Insomnia Moderates the Relationship Between Amyloid-β and Cognitive Decline in Late-Life Adults without Dementia

The association between insomnia and cognitive decline: A scoping review

OBJECTIVE

This study aimed to investigate the association between insomnia and cognitive decline to provide insights for clinical interventions and future research.

METHODS

The PubMed, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases were systematically searched to identify studies on the association between insomnia and cognitive decline published within the last decade. The quality of the included studies was evaluated, followed by data extraction and summary analysis.

RESULTS

A total of 36 studies were included in the review. Both subjective and objective measures were utilized across 12 indices to assess sleep status, while cognitive function was evaluated using 5 scales and 34 tests. The results revealed a significantly increased risk of cognitive decline or Alzheimer's disease among patients with insomnia, alongside notable impairments in attention, memory, visuospatial abilities, executive function, and verbal memory. Comprehensive assessments of cognitive domains were more sensitive in detecting group differences compared to assessments of specific cognitive sub-functions. Furthermore, MRI analyses showed reduced gray matter volumes in regions such as the prefrontal cortex, cingulate gyrus, temporal lobe, and hippocampus, together with reduced integrity of the white matter in patients with insomnia.

CONCLUSIONS

The findings indicate a potentially bidirectional relationship between insomnia and cognitive decline, suggesting that each may influence and exacerbate the other. Insomnia may increase the risk of cognitive decline and appears to be associated with reduced gray matter volume and compromised white matter integrity in the brain, which could potentially lead to declines in attention, memory, visuospatial abilities, executive function, and verbal memory. Conversely, cognitive decline may contribute to the onset of insomnia, further deteriorating sleep quality. However, further research is necessary to fully comprehend this intricate relationship.

Interactions between mild depressive symptoms and amyloid pathology on the trajectory of neurodegeneration, cognitive decline, and risk of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) was driven by the interplay between modifiable environmental factors and β-amyloid (Aβ) pathology. We aimed to investigate the interaction effects of mild depressive symptoms (MDS) with Aβ on AD development.

METHODS

Longitudinal data of 1746 non-demented adults (mean age = 73 years, female = 53 %, maximum = 10 years) were derived from the Alzheimer's Disease Neuroimaging Initiative cohort. MDS was separately defined by the baseline status, longitudinal latent class, and average intensity during follow-up. Amyloid-positive (A+) status was determined based on cerebrospinal fluid levels of β-amyloid. Regression models were employed to analyze the interactive effects of MDS with A+ on cognitive decline, neurodegeneration, and AD incidence.

RESULTS

Individuals with both A+ status and MDS at baseline experienced the fastest neurodegeneration (p < 0.01), cognitive decline (p < 0.05), and a higher risk of developing AD (HR = 5.23, p < 0.001). Furthermore, A+ participants with the trajectory of increasing depressive symptoms demonstrated more pronounced neurodegeneration (p < 0.001), cognitive decline (p < 0.01), and elevated risk of AD (HR = 10.45, p < 0.001). Finally, A+ status in combination with a higher average intensity of depressive symptoms was associated with faster brain atrophy (p < 0.01) and brain metabolism decline (p < 0.05), cognitive decline (p < 0.05), and higher AD risk (HR = 13.99, p < 0.001).

CONCLUSION

These findings emphasized that the MDS-Aβ interaction relationship should be considered in risk stratification, prediction, and early management of neurodegeneration and cognitive decline in the pre-dementia stage.

How Do Modifiable Risk Factors Affect Alzheimer's Disease Pathology or Mitigate Its Effect on Clinical Symptom Expression?

Epidemiological studies show that modifiable risk factors account for approximately 40% of the population variability in risk of developing dementia, including sporadic Alzheimer's disease (AD). Recent findings suggest that these factors may also modify disease trajectories of people with autosomal-dominant AD. With positron emission tomography imaging, it is now possible to study the disease many years before its clinical onset. Such studies can provide key knowledge regarding pathways for either the prevention of pathology or the postponement of its clinical expression. The former "resistance pathway" suggests that modifiable risk factors could affect amyloid and tau burden decades before the appearance of cognitive impairment. Alternatively, the resilience pathway suggests that modifiable risk factors may mitigate the symptomatic expression of AD pathology on cognition. These pathways are not mutually exclusive and may appear at different disease stages. Here, in a narrative review, we present neuroimaging evidence that supports both pathways in sporadic AD and autosomal-dominant AD. We then propose mechanisms for their protective effect. Among possible mechanisms, we examine neural and vascular mechanisms for the resistance pathway. We also describe brain maintenance and functional compensation as bases for the resilience pathway. Improved mechanistic understanding of both pathways may suggest new interventions.

The Alzheimer's Disease Neuroimaging Initiative in the era of Alzheimer's disease treatment: A review of ADNI studies from 2021 to 2022

The Alzheimer's Disease Neuroimaging Initiative (ADNI) aims to improve Alzheimer's disease (AD) clinical trials. Since 2006, ADNI has shared clinical, neuroimaging, and cognitive data, and biofluid samples. We used conventional search methods to identify 1459 publications from 2021 to 2022 using ADNI data/samples and reviewed 291 impactful studies. This review details how ADNI studies improved disease progression understanding and clinical trial efficiency. Advances in subject selection, detection of treatment effects, harmonization, and modeling improved clinical trials and plasma biomarkers like phosphorylated tau showed promise for clinical use. Biomarkers of amyloid beta, tau, neurodegeneration, inflammation, and others were prognostic with individualized prediction algorithms available online. Studies supported the amyloid cascade, emphasized the importance of neuroinflammation, and detailed widespread heterogeneity in disease, linked to genetic and vascular risk, co-pathologies, sex, and resilience. Biological subtypes were consistently observed. Generalizability of ADNI results is limited by lack of cohort diversity, an issue ADNI-4 aims to address by enrolling a diverse cohort.

Thwarting Alzheimer's Disease through Healthy Lifestyle Habits: Hope for the Future

Alzheimer's disease (AD) is a neurodegenerative disorder that slowly disintegrates memory and thinking skills. Age is known to be the major risk factor in AD, but there are several nonmodifiable and modifiable causes. The nonmodifiable risk factors such as family history, high cholesterol, head injuries, gender, pollution, and genetic aberrations are reported to expediate disease progression. The modifiable risk factors of AD that may help prevent or delay the onset of AD in liable people, which this review focuses on, includes lifestyle, diet, substance use, lack of physical and mental activity, social life, sleep, among other causes. We also discuss how mitigating underlying conditions such as hearing loss and cardiovascular complications could be beneficial in preventing cognitive decline. As the current medications can only treat the manifestations of AD and not the underlying process, healthy lifestyle choices associated with modifiable factors is the best alternative strategy to combat the disease.

Sleep and Cognition: A Narrative Review Focused on Older Adults

Little is known regarding sleep's association with the traditional developmental course of late-life cognitive functioning. As the number of older adults increases worldwide, an enhanced understanding of age-related changes in sleep and cognition is necessary to slow decline and promote optimal aging. This review synthesizes the extant literature on sleep and cognitive function in healthy older adults, older adults with insomnia, and older adults with sleep apnea, incorporating information on the potential promising effects of treating poor sleep on cognitive outcomes in older adults. Unifying theories of the sleep-cognition association, possible mechanisms of action, and important unanswered questions are identified.