the PubMed, Embase, PsycInfo, and Web of Science databases. The methodological quality of the selected articles was assessed. In fine, seventeen longitudinal clinical studies were included in this review. A minority (seven out of 17) of studies reported a statistically significant association or prediction of cognitive decline with Aβ change, measured by positron emission tomography (PET; n = 6) and lumbar puncture (n = 1), with a mean follow-up duration of 3.17 years for cognition and 2.99 years for Aβ. The studies reporting significant results with PET found differences in the frontal, posterior cingular, lateral parietal and global (whole brain) cortices as well as in the precuneus. Significant associations were found with episodic memory (n = 6) and global cognition (n = 1). Five of the seven studies using a composite cognitive score found significant results. A quality assessment revealed widespread methodological biases, such as failure to report or account for loss-to follow up and missing data, and failure to report p-values and effect sizes of non-significant results. Overall, the longitudinal association between Aβ accumulation and cognitive decline in preclinical Alzheimer’s disease remains unclear. The discrepancy in results between studies may be explained in part by the choice of neuroimaging technique used to measure Aβ change, the duration of longitudinal studies, the heterogeneity of the healthy preclinical population, and importantly, the use of a composite score to capture cognitive changes with increased sensitivity. More longitudinal studies with larger sample sizes are needed to elucidate this relationship.

Age-related changes in cortical volumes are well established but relatively few studies probed its constituents, surface area (SA) and thickness (TH). Here we analyzed 10-year, 3-waves longitudinal data from a large sample of healthy individuals (baseline age = 55–80). The findings showed marked age-related changes of SA in frontal, temporal, and parietal association cortices, and Bivariate Latent Change Score models revealed significant SA-associations with changes in speed of processing in both the 5- and 10-year models. The corresponding results for TH revealed a late onset of thinning and significant associations with reduced cognition in the 10-year model only. Taken together, our findings suggest that cortical surface area shrinks and impacts information-processing capacity gradually in aging, whereas cortical thinning only manifests and impacts fluid cognition in advanced aging.

The precision of temporal multisensory integration is associated with specific aspects of physical functioning in ageing, including gait speed and incidents of falling. However, it is unknown if such an association exists between multisensory integration and grip strength, an important index of frailty and brain health and predictor of disease and mortality in older adults. Here, we investigated whether temporal multisensory integration is associated with longitudinal (eight-year) grip strength trajectories in a large sample of 2,061 older adults (mean age = 64.42 years, SD = 7.20; 52% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). Grip strength (kg) for the dominant hand was assessed with a hand-held dynamometer across four testing waves. Longitudinal k-means clustering was applied to these data separately for sex (male, female) and age group (50–64, 65–74, 75+ years). At wave 3, older adults participated in the Sound Induced Flash Illusion (SIFI), a measure of the precision of temporal audio-visual integration, which included three audio-visual stimulus onset asynchronies (SOAs): 70, 150 and 230 ms. Results showed that older adults with a relatively lower (i.e., weaker) grip strength were more susceptible to the SIFI at the longer SOAs compared to those with a relatively higher (i.e., stronger) grip strength (p <.001). These novel findings suggest that older adults with relatively weaker grip strength exhibit an expanded temporal binding window for audio-visual events, possibly reflecting a reduction in the integrity of the central nervous system.

Working Memory (WM) training has shown promise in supporting cognitive functioning in older adult populations, but effects that generalize beyond the trained task have been inconsistent. Targeting cognitive processes in isolation might be a limiting factor given that metacognitive and motivational factors have been shown to impact older adults’ engagement with challenging cognitive activities, such as WM training. The current feasibility study implemented a novel metacognitive intervention in conjunction with WM training in older adults and examined its potential amplifying short- and long-term effects on cognitive and self-report outcomes as compared to WM or active control training alone. One-hundred and nineteen older adults completed a cognitive training over the course of 20 sessions at home. The cognitive training targeted either WM or general knowledge. In addition, one of the WM training groups completed a metacognitive program via group seminars. We tested for group differences in WM, inhibitory control, and episodic memory, and we assessed participants’ perceived self-efficacy and everyday memory failures. At post-test, we replicated earlier work by demonstrating that participants who completed the WM intervention outperformed the active control group in non-trained WM measures, and to some extent, in inhibitory control. However, we found no evidence that the supplemental metacognitive program led to benefits over and above the WM intervention. Nonetheless, we conclude that our metacognitive program is a step in the right direction given the tentative long-term effects and participants’ positive feedback, but more longitudinal data with larger sample sizes are needed to confirm these early findings.

Past research has shown that as individuals age, there are decreases in within-network connectivity and increases in between-network connectivity, a pattern known as functional dedifferentiation. While the mechanisms behind reduced network segregation are not fully understood, evidence suggests that age-related differences in the dopamine (DA) system may play a key role. The DA D1-receptor (D1DR) is the most abundant and age-sensitive receptor subtype in the dopaminergic system, known to modulate synaptic activity and enhance the specificity of the neuronal signals. In this study from the DyNAMiC project (N = 180, 20-79y), we set out to investigate the interplay among age, functional connectivity, and dopamine D1DR availability. Using a novel application of multivariate Partial Least squares (PLS), we found that older age, and lower D1DR availability, were simultaneously associated with a pattern of decreased within-network and increased between-network connectivity. Individuals who expressed greater distinctiveness of large-scale networks exhibited more efficient working memory. In line with the maintenance hypotheses, we found that older individuals with greater D1DR in caudate exhibited less dedifferentiation of the connectome, and greater working memory, compared to their age-matched counterparts with less D1DR. These findings suggest that dopaminergic neurotransmission plays an important role in functional dedifferentiation in aging with consequences for working memory function at older age.