How Modifiable Are Modifiable Dementia Risk Factors? A Framework for Considering the Modifiability of Dementia Risk Factors

Prevalence, deaths and disability-adjusted life years due to Alzheimer's disease and other dementias in Middle East and North Africa, 1990-2021

Alzheimer's disease (AD) ranks among the leading causes of morbidity and mortality worldwide. The objective was to evaluate the burden of AD and other dementias among the countries of the Middle East and North Africa (MENA) region by age and sex from 1990 to 2021. The data were sourced from the Global Burden of Disease (GBD) study 2021. The estimates are presented as counts and age-standardised rates per 100,000 accompanied by 95% uncertainty intervals (UIs). In 2021, AD and other dementias recorded an age-standardised prevalence of 772.7 per 100,000 in the MENA region (95% UI 671.2-877.6 per 100,000). This rate decreased by 4.9% in comparison to 1990, marking a statistically significant change. AD and other dementias also accounted for approximately 73.79 thousand deaths in the region in 2021, with the age-standardised rate decreasing by 8.6% compared to 1990. Moreover, the disability-adjusted life years (DALY) rate was 476.3 per 100,000 population (95% UI 225.6-1004.2), representing a 7.7% decrease from 1990 to 2021. Lebanon registered the highest point prevalence per 100,000 at 828.25, while the United Arab Emirates recorded the lowest at 652.43. The age-standardised point prevalence decreased from 1990 to 2021 in 13 of the MENA countries, while no significant changes were observed in eight of countries. Additionally, in 2021, women experienced higher prevalence rates, DALYs, compared to men. In the MENA region, age-standardised dementia prevalence rose with age in both sexes. The burden of dementia in MENA has decreased from 1990 to 2021, but it remains higher than global estimates. Furthermore, the findings indicate that dementia imposes a greater burden on the female population compared to males. To achieve a more accurate estimation of the burden of Alzheimer's disease and other dementias, more systematic studies in low- to middle-income countries within the MENA region are required.

Predicting the Beneficial Effects of Cognitive Stimulation and Transcranial Direct Current Stimulation in Amnestic Mild Cognitive Impairment with Clinical, Inflammation, and Human Microglia Exposed to Serum as Potential Markers: A Double-Blind Placebo-Controlled Randomized Clinical Trial

In amnestic mild cognitive impairment (aMCI), neuroinflammation evolves during disease progression, affecting microglial function and potentially accelerating the pathological process. Currently, no effective treatment exists, leading to explorations of various symptomatic approaches, though few target the underlying physiological mechanisms. Modulating inflammatory processes may be critical in slowing disease progression. Cognitive stimulation (CS) and transcranial direct current stimulation (tDCS) applied to the left dorsolateral prefrontal cortex (l-DLPFC) show promise, but the results are heterogeneous. Thus, a randomized, double-blind, placebo-controlled clinical trial is currently underway. The first-stage results were examined after three weeks of intervention in two groups: active tDCS combined with CS and sham tDCS combined with CS. Twenty-two participants underwent two assessments: T0 (baseline) and T1 (after 15 sessions of tDCS, active or sham, and 9 sessions of CS). The results demonstrated that CS improved cognition, increased brain-derived neurotrophic factor (BDNF) levels, and reduced peripheral proinflammatory cytokine levels (interleukin IL-6 and chemokine CX3CL1) in serum. This decrease in IL-6 may promote microglial proliferation and survival as a modulatory effect response, while the increase in BDNF might suggest a regulatory mechanism in microglia-neuron interaction responses. However, tDCS did not enhance the cognitive or modulatory effects of CS, suggesting that longer interventions might be required to achieve substantial benefits.

Subclinical hyperthyroidism and the risk of dementia: A meta-analysis

BACKGROUND

Accumulating evidence suggests that thyroid dysfunction may be related to the risk of dementia. However, previous studies evaluating the association between subclinical hyperthyroidism and the risk of dementia showed inconsistent results. This systematic review and meta-analysis were performed to evaluate the relationship between subclinical hyperthyroidism and the incidence of dementia in the general population.

METHODS

Cohort studies relevant were retrieved by searching the electronic databases including PubMed, Web of Science, and Embase. A random-effects model was used to combine the data by incorporating the influence of between-study heterogeneity. Subgroup and meta-regression analyses were performed to investigate the source of heterogeneity.

RESULTS

Nine cohort studies including 49,218 community-derived participants were included. Among them, 3177 (6.5%) had subclinical hyperthyroidism at baseline. During a mean follow-up of 10.2 years, 4044 participants developed dementia. The pooled results showed that compared to the participants with euthyroidism, those with subclinical hyperthyroidism had a higher incidence of dementia (risk ratio: 1.38, 95% confidence interval: 1.09 to 1.74, p = .006; I2 = 47%). Subgroup analyses according to study design, age of the participants, methods for diagnosis of dementia, or analytic model did not significantly change the results. The univariate meta-regression showed that the cutoff of thyroid-stimulating hormone for defining subclinical hyperthyroidism negatively affected the association between subclinical hyperthyroidism and dementia (coefficient: -1.44, p = .009), which completely explained the heterogeneity (residual I2 = 0%).

CONCLUSION

Subjects with subclinical hyperthyroidism may have a higher risk of dementia compared to those with euthyroidism.

Associations between multidomain modifiable dementia risk factors with AD biomarkers and cognition in middle-aged and older adults

This study aimed to determine associations between modifiable dementia risk factors (MDRF), across domains mood symptomatology, lifestyle behaviors, cardiovascular conditions, cognitive/social engagement, sleep disorders/symptomatology, with cognition, beta-amyloid (Aβ) and tau, and brain volume. Middle-aged/older adults (n=82) enrolled in a sub-study of the Healthy Brain Project completed self-report questionnaires and a neuropsychological battery. Cerebrospinal fluid levels of Aβ 1-42, total tau (t-tau), and phosphorylated tau (p-tau181) (Roche Elecsys), and MRI markers of hippocampal volume and total brain volume were obtained. Participants were classified as no/single domain risk (≤1 domains) or multidomain risk (≥2 domains). Compared to the no/single domain risk group, the multidomain risk group performed worse on the Preclinical Alzheimer's Cognitive Composite (d=0.63, p=.005), and Executive Function (d=0.50, p=.016), and had increased p-tau181 (d=0.47, p=.042) and t-tau (d=0.54, p=.021). In middle-aged/older adults, multidomain MDRFs were related to increases in tau and worse cognition, but not Aβ or brain volume. Findings suggest that increases in AD biomarkers are apparent in midlife, particularly for individuals with greater burden, or variety of MDRFs.