Since 2013, undeclared and uncertified exports of fins from five overexploited shark species have been illegal. Now, an international team has determined that illegal fins from four of those species remained prevalent in the market between 2015 and 2021. Among the countries cited as potential violators are Spain, China, and Taiwan. The study is published in the journal Science Advances.

An international consortium has published the most detailed maps to date of brain development in mammals, including mice and humans. According to the researchers, this work provides a detailed outline of how different types of brain cells arise and mature over time, which “will allow us to begin discovering how alterations in this process can lead to disorders such as autism or schizophrenia.” The results are published simultaneously in a set of 12 articles in the journal Nature. 

The Pfizer-BioNTech COVID-19 vaccine has been linked to rare cases of heart inflammation in children and young people. The largest study of these risks in children, published in The Lancet Child & Adolescent Health, concluded that receiving the vaccine is associated with a risk of developing myocarditis or pericarditis within six months of 0.85 additional cases per 100,000 vaccinated children; while after COVID-19 infection, the risk is 2.24 additional cases per 100,000. The study used data from 98% of the British population under the age of 18 (almost 14 million) between January 2020 and December 2022.

The adoption of plant-based diets could reshape agricultural employment worldwide. This is the main conclusion of an international study that estimates that by 2030, between 5% and 28% less agricultural labour would be needed, i.e. between 18 and 106 million fewer full-time jobs. The countries most affected would be those with agriculture based largely on livestock farming, while others, especially low-income countries, could need between 18 and 56 million more workers to grow fruit, vegetables, legumes and nuts. The study is published in The Lancet Planetary Health.

Large language models (LLMs) do not reliably identify people's false beliefs, according to research published in Nature Machine Intelligence. The study asked 24 such models – including DeepSeek and GPT-4o, which uses ChatGPT – to respond to a series of facts and personal beliefs through 13,000 questions. The most recent LLMs were more than 90% reliable when comparing whether data was true or false, but they found it difficult to distinguish between true and false beliefs when responding to a sentence beginning with ‘I believe that’.

Physical inactivity is a risk factor for the onset of Alzheimer's disease. An international team has studied nearly 300 people with preclinical Alzheimer's—without symptoms but with an accumulation of tau and beta-amyloid proteins in the brain—for 14 years to find out whether physical exercise can also influence its progression. The results indicate that even very moderate activity—walking between 3,000 and 5,000 steps per day—was associated with slower deterioration, while the benefits—which appear to be related to lower tau protein deposits—were greater and tended to stabilise with activity involving between 5,000 and 7,500 steps. The results are published in the journal Nature Medicine.

Taking melatonin supplements to treat insomnia for more than a year is associated with an increased risk of heart failure—including an increase in hospitalisations and mortality—within five years of use, according to a study presented at a conference of the American Heart Association. The study compared a group of 65,000 adults diagnosed with insomnia who had a prescription for melatonin with another group who did not have a prescription for this supplement.

An international team, including several Spanish groups and coordinated by the Institute for Bioengineering of Catalonia (IBEC), has developed a pioneering technology that allows for the creation of multiple human kidney organoids, their combination with pig kidneys outside the body, and their successful transplantation back into the same animal. The method could contribute to improving future research and, according to the authors, allows us to envision a future clinical scenario in which organs destined for transplantation can be treated and conditioned before implantation. The work is published in Nature Biomedical Engineering. 

While preparing a systematic review of animal studies on subarachnoid hemorrhage —a particular type of stroke— a Dutch team detected suspicious images and redirected their research: they analyzed 608 publications considered relevant, looking for potential problems with their results. Their findings indicate that 243 (40%) contained duplicate or potentially manipulated images, raising doubts about their reliability. The vast majority (87%) originated in China, and only 22% had been corrected. According to the researchers, these findings “could explain why, despite hundreds of animal studies published in this field, we still lack effective treatments for early brain injury in patients with hemorrhagic stroke”. The results are published in Plos Biology. 

The use of hormonal contraceptives is associated with a small increase in the risk of breast cancer—one additional case of cancer for every 7,752 women who use these drugs—according to a Swedish study. The risk varies depending on the type of hormones administered, and is slightly higher with the use of contraceptives containing desogestrel. The study, published in JAMA Oncology, analyses data from a national registry between 2006 and 2019, with more than two million women aged between 13 and 49.