Alzheimer's & other dementias
Accumulating evidence suggests that tau spreads through brain tissue like an infection, traveling from neuron to neuron and turning other proteins into abnormal tangles, subsequently killing brain cells.
Analysis of some old longitudinal studies has found that those carrying the APOE4 gene scored lower on IQ tests during childhood and adolescence. The effect was much stronger in girls than in boys, and affected reasoning most strongly.
IQ scores were lower by 1.91 points for each APOE4 allele carried. But boys scored only an average of 0.33 points lower, while girls scored almost 3 points lower for each APOE4 allele.
Almost all the participants (92%) were white.
Data from a ten-year study involving 345 Alzheimer's patients has found that cholinesterase inhibitors work better with those who don't have the gene CHRFAM7A. The gene is a fusion between a gene that codes for an Alpha 7 receptor for acetylcholine, and a kinase, a type of enzyme. It is not present in the animals genetically engineered to provide Alzheimer's models, but is present in 75% of humans.
Poor sleep has been associated with the development of Alzheimer's disease, and this has been thought to be in part because the protein amyloid beta increases with sleep deprivation. A new study explains more.
Experiments with mice show that sleep deprivation also rapidly increases levels of the other key Alzheimer’s disease protein, tau tangles.
The work built on findings that tau is high in older people who sleep poorly, and that, when people are kept awake all night, their tau levels rise by about 50%.
A small study has found that a 12-week exercise program significantly improved cognition in both older adults with MCI and those who were cognitively healthy, but that effect on blood flow in the brain was different in these two groups.
A Japanese study looking at 128 patients' fecal samples, found that fecal concentrations of ammonia, indole, skatole and phenol were higher in dementia patients compared to those without dementia, while levels of beneficial Bacteroides were lower in dementia patients.
https://www.eurekalert.org/pub_releases/2019-01/aha-it012519.php
A clinical trial involving 9361 older adults (50+) with hypertension but without diabetes or history of stroke has found that intensive control of blood pressure significantly reduced the risk of developing mild cognitive impairment.
While there was also a 15% reduction in dementia, this result did not reach statistical significance. This may have been due to the small number of new cases of dementia in the study groups.
Survey data from 6,807 Danish older adults (average age 60) in the Copenhagen City Heart Study, has found that being distressed in late midlife is associated with a higher risk of dementia in later life.
The survey measured “vital exhaustion”, which is operationalized as feelings of unusual fatigue, increased irritability and demoralization and can be considered an indicator of psychological distress. Vital exhaustion is suggested to be a response to unsolvable problems in individuals' lives, in particular when being incapable of adapting to prolonged exposure to stressors.
Poor sleep has been associated with Alzheimer's disease risk, but a new study suggests a specific aspect of sleep is important.
The study, involving 119 older adults (60+), of whom 80% were cognitively normal and the remainder very mildly impaired, found that decreased slow-wave sleep coincided with higher levels of tau in the brain and a higher tau-to-amyloid ratio in the cerebrospinal fluid.
The APOE gene, the strongest genetic risk factor for Alzheimer’s disease, is known to be involved in cholesterol and lipid metabolism. Now the largest ever genetic study of Alzheimer’s disease, using DNA from more than 1.5 million people, has identified 90 points across the genome that were associated with an increased risk of both cardiovascular disease and Alzheimer’s disease.