Medical Bulletin 12/September/2026 - Video

Here are the top medical news for today:

Gut Microbes May Spread Between People More Easily Than Scientists Expected: Study

The gut microbiome may be far more complex than scientists previously thought, with hidden bacterial populations linked to aging, inflammatory bowel disease, colorectal cancer and type 2 diabetes.

Researchers led by the University of Vienna found that common gut bacterial species can contain several genetically distinct populations that have adapted to different conditions inside the gut. The findings, published in Nature, could help scientists identify more precise microbiome markers and eventually develop treatments targeting specific bacterial populations.

The team used an approach called “reverse ecology”, which analyses genetic information to understand how organisms adapt to particular environments. Researchers studied thousands of bacterial isolates from the human gut, along with large metagenomic datasets collected from people in different countries, age groups and health conditions.

Their analysis found that many familiar bacterial species actually contain separate evolutionary lineages. These populations appear to be better suited to different ecological niches within the gut. Some were found more frequently in people with certain diseases or in older individuals, patterns that could remain hidden when researchers examine only the overall bacterial species.

The researchers also found evidence that some highly competitive gut bacterial populations can spread across large geographic distances. In certain cases, these populations appeared to expand across continents within a few decades, suggesting that transmission between people may help shape the gut microbiome alongside diet, medicines and lifestyle.

Scientists say the findings could change how microbiome research links bacteria with disease. Instead of treating an entire species as harmful or beneficial, future studies may focus on specific populations within that species.

Researchers now aim to identify the genes responsible for these differences and understand how they affect bacterial behaviour. Larger studies will be needed to determine whether these populations can reliably predict disease or become targets for personalised microbiome treatments.

REFERENCE: Xiaoqian Annie Yu, Cameron R. Strachan, Craig W. Herbold, Michaela Lang, Christoph Gasche, Athanasios Makristathis, Nicola Segata, Shaul Pollak, Adrian Tett, Martin F. Polz. Genome-wide sweeps create ecological units in the human gut microbiome. Nature, 2026; 655 (8121): 202 DOI: 10.1038/s41586-026-10476-w

Pregnancy Paracetamol Use Linked to Changes in Daughters’ Reproductive Development: Study

Paracetamol use during pregnancy has been linked to differences in reproductive development in baby girls, including smaller ovaries and fewer ovarian follicles, according to a Danish study.

Published in Human Reproduction Open, the prospective observational study examined whether exposure to paracetamol before birth was associated with early markers of reproductive health. Researchers followed 302 three-month-old girls whose mothers had participated in the Copenhagen Analgesic Study.

Among girls exposed to paracetamol during pregnancy, ovarian volume was 40% smaller on average, uterine volume was 13% smaller and the number of ovarian follicles was 23% lower compared with girls who were not exposed. Girls exposed during early fetal development also had lower levels of anti-Müllerian hormone, a marker commonly used to assess ovarian reserve.

The researchers also examined an independent group of 1,210 girls from the Copenhagen Mother-Child Cohort. In this group, prenatal paracetamol exposure was associated with smaller uteruses around puberty and smaller ovaries during adolescence, providing some support for the initial findings.

Girls are born with the ovarian follicles that contain the immature eggs they will have throughout life. These follicles gradually decrease until menopause, making early ovarian development an important area of reproductive research.

However, the study does not prove that paracetamol causes reproductive problems or that exposed girls will have reduced fertility or reach menopause earlier. The researchers stressed that the findings were observed at a population level and cannot predict outcomes for an individual child.

Researchers say longer-term studies are needed to determine whether the observed differences have any effect on fertility or reproductive ageing. They also advised women not to stop medically necessary treatment without consulting a healthcare professional, as untreated fever and severe pain during pregnancy can also pose risks.

REFERENCE: Margit B Fischer, Gylli Mola, et al.; Fetal exposure to paracetamol is associated with altered markers of ovarian development and reduced uterine volume in girls: the COPANA study, Human Reproduction Open, 2026,://doi.org/10.1093/hropen/hoag073

Excessive Light at Night May Change Heart Structure and Function

Too much light at night may be linked to changes in the heart’s structure and function, with a new study finding differences among more than 11,000 people.

Published in the European Heart Journal, the study used data from 11,071 UK Biobank participants. Researchers of Tulane University asked participants to wear wrist-based light sensors for seven days to measure their nighttime light exposure. About three years later, participants underwent cardiac MRI scans to assess the heart.

Researchers compared people exposed to more than three lux of light at night with those exposed to almost no nighttime light. The higher-exposure group had thicker walls in the left ventricle, one of the heart’s main pumping chambers. This reduced the space inside the chamber.

The researchers also found signs that the heart muscle was less able to relax and change shape during a heartbeat. Changes were also observed in the right ventricles and the left atrium, suggesting that nighttime light exposure may be associated with broader changes in cardiac structure and function.

These structural changes are known as cardiac remodelling. They can occur when the heart adapts to prolonged stress or injury and, over time, may contribute to impaired heart function.

However, the study was observational, meaning it can identify an association but cannot prove that nighttime light directly causes heart damage. Other factors linked to both light exposure and cardiovascular health may also contribute to the findings.

Researchers said the results add to previous evidence connecting nighttime light exposure with cardiovascular disease and suggest that reducing exposure could become part of heart-health strategies.

Experts recommend keeping bedrooms as dark as possible, using warmer and dimmer lights after sunset, limiting bright screen exposure at night and covering unnecessary electronic lights. Larger studies are needed to determine whether reducing nighttime light can directly improve cardiovascular health.

REFERENCE: Jin Dai, Wen Dai, et al.; Nighttime light exposure and cardiac structure and function; European Heart Journal; 2026; DOI; 10.1093/eurheartj/ehag563

Study Links H. pylori Exposure to One in Five Bowel Cancer Cases

Exposure to the stomach bacterium Helicobacter pylori may be linked to around one in five bowel cancer cases worldwide, according to an exploratory study published in eGastroenterology.

Researchers analysed data from 43 studies involving nearly 48.7 million people to examine whether H. pylori infection could contribute to the global burden of bowel cancer. They found that people exposed to the bacterium had about a 1.6-fold higher risk of bowel cancer than those without exposure.

Using global cancer data from 2022, the researchers estimated that around 22% of bowel cancer cases could potentially be attributed to H. pylori exposure. However, the estimated proportion fell to 12% when the analysis was limited to 14 population-based and cohort studies, suggesting that the overall figure should be interpreted cautiously.

The highest estimated proportions were seen in the Western Pacific region and Mongolia, at about 25% and 36%, respectively. China had the largest estimated number of bowel cancer cases potentially linked to H. pylori, at around 139,619.

The analysis also suggested that the association may have become stronger among people born in more recent decades. The estimated proportion rose from 9.5% among people born before 1947 to about 15% among those born between 1963 and 1977.

Interestingly, four observational studies found that H. pylori eradication treatment was associated with a lower bowel cancer risk, but the reduction was observed only after 10 years.

Researchers stressed that the findings do not prove that H. pylori causes bowel cancer. Many other factors, including genetics, age, diet and lifestyle, also influence cancer risk.

They said large, long-term studies and randomised clinical trials are needed to determine whether treating H. pylori can actually prevent bowel cancer. Any widespread eradication strategy would also need to consider antibiotic resistance, treatment side effects and local healthcare capacity.

REFERENCE: Li, Y., et al. (2026). Global and regional burden of colorectal cancer potentially related to Helicobacter pylori exposure: a risk attribution modelling study. eGastroenterology. DOI: 10.1136/egastro-2026-100436.