Three midlife strategies to prevent cognitive impairment due to Alzheimer's disease

Interplay between microglia and environmental risk factors in Alzheimer's disease

Alzheimer's disease, among the most common neurodegenerative disorders, is characterized by progressive cognitive impairment. At present, the Alzheimer's disease main risk remains genetic risks, but major environmental factors are increasingly shown to impact Alzheimer's disease development and progression. Microglia, the most important brain immune cells, play a central role in Alzheimer's disease pathogenesis and are considered environmental and lifestyle "sensors." Factors like environmental pollution and modern lifestyles (e.g., chronic stress, poor dietary habits, sleep, and circadian rhythm disorders) can cause neuroinflammatory responses that lead to cognitive impairment via microglial functioning and phenotypic regulation. However, the specific mechanisms underlying interactions among these factors and microglia in Alzheimer's disease are unclear. Herein, we: discuss the biological effects of air pollution, chronic stress, gut microbiota, sleep patterns, physical exercise, cigarette smoking, and caffeine consumption on microglia; consider how unhealthy lifestyle factors influence individual susceptibility to Alzheimer's disease; and present the neuroprotective effects of a healthy lifestyle. Toward intervening and controlling these environmental risk factors at an early Alzheimer's disease stage, understanding the role of microglia in Alzheimer's disease development, and targeting strategies to target microglia, could be essential to future Alzheimer's disease treatments.

Do Not Worry That Generative AI May Compromise Human Creativity or Intelligence in the Future: It Already Has

Technology alters both perceptions of human intelligence and creativity and the actual processes of intelligence and creativity. Skills that were once important for human intelligence, for example, computational ones, no longer hold anywhere near the same importance they did before the age of computers. The advantage of computers is that they may lead us to focus on what we believe to be more important things than what they have replaced. In the case of penmanship, spelling, or arithmetic computation, such an argument could bear fruit. But in the case of human creativity, the loss of creative skills and attitudes may be a long-term loss to humanity. Generative AI is replicative. It can recombine and re-sort ideas, but it is not clear that it will generate the kinds of paradigm-breaking ideas the world needs right now to solve the serious problems that confront it, such as global climate change, pollution, violence, increasing income disparities, and creeping autocracy.

Skeletal muscle adiposity is a novel risk factor for poor cognition in African Caribbean women

OBJECTIVE

Skeletal muscle adiposity (myosteatosis) is recognized as a major risk factor for cardiometabolic diseases, and it increases with aging. The relationship of myosteatosis with cognitive impairment is unknown.

METHODS

The association of calf myosteatosis (measured by computed tomography-derived skeletal muscle density; higher values indicate less myosteatosis) with cognitive function was examined among 626 African Caribbean women who were aged 40 to 84 years, a population highly vulnerable to increased myosteatosis. Cognition was assessed by the Digit Symbol Substitution Test (DSST), a test of information processing speed (higher scores indicate better performance). Linear regression was used to assess the association of muscle density with DSST.

RESULTS

Adjusting for age, education, muscle area, BMI, hypertension, diabetes, cardiovascular event history, lifestyle factors, lipid-lowering medication use, and menopausal status, a one-SD lower muscle density was associated with a 1.69-point lower DSST score (p = 0.002). BMI, diabetes, and hypertension interactions were not statistically significant, suggesting that the main association was not moderated by overall obesity or cardiometabolic diseases.

CONCLUSIONS

These findings suggest that greater myosteatosis is associated with slower information processing speed, an early indicator of cognitive impairment. Further studies are needed to establish this association in this and other populations using an expanded battery of cognitive tests with longitudinal follow-up and to identify the biological mechanisms underlying this relationship.

Malignant Brain Aging: The Formidable Link Between Dysregulated Signaling Through Mechanistic Target of Rapamycin Pathways and Alzheimer's Disease (Type 3 Diabetes)

Malignant brain aging corresponds to accelerated age-related declines in brain functions eventually derailing the self-sustaining forces that govern independent vitality. Malignant brain aging establishes the path toward dementing neurodegeneration, including Alzheimer's disease (AD). The full spectrum of AD includes progressive dysfunction of neurons, oligodendrocytes, astrocytes, microglia, and the microvascular systems, and is mechanistically driven by insulin and insulin-like growth factor (IGF) deficiencies and resistances with accompanying deficits in energy balance, increased cellular stress, inflammation, and impaired perfusion, mimicking the core features of diabetes mellitus. The underlying pathophysiological derangements result in mitochondrial dysfunction, abnormal protein aggregation, increased oxidative and endoplasmic reticulum stress, aberrant autophagy, and abnormal post-translational modification of proteins, all of which are signature features of both AD and dysregulated insulin/IGF-1-mechanistic target of rapamycin (mTOR) signaling. This article connects the dots from benign to malignant aging to neurodegeneration by reviewing the salient pathologies associated with initially adaptive and later dysfunctional mTOR signaling in the brain. Effective therapeutic and preventive measures must be two-pronged and designed to 1) address complex and shifting impairments in mTOR signaling through the re-purpose of effective anti-diabetes therapeutics that target the brain, and 2) minimize the impact of extrinsic mediators of benign to malignant aging transitions, e.g., inflammatory states, obesity, systemic insulin resistance diseases, and repeated bouts of general anesthesia, by minimizing exposures or implementing neuroprotective measures.

Management of menopause: a view towards prevention

Women spend approximately one-third of their lives with menopause, which occurs around 50 years of age. It is now appreciated that several important metabolic and cardiovascular disease risks emerge during the menopausal transition. Many important conditions occur 10-15 years after menopause, including weight gain and obesity, metabolic syndrome, diabetes, osteoporosis, arthritis, cardiovascular disease, dementia, and cancer; therefore, the occurrence of menopause heralds an important opportunity to institute preventative strategies. These strategies will lead to improved quality of life and decreased mortality. Various strategies are presented for treating symptoms of menopause and diseases that are asymptomatic. Among several strategies is the use of hormone therapy, which has efficacy for symptoms and osteoporosis, and can improve metabolic and cardiovascular health. When instituted early, which is key, in younger postmenopausal women (under 60 years) oestrogen has been found to consistently decrease mortality with a favourable risk-benefit profile in low-risk women. Prospective data show that long-term therapy might not be required for this benefit.

Low estradiol levels escalate menopausal symptoms leading to mild cognitive impairment in postmenopausal women

BACKGROUND Women in menopause experience dramatic alterations in gonadal hormone concentrations, including diminished estradiol levels. It has been hypothesized that these hormonal changes may be responsible for the occurrences of menopausal symptoms, such as hot flushes, sleep disruption, night sweats, and irritability, as well as mild cognitive impairment (MCI) in postmenopausal women. Therefore, this study was aimed to determine if there is any association between hormonal changes and menopausal symptoms, including MCI in postmenopausal women.METHODS A total of 245 postmenopausal women were recruited for this cross-sectional study and classified into 2 groups; MCI and non-MCI groups. Diagnosis of MCI was made using the modified Petersen criteria. Variables such as subjects’ age, duration of menopause, menopausal symptoms, anthropometric status, hormone levels, and cognitive status were assessed and statistically analyzed.RESULTS Of the 245 subjects enrolled in this study, 53.9% had MCI. Multivariate analysis found that sleep disruption and estradiol levels were independent risk factors of MCI in postmenopausal women. No significant correlation was found between menopausal symptoms and estradiol concentration.CONCLUSIONS Low estradiol levels were associated with higher risks of experiencing menopausal symptoms and MCI. Sleep disruption and estradiol levels were the most influential factors in the development of MCI in postmenopausal women.

Multi-angles of smoking and mild cognitive impairment: is the association mediated by sleep duration?

Although the association between cigarette smoking and risk of mild cognitive impairment (MCI) is controversial, most recent studies have shown that this influence is negative. However, it is unknown how multiple factors of smoking affect MCI, and the mechanisms of different smoking factors are not yet clarified. This study will examine the impact of various angles of smoking on MCI and the potential mediating effects of sleep duration on smoking MCI association in the elderly. In the case group, 109 elderly people who met the inclusion criteria were selected, and 123 were selected in the control group. Participant characteristics include sleep duration and a detailed lifetime history of smoking. After adjusting the relevant covariates, higher odds of MCI occurrence were found in ex-smokers/current smokers; moderate/heavy smokers; smokers for 30-44, 45-59 and more than 60 years; smokers with cumulative smoking duration of 30-44 or more than 60 years and smokers with cumulative dose smoking intensity of 200-399 or 400-599 cigarettes monthly. Elderly subjects who had quit smoking for 21 years or longer were found to have lower odds of MCI occurrence. The indirect effects of smoking on MCI via sleep duration were statistically significant, as the ratio of indirect effect to total effect ranged from 0.14 to 0.29. Smoking affects cognitive function through multi-angles of smoking and influences the cognitive function partly via the duration of sleep.

Impact of sociodemographic variables on executive functions

Executive functions (EFs) regulate human behavior and allow individuals to interact and act in the world. EFs are sensitive to sociodemographic variables such as age, which promotes their decline, and to others that can exert a neuroprotective effect.

Insulin Resistance is Associated with Increased Levels of Cerebrospinal Fluid Biomarkers of Alzheimer's Disease and Reduced Memory Function in At-Risk Healthy Middle-Aged Adults

BACKGROUND

Type 2 diabetes is associated with an increased risk for Alzheimer's disease (AD). Regulation of normal insulin function may be important in reducing the prevalence of dementia due to AD, particularly in individuals who harbor genetic risk for or have a parental family history of AD. The relationship between insulin resistance (IR) and AD pathology remains poorly understood, particularly in midlife prior to the onset of clinical metabolic disease or cognitive decline.

OBJECTIVE

We examined associations between IR as indexed by HOMA-IR, cerebrospinal fluid (CSF) biomarkers of AD pathology, and memory in middle-aged adults enriched for AD. We postulated that higher HOMA-IR and APOEɛ4 carriage would be associated with greater CSF AD pathology and poor memory performance.

METHODS

Cognitively asymptomatic middle-aged adults (N = 70, mean age = 57.7 years) from the Wisconsin Alzheimer's Disease Research Center with a parental family history of dementia due to AD underwent lumbar puncture, blood draw, and neuropsychological testing. CSF AD biomarkers including soluble amyloid-β protein precursor β (sAβPPβ), amyloid-β42 (Aβ42), and phosphorylated tau (P-tau181) were examined with respect to HOMA-IR and APOEɛ4 status. Delayed memory performance was examined with respect to HOMA-IR, CSF AD biomarkers, and APOEɛ4 status.

RESULTS

Higher HOMA-IR was associated with higher sAβPPβ and Aβ42 . APOEɛ4 carriers had significantly higher levels of sAβPPα, sAβPPβ, and P-tau181/Aβ42 compared to noncarriers. The concurrent presence of higher HOMA-IR and CSF AD pathology predicted worse delayed memory performance.

CONCLUSION

Overall, the findings suggest that IR and APOEɛ4 are contributing factors to the development of AD pathology in midlife, and provide support for targeting insulin function as a potentially modifiable risk factor for AD.

Active Cigarette Smoking in Cognitively-Normal Elders and Probable Alzheimer's Disease is Associated with Elevated Cerebrospinal Fluid Oxidative Stress Biomarkers

Neurodegenerative diseases and chronic cigarette smoking are associated with increased cerebral oxidative stress (OxS). Elevated F2-isoprostane levels in biological fluid is a recognized marker of OxS. This study assessed the association of active cigarette smoking with F2-isoprostane in concentrations in cognitively-normal elders (CN), and those with mild cognitive impairment (MCI) and probable Alzheimer's disease (AD). Smoking and non-smoking CN (n = 83), MCI (n = 164), and probable AD (n = 101) were compared on cerebrospinal fluid (CSF) iPF2α-III and 8,12, iso-iPF2α-VI F2-isoprostane concentrations. Associations between F2-isoprostane levels and hippocampal volumes were also evaluated. In CN and AD, smokers had higher iPF2α-III concentration; overall, smoking AD showed the highest iPF2α-III concentration across groups. Smoking and non-smoking MCI did not differ on iPF2α-III concentration. No group differences were apparent on 8,12, iso-iPF2α-VI concentration, but across AD, higher 8,12, iso-iPF2α-VI level was related to smaller left and total hippocampal volumes. Results indicate that active cigarette smoking in CN and probable AD is associated with increased central nervous system OxS. Further investigation of factors mediating/moderating the absence of smoking effects on CSF F2-isoprostane levels in MCI is warranted. In AD, increasing magnitude of OxS appeared to be related to smaller hippocampal volume. This study contributes additional novel information to the mounting body of evidence that cigarette smoking is associated with adverse effects on the human central nervous system across the lifespan.

Individually modifiable risk factors to ameliorate cognitive aging: a systematic review and meta-analysis

A number of health and lifestyle factors are thought to contribute to cognitive decline associated with age but cannot be easily modified by the individual patient. We identified 12 individually modifiable interventions that can be implemented during midlife or later with the potential to ameliorate cognitive aging. For ten of these, we used PubMed databases for a systematic review of long-duration (at least 6 months), randomized, controlled trials in midlife and older adults without dementia or mild cognitive impairment with objective measures of neuropsychological performance. Using network meta-analysis, we performed a quantitative synthesis for global cognition (primary outcome) and episodic memory (secondary outcome). Of 1038 publications identified by our search strategy, 24 eligible trials were included in the network meta-analysis. Results suggested that the Mediterranean diet supplemented by olive oil and tai chi exercise may improve global cognition, and the Mediterranean diet plus olive oil and soy isoflavone supplements may improve memory. Effect sizes were no more than small (standardized mean differences 0.11-0.22). Cognitive training may have cognitive benefit as well. Most individually modifiable risk factors have not yet been adequately studied. We conclude that some interventions that can be self-initiated by healthy midlife and older adults may ameliorate cognitive aging.

The NEIL Memory Research Unit: psychosocial, biological, physiological and lifestyle factors associated with healthy ageing: study protocol

Background

Population ageing is a global phenomenon that has characterised demographic trends during the 20th and 21st century. The rapid growth in the proportion of older adults in the population, and resultant increase in the incidence of age-related cognitive decline, dementia and Alzheimer’s disease, brings significant social, economic and healthcare challenges. Decline in cognitive abilities represents the most profound threat to active and healthy ageing. Current evidence suggests that a significant proportion of cases of age-related cognitive decline and dementia may be preventable through the modification of risk factors including education, depressive symptomology, physical activity, social engagement and participation in cognitively stimulating activities. The NEIL Memory Research Unit cohort study was established to investigate factors related to brain health and the maintenance of cognitive function.

Methods

A cohort of 1000 normally ageing adults aged 50 years and over are being recruited to participate in comprehensive assessments at baseline, and at follow-up once every 2 years. The assessment protocol comprises a comprehensive neuropsychological battery, some basic physical measures, psychosocial scales, questionnaire measures related to a range of health, lifestyle and behavioural factors, and a measure of resting state activity using electroencephalography (EEG).

Discussion

The NEIL Memory Research Unit cohort study will address key questions about brain health and cognitive ageing in the population aged 50+, with a particular emphasis on the influence of potentially modifiable factors on cognitive outcomes. Analyses will be conducted with a focus on factors involved in the maintenance of cognitive function among older adults, and therefore will have the potential to contribute significant knowledge related to key questions within the field of cognitive ageing, and to inform the development of public health interventions aimed at preventing cognitive decline and promoting active and healthy ageing.