NEWS TRENDS ANALYSIS :: THE OBSERVATORY Results from the cognitive tests also


revealed that those who had breastfed, regardless of whether they were de- pressed or not, performed better in all four of the cognitive tests measuring for learning, delayed recall, executive functioning and processing compared to women who had not breastfed. Separate analyses of the data for the depressed and non-depressed groups also revealed that all four cognitive domain scores were significantly as- sociated with breastfeeding in the women who were not depressed. But in the women who were depressed, only two of the cognitive domains — executive functioning and processing speed — were significantly associated with breastfeeding. Interestingly, the researchers also


found that longer time spent breast- feeding was associated with better cog- nitive performance. Women who had breastfed the longest had the highest cognitive test scores.


Scientists identify the cause of Al- zheimer’s progression in the brain


Researchers have used human data to quantify the speed of different processes that lead to Alzheimer’s disease and found that it develops in a very differ- ent way than previously thought. Their results could have important implica- tions for the development of potential treatments, according to a news release from the University of Cambridge.


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The international team, led by the


University of Cambridge, found that instead of starting from a single point in the brain and initiating a chain reaction that leads to the death of brain cells, Alzheimer’s disease reaches different regions of the brain early. How quickly the disease kills cells in these regions, through the production of toxic protein clusters, limits how quickly the disease progresses overall. The researchers used post-mortem brain samples from Alzheimer’s pa- tients, as well as PET scans from liv- ing patients, who ranged from those with mild cognitive impairment to those with late-stage Alzheimer’s dis- ease, to track the aggregation of tau, one of two key proteins implicated in the condition. In Alzheimer’s disease, tau and an- other protein called amyloid-beta build up into tangles and plaques — known collectively as aggregates — causing brain cells to die and the brain to shrink. This results in memory loss, personality changes, and difficulty carrying out daily functions. By combining five different datasets and applying them to the same math- ematical model, the researchers ob- served that the mechanism controlling the rate of progression in Alzheimer’s disease is the replication of aggregates in individual regions of the brain, and not the spread of aggregates from one region to another.


The results, reported in the journal Science Advances, open up new ways of understanding the progress of Al- zheimer’s and other neurodegenerative diseases, and new ways that future treat- ments might be developed. For many years, the processes within the brain which result in Alzheimer’s disease have been described using terms like ‘cascade’ and ‘chain reac- tion.’ It develops over decades, and a definitive diagnosis can only be given after examining samples of brain tissue after death. For years, researchers have relied


largely on animal models to study the disease. Results from mice suggested that Alzheimer’s disease spreads quick- ly, as the toxic protein clusters colonize different parts of the brain. The researchers believe this is the first time that human data has been used to track which processes control the de- velopment of Alzheimer’s disease over time. It was made possible in part by the chemical kinetics approach developed at Cambridge over the last decade which allows the processes of aggregation and spread in the brain to be modeled, as well as advances in PET scanning and improvements in the sensitivity of other brain measurements. The researchers say their methodol-


ogy could be used to help the develop- ment of treatments for Alzheimer’s disease, which affects an estimated 44 million people worldwide.


Fully vaccinated people can contract and pass on COVID-19 at home


Fully vaccinated people can contract and pass on COVID-19 in the home but at lower rates than unvaccinated people. These are the findings of a study of COVID-19 transmission between household contacts, led by Imperial College London and the U.K. Health Security Agency (HSA) and reported in a news release.The study was published in The Lancet Infectious Diseases.


It finds that people who have


received two doses of vaccine have a lower, but still appreciable, risk of becoming infected with the Delta vari- ant in the home compared with people who are unvaccinated. The authors stress that vaccination also reduces the risk of severe illness, hospitaliza- tion and death from COVID-19. The analysis found that around 25% of vaccinated household con- tacts tested positive for COVID-19 compared with roughly 38% of


unvaccinated household contacts. Vaccinated people cleared the infec-


tion more quickly than those who are unvaccinated, but their peak viral load — the greatest amount of SARS-CoV-2 virus found in their nose and throat — was similar to that seen in unvac- cinated people, which may explain why they can still readily pass on the virus in household settings. Despite transmission between


vaccinated people being possible, the researchers say it is essential for people who are unvaccinated, and those who are now eligible for boost- ers, to get vaccinated against COVID- 19 to protect themselves from severe disease and hospitalization. In the study, carried out by the NIHR Health Protection Research Unit in Respiratory Infections at Imperial College London, researchers enrolled 621 participants, identified by the U.K. contact tracing system, between


September 2020 and September 2021, which was before vaccine boosters had become widely available in the U.K. All participants had mild COVID-19 illness or were asymptomatic (show- ing no symptoms) and took swabs from their nose and throat each day for 14-20 days. Of the 621 participants, 163 tested


positive for COVID-19. Whole genome sequencing confirmed that 71 were infected with the Delta variant. The analysis found that viral load declined most rapidly among vac- cinated people infected with the Delta variant compared with unvac- cinated people with Delta, Alpha, or pre-Alpha. However, the peak levels of virus in vaccinated people were similar to those in unvaccinated people. The researchers believe this may explain why the Delta variant is still able to spread despite vaccination.


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