Effects of metabolic syndrome on language functions in aging

Longitudinal trajectories of metabolic syndrome on different neurocognitive domains: a cohort study from the Taiwan biobank

Metabolic syndrome (MetS) brings considerable effects on cognitive function, but trajectories within remain unclear. We investigated the interactions between distinct MetS components and cognitive domains. A total of 5693 participants from the Taiwan biobank during 2008–2018 were enrolled. Participants were classified as either normal or as having MetS at two time points; i.e., study entry and follow-up. At both the time points, cognitive evaluations using the Mini-Mental State Examination (MMSE) were conducted. The hazard ratios (HRs) of mild cognitive impairment (MCI) and dementia were higher in participants meeting more diagnostic components of MetS. Of the five criteria of MetS, three were significantly associated with MCI and dementia: high blood pressure (MCI: HR = 1.203, p < 0.001; dementia: HR = 1.345, p < 0.001), abdominal obesity (MCI: HR = 1.137, p = 0.006; dementia: HR = 1.442, p < 0.001), and low high-density lipoprotein (HDL) level (MCI: HR = 1.149, p = 0.007; dementia: HR = 1.364, p < 0.001). Of the cognitive domains measured, three were significantly associated with MetS; namely, orientation, language, and visuospatial abilities. Participants who were initially diagnosed with MetS but were normal at follow-up had an HR of 1.374 for dementia (p = 0.019), which was beyond our expectations. The undiminished risk of cognitive decline in subjects returning to normal status illustrated that neural injury caused by MetS takes a long time to get repaired. Consequently, earlier detection and management of adjustable risk factors of MetS should be encouraged to minimize the damage.

Breathe Easy, Speak Easy: Pulmonary Function and Language Performance in Aging

BACKGROUND

This study explored the association between pulmonary function (PF) and older adults' language performance accuracy. Study rationale was anchored in aging research reporting PF as a reliable risk factor affecting cognition among the elderly.

METHODS

180 adult English native speakers aged 55 to 84 years participated in the study. PF was measured through forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio (FFR). Language performance was assessed with an action naming test and an object naming test, and two tests of sentence comprehension, one manipulating syntactic complexity and the other, semantic negation. Greater PF was predicted to be positively associated with all tasks.

RESULTS

Unadjusted models revealed FVC and FEV1 effects on language performance among older adults. Participants with higher FVC showed better naming on both tasks and those with higher FEV1 had better object naming only. In covariate-adjusted models, only a positive FVC-object naming association remained.

CONCLUSION

Findings were discussed in terms of brain oxygenation mechanisms, whereby good PF may implicate efficient oxygenation, supporting neurotransmitter metabolism that protects against neural effects of cerebrovascular risk. Effects on object naming were linked to putative differential oxygenation demands across language tasks.

Association of obesity, diabetes and hypertension with cognitive impairment in older age

Background

Age-related cognitive impairment is rising in prevalence but is not yet fully characterized in terms of its epidemiology. Here, we aimed to elucidate the role of obesity, diabetes and hypertension as candidate risk factors.

Methods

Original baseline data from 3 studies (OCTOPUS, DECS, SuDoCo) were obtained for secondary analysis of cross-sectional associations of diabetes, hypertension, blood pressure, obesity (body mass index [BMI] ≥30 kg/m²) and BMI with presence of cognitive impairment in log-binomial regression analyses. Cognitive impairment was defined as scoring more than 2 standard deviations below controls on at least one of 5–11 cognitive tests. Underweight participants (BMI<18.5 kg/m²) were excluded. Results were pooled across studies in fixed-effects inverse variance models.

Results

Analyses totaled 1545 participants with a mean age of 61 years (OCTOPUS) to 70 years (SuDoCo). Cognitive impairment was found in 29.0% of participants in DECS, 8.2% in SuDoCo and 45.6% in OCTOPUS. In pooled analyses, after adjustment for age, sex, diabetes and hypertension, obesity was associated with a 1.29-fold increased prevalence of cognitive impairment (risk ratio [RR] 1.29; 95% CI 0.98, 1.72). Each 1 kg/m² increment in BMI was associated with 3% increased prevalence (RR 1.03; 95% CI 1.00, 1.06). None of the remaining risk factors were associated with impairment.

Conclusion

Our results show that older people who are obese have higher prevalence of cognitive impairment compared with normal weight and overweight individuals, and independently of co-morbid hypertension or diabetes. Prospective studies are needed to investigate the temporal relationship of the association.

Demographic factors and retrieval of object and proper names after age 70

Purpose

This research aimed to investigate whether demographic factors are similarly related to retrieval of object and proper names.

Methods

The sample included 5,907 individuals above age 70 who participated in the Health and Retirement Study between 2004 and 2012. Participants were asked to name two objects as well as the US President and Vice President. Latent growth curve models examined the associations of age, education, and self-rated health with baseline levels and change trajectories in retrieval.

Results

Age and education were more strongly related to retrieval of proper names than to retrieval of object names, both for baseline scores and for change trajectory. Similar effects of self-rated health emerged for both types of stimuli.

Conclusions

The results show that examining object names and proper names together as indication of cognitive status in the HRS might overlook important differences between the two types of stimuli, in both baseline performance and longitudinal change.

Altered learning, memory, and social behavior in type 1 taste receptor subunit 3 knock-out mice are associated with neuronal dysfunction

The type 1 taste receptor member 3 (T1R3) is a G protein-coupled receptor involved in sweet-taste perception. Besides the tongue, the T1R3 receptor is highly expressed in brain areas implicated in cognition, including the hippocampus and cortex. As cognitive decline is often preceded by significant metabolic or endocrinological dysfunctions regulated by the sweet-taste perception system, we hypothesized that a disruption of the sweet-taste perception in the brain could have a key role in the development of cognitive dysfunction. To assess the importance of the sweet-taste receptors in the brain, we conducted transcriptomic and proteomic analyses of cortical and hippocampal tissues isolated from T1R3 knock-out (T1R3KO) mice. The effect of an impaired sweet-taste perception system on cognition functions were examined by analyzing synaptic integrity and performing animal behavior on T1R3KO mice. Although T1R3KO mice did not present a metabolically disrupted phenotype, bioinformatic interpretation of the high-dimensionality data indicated a strong neurodegenerative signature associated with significant alterations in pathways involved in neuritogenesis, dendritic growth, and synaptogenesis. Furthermore, a significantly reduced dendritic spine density was observed in T1R3KO mice together with alterations in learning and memory functions as well as sociability deficits. Taken together our data suggest that the sweet-taste receptor system plays an important neurotrophic role in the extralingual central nervous tissue that underpins synaptic function, memory acquisition, and social behavior.

Flow-Mediated Dilation and Neurocognition: Systematic Review and Future Directions

BACKGROUND

Previous literature indicates that flow-mediated dilation (FMD) is associated with impaired cognition among patients with stroke. The relationship between FMD and cognition in individuals without cerebrovascular disease has yet to be systematically reviewed.

METHODS

The literature was searched using MEDLINE. Exclusion criteria were as follows: focus on neurological disease (e.g., stroke), animal studies, no quantitative measure of endothelial function or cognition, newborn studies, articles with no original data, and articles that are irrelevant to the topic of interest. Neurocognitive tests were categorized in the following domains: executive function, memory (general, working, episodic/semantic, verbal, visual), global cognitive function, information processing speed, language, psychomotor speed, and visual-spatial ability.

RESULTS

The search yielded 700 articles, of which 10 articles, consisting of 2791 participants, met the criteria for inclusion. Most studies conclude that impaired FMD is associated with poorer neuropsychological functioning, particularly in executive functioning (effect sizes: r = 0.07-0.58) and working memory tasks (effect sizes: r = 0.19-0.39). No association was found between other subdomains of memory and FMD. Visual spatial tasks, information processing speed, language tasks, and global cognition were not associated with FMD overall; however fewer studies examined these domains.

CONCLUSIONS

Even in the absence of cerebrovascular disease, there are links between cognition, particularly executive tasks, and vascular function. Public health implications include the potential value of examining FMD as a predictor of cognitive decline, as well as the potential value of improving cognition through pharmacological and behavioral interventions that improve vascular function. Future studies incorporating neuroimaging measures of cerebral blood flow are warranted.