Fluoride is a naturally occurring mineral that has been shown to strengthen teeth and reduce cavities. Many municipalities add fluoride to their drinking water – called community water fluoridation – as a public health measure to support dental health. In recent years, however, some have claimed that ingesting fluoride can harm children’s IQ.
Researchers at the University of Minnesota led a team that investigated the connection between fluoride in drinking water and children’s IQ to see if these claims had merit. The study, published in PNAS, examined Wisconsin state testing records, archival information about when Wisconsin cities began to fluoridate their water, and data from the Wisconsin Longitudinal Study, which has followed a random sample of 10,317 high school seniors from 1957 through 2026. Key findings include:
There is no evidence supporting a connection between community water fluoridation and children’s IQ.
There is also no evidence supporting a connection between community water fluoridation and cognitive functioning at various points later in life.
Findings confirm evidence published in previous research which also used a national sample, but considered school achievement test scores instead of actual IQ scores.
“Utah, Florida and many municipalities have chosen to remove fluoride from drinking water based on flawed studies that considered the IQ effects of exposure to massive doses of fluoride,” said lead researcher John Robert Warren, a professor in the College of Liberal Arts. “Because levels of fluoride added to municipal drinking water in the U.S. are so much lower, almost all prior evidence from those international studies is not relevant to U.S. public policy debates.”
Future research will continue examining the benefits and harms of adding fluoride to community drinking water.
Study co-author Gina Rumore, co-director of the Demography and Economics of Aging Coordinating Center at the University of Minnesota, noted that these findings “provide no support for the claim that community water fluoridation has any harmful effect on children’s IQ or on adult cognition.”
Thigh muscle fat identified as a potential modifiable risk factor for knee osteoarthritis
Representative axial T1-weighted spin-echo thigh MRI scans in (A) a 61-year-old female participant and (B) a 62-year-old female participant. Both participants were of similar age and body mass index (BMI, calculated as weight in kilograms divided by height in meters squared). Both had Physical Activity Scale for the Elderly scores above the mean score in the study. According to the World Health Organization definition, the participant in B qualified as having abdominal obesity (abdominal circumference ≥ 88 cm). Abdominal circumference is a measure of central obesity that captures fat distribution and serves as an indicator of cardiometabolic health. Compared with the participant in A, the participant in B had a higher proportion of ultra-processed food (UPF) in their diet (87.1% vs 29.5%) and exhibited fattier thigh muscles bilaterally, with Goutallier grade (GG) for all thigh muscles summing to 25 for the participant in A and 38 for the participant in B.
Researchers found that a diet high in ultra-processed foods is associated with higher amounts of fat stored inside thigh muscles, regardless of calorie or fat intake, physical activity or sociodemographic factors in a population at risk for knee osteoarthritis. Results of the study were published in Radiology.
Ultra-processed foods usually have longer shelf lives and can be highly appealing and convenient. They contain a combination of sugar, fat, salt and carbohydrates which affect the brain’s reward system, making it hard to stop eating.
“Over the past decades, in parallel to the rising prevalences of obesity and knee osteoarthritis, the use of natural ingredients in our diets has steadily diminished and been replaced by industrially-processed, artificially flavored, colored and chemically altered food and beverages, which are classified as ultra-processed foods,” said the study’s lead author, Zehra Akkaya, MD, researcher and consultant for the Clinical & Translational Musculoskeletal Imaging group at University of California, San Francisco, Department of Radiology and Biomedical Imaging.
Dr. Akkaya and the research team set out to assess the relationship of ultra-processed food intake and intramuscular fat in the thigh.
For the study, researchers analyzed data from 615 individuals who participated in the Osteoarthritis Initiative who were not yet affected by osteoarthritis, based on imaging. The Osteoarthritis Initiative is a nationwide research study, sponsored by the National Institutes of Health, that helps researchers better understand how to prevent and treat knee osteoarthritis.
“Osteoarthritis is an increasingly prevalent and costly global health issue,” Dr. Akkaya said. “It constitutes one of the largest non-cancer-related health care costs in the United States and around the world. It is highly linked to obesity and unhealthy lifestyle choice.”
Of the 615 individuals, (275 men, 340 women) the average age was 60 years. On average, participants were overweight with a body mass index (BMI) of 27. Approximately 41% of the foods they consumed over the prior year were ultra-processed.
The researchers found that the more ultra-processed foods people consumed, the more intramuscular fat they had in their thigh muscles, regardless of caloric intake.
“In addition to investigating the quality of our modern diet in relationship to thigh muscle composition, in this study, we used widely available, non-enhanced MRI, making our approach accessible and practical for routine clinical use and future studies,” Dr. Akkaya said. “These MRIs do not require advanced or costly technology, which means they can be easily incorporated into standard diagnostic practices.”
Half of answers to evidence based questions “somewhat” or “highly” problematic
A substantial amount of medical information provided by 5 popular chatbots is inaccurate and incomplete, with half of the answers to clear evidence based questions “somewhat” or “highly” problematic, show the results of a study published in the open access journal BMJ Open.
Continued deployment of these chatbots without public education and oversight risks amplifying misinformation, warn the researchers.
Generative AI chatbots have been rapidly adopted across research, education, business, marketing and medicine, with many people using them like search engines, including for everyday health and medical queries, explain the researchers.
To gauge the level of accuracy provided in areas of health and medicine already prone to misinformation, and therefore with consequences for everyday health behaviour, the researchers probed 5 publicly available and popular generative AI chatbots in February 2025: Gemini (Google); DeepSeek (High-Flyer); Meta AI (Meta); ChatGPT (OpenAI); and Grok (xAI).
Each chatbot was prompted with 10 open ended and closed questions in each of 5 categories of cancer, vaccines, stem cells, nutrition, and athletic performance. The prompts were designed to resemble common ‘information-seeking’ health and medical queries and misinformation tropes online and in academic discourse.
And they were developed to ‘strain’ models towards misinformation or contraindicated advice—a strategy increasingly used for stress testing AI chatbots and picking up behavioural vulnerabilities, note the researchers.
Closed prompts required chatbots to provide pre-defined responses, often with one correct answer, that aligned with the scientific consensus. Open ended prompts typically required chatbots to generate multiple responses in list form.
Responses were categorised as non-, somewhat, or highly problematic, using objective pre-defined criteria. A problematic response was defined as one that could plausibly direct lay users to potentially ineffective treatment or come to harm if followed without professional guidance.
The information was scored for accuracy and completeness, and particular attention was given to whether a chatbot presented a false balance between science and non-science based claims, regardless of the strength of the evidence.
Each response was also graded on readability, ranging from whether it was written in easy, plain English, to difficult, academic language, using the Flesch Reading Ease score.
Half (50%) the responses were problematic: 30% were somewhat, and 20% were highly problematic.
Prompt type was influential: open-ended prompts, for example, produced 40 highly problematic responses—significantly more than expected—and 51 non-problematic responses—significantly fewer than expected. The opposite was true of closed prompts.
While the quality of responses didn’t differ significantly among the 5 chatbots, Grok generated significantly more highly problematic responses than would be expected (29/50; 58%). Gemini generated the fewest highly problematic responses and the most non-problematic ones.
The chatbots performed best in the area of vaccines and cancer, and worst in the area of stem cells, athletic performance, and nutrition.
Answers were consistently expressed with confidence and certainty, with few caveats or disclaimers. Out of the total 250 questions, there were only two refusals to answer, both of which came from Meta AI in response to queries about anabolic steroids and alternative cancer treatments.
Reference quality was poor, with an average completeness score of 40%. Chatbot hallucinations and fabricated citations meant that no chatbot provided a fully accurate reference list.
All readability scores were graded as ‘difficult’, equivalent in complexity to suitability for a college graduate.
The researchers acknowledge that they only assessed 5 chatbots and that commercial AI is rapidly evolving, so their findings might not be universally applicable. And not all real-world queries are deliberately adversarial, an approach they took which may have overstated the prevalence of problematic content.
Nevertheless, “Our findings regarding scientific accuracy, reference quality, and response readability highlight important behavioural limitations and the need to re-evaluate how AI chatbots are deployed in public-facing health and medical communication,” they point out.
“By default, chatbots do not access real-time data but instead generate outputs by inferring statistical patterns from their training data and predicting likely word sequences. They do not reason or weigh evidence, nor are they able to make ethical or value-based judgments,” they explain.
“This behavioural limitation means that chatbots can reproduce authoritative-sounding but potentially flawed responses.”
The data chatbots draw on also includes Q&A forums and social media, and scientific content is typically limited to open access or publicly available articles, which comprise only 30–50% of published studies. While this enhances conversational fluency, it may come at the cost of scientific accuracy, advise the researchers.
“As the use of AI chatbots continues to expand, our data highlight a need for public education, professional training, and regulatory oversight to ensure that generative AI supports, rather than erodes, public health,” they conclude.
Patient’s own bone treated and reimplanted in breakthrough procedure
Medical first: Dr Herman Breet, Dr Jadine Du Plessis, and Dr Jaco Viljoen (left to right) performed South Africa’s first liquid nitrogen limb salvage surgery at Netcare Unitas Hospital this week.
Thursday, 16 April 2026: In a South African first, a Centurion-based surgeon has successfully performed a hip and limb salvage procedure using a liquid nitrogen dipping technique.
This pioneering approach, performed at Netcare Unitas Hospital in Tshwane this week, could significantly expand treatment options for certain patients with orthopaedic cancers, particularly those who would typically require removal of the affected bone and its replacement with a large prosthesis.
The operation saved the leg of a 15-year-old boy with Ewing’s sarcoma, an aggressive bone cancer. Standard treatment usually involves removing the cancerous section of bone and replacing it with either a large metal prosthesis or the patient’s own bone after irradiation to destroy cancer cells.
“When I explained that conventional surgery meant no more contact sports, I saw the devastation in his eyes – and in his father’s. That’s when I knew we had to try something different,” recalls Dr Jaco Viljoen, an orthopaedic surgeon with a special interest in orthopaedic oncology.
“I’d been prepared for this exact scenario for ten years. When I mentioned there might be another way – a chance he could play sport again – their faces lit up,” says Dr Viljoen.
During the four-and-a-half-hour procedure, Dr Viljoen led a skilled team in removing a 24-centimetre section of the teenager’s femur (thigh bone) where the cancer had developed. Working alongside Dr Viljoen were assistants Dr Jadine Du Plessis and Dr Herman Breet, anaesthetist Dr Bianca Brits, and scrub nurses Registered Nurse Gloria Kgwete and Enrolled Nursing Assistants Leah Lekoane and Mahlatse Motheta.
The team treated the removed segment by immersing it in liquid nitrogen at -179°C to destroy cancer cells. The bone was then reimplanted, marking the first time this technique had been performed in South Africa.
“This kind of complex surgery is only possible with an exceptional team. Every person in that operating theatre played a crucial role in giving this young man his future back,” Dr Viljoen said.
Ewing’s sarcoma is the second most common bone tumour in children and adolescents, according to a recent study in The Lancet Oncology. This aggressive cancer primarily affects individuals aged 10 to 20, with about 80% of cases diagnosed before the age of 20. It most commonly arises in the long bones of the legs and arms, as well as in the pelvis and chest wall, accounting for 10 to 15% of all bone cancers. Without treatment, the disease progresses rapidly, making early intervention critical.
“A day after surgery, the patient was alert and showed good neurovascular function in the affected leg – promising early signs. He even managed a few assisted steps with his physiotherapist, Leonie De Lange. Follow-up tests will monitor how well the treated bone integrates, and we’re cautiously optimistic about his progress,” comments Dr Viljoen.
“This technique marks a significant departure from standard treatment. The traditional approach would have involved the complete removal of the affected bone, followed by a complex prosthetic reconstruction of the hip, which often limits long-term mobility and rules out a return to contact sports. A second alternative – irradiating the patient’s bone before reimplantation – can compromise bone integrity and increase the risk of non-union, often requiring further surgery. For this keen young rugby and cricket player, preserving his natural bone and joint function was a critical consideration,” he adds.
The ideal solution stemmed from a Japanese technique Dr Viljoen had been holding in reserve. The sophisticated procedure, though developed by specialists in Japan more than a decade ago, is rarely performed worldwide – particularly not in patients with Ewing’s sarcoma – and requires exceptional precision. The extreme cold destroys cancerous tumours while preserving the bone’s architecture, allowing it to heal naturally once reimplanted and secured with surgical pins.
“We’ve effectively preserved his bone and hip joint. His own bone will regenerate and integrate with the surrounding tissue. For a young person, that’s game-changing, as his leg can continue to develop normally.
By preserving his natural anatomy, this procedure offers him the possibility of returning to full activity once healed. This technique offers hope of avoiding amputation in other clinically appropriate patients,” explains Dr Viljoen.
Dr Viljoen previously headed the Tumour, Sepsis and Limb Reconstruction Unit at Steve Biko Academic Hospital. A graduate of the University of Pretoria, he completed his orthopaedic specialisation in 2015 and now practises privately at Netcare Unitas Hospital and Netcare Montana Hospital.
“Dr Viljoen and his colleagues have added another chapter to South Africa’s legacy of medical excellence. But, this is about more than innovation – it’s proof that worldclass orthopaedic care happens right here at home, offering hope to patients facing life-altering conditions such as Ewing’s sarcoma,” adds Dr Erich Bock, managing director of Netcare’s hospital division.
“This is what sets exceptional healthcare apart – seeing the whole person, not just the disease. Dr Viljoen and his team haven’t just treated cancer – they’ve preserved a young man’s dreams. That is the true essence of person centred healthcare,” concludes Dr Bock.
Researchers have found that the absolute effects of anti-amyloid drugs on cognitive decline and dementia severity were absent or trivial
Neurons in the brain of an Alzheimer’s patient, with plaques caused by tau proteins. Credit: NIH
Drugs that target amyloid beta proteins in the brain likely have no clinically meaningful positive effects, while increasing the risk of bleeding and swelling in the brain, a new Cochrane review has found.
People with Alzheimer’s disease have high levels of a protein known as amyloid beta in their brains, detectable before symptoms begin, but its role in disease progression is uncertain. Drugs have been developed to remove these proteins from the brain, under the theory that this would prevent or slow disease progression.
The new review examined data from 17 clinical trials with a total of 20 342 participants, all looking at the impact of anti-amyloid drugs on people with mild cognitive impairment or mild dementia due to Alzheimer’s disease. Proponents of these drugs have theorised that they would be more effective at these earlier stages before the disease has progressed.
Absolute effects “well below clinical threshold”
The research found that the absolute effects of anti-amyloid drugs on cognitive decline and dementia severity were absent or trivial, falling well below established thresholds for the minimum clinically important difference.
“Unfortunately, the evidence suggests that these drugs make no meaningful difference to patients,” said lead author Francesco Nonino, neurologist and epidemiologist at the IRCCS Institute of Neurological Sciences of Bologna, Italy. “There is now a convincing body of evidence converging on the conclusion that there is no clinically meaningful effect. While early trials showed results that were statistically significant, it is important to distinguish between this and clinical relevance. It is common for trials to find statistically significant results that do not translate into a meaningful clinical difference for patients.”
In addition to the absence of clinically meaningful effects, the review found that anti-amyloid drugs likely increase the risk of swelling and bleeding in the brain. This was observed in brain scans without any apparent symptoms for most patients, although any long-term effects remain unclear since reporting of symptoms was inconsistent across trials.
Future research should focus on other pathways
On the basis of the evidence, the authors conclude that future trials targeting amyloid beta removal are unlikely to provide clear benefit to patients. They found that these drugs do successfully remove amyloid proteins from the brain, but this does not translate into meaningful clinical benefit. They recommend that future research on Alzheimer’s treatment should focus on other mechanisms, with numerous studies ongoing in other directions.
“I see Alzheimer’s patients in my clinic every week and I wish I had an effective treatment to offer them,” said senior author Edo Richard, Professor of Neurology at Radboud University Medical Centre. “Existing approved drugs offer some benefit for some patients, but there remains a high unmet need for more effective treatments. Sadly, anti-amyloid drugs do not offer this and bring additional risks. Given the absence of correlation between amyloid removal and clinical benefit, we need to explore other pathways to help address this devastating disease.”
One of the study participants exerts force with their calf muscles while sensors measure electrical activity. (Photo: Ruoli Wang)
Even when people with incomplete spinal cord injuries can walk, everyday functions like standing, balancing or producing steady force may remain difficult. A new study shows why.
Using surface skin electrical sensors, a research team in Sweden identified previously unseen changes in motor coordination that result from incomplete spinal cord injuries (SCI). The study is the first to examine how individual motor units (nerve to muscle connections that create movement) work together in people with SCI.
“Our study reveals, at the cellular level, how the central nervous system adapts to the injury to control movement,” says Ruoli Wang, associate professor in biomechanics at Promobilia MoveAbility Lab, KTH Royal Institute of Technology. She says the researchers’ approach was completely non-invasive.
The study’s lead author, PhD student Zhihao Duan, says the researchers found the nervous system struggles to spread signals smoothly across muscles at low levels of exertion after the injury. And it appears to overcompensate at higher levels of exertion, sending “louder”, less refined signals.
Effect on motor units
Muscles move through hundreds or thousands of motor units, each turning on and off precisely to create smooth force. Composed of a single motor neuron and its connecting muscle fibres, these motor units respond to shared signals from the nervous system, much like different sections of musicians led by an orchestra conductor. That shared input is what allows them to act in coordinated patterns.
To explore how well these units coordinate under the control of the central nervous system, the team examined 25 people (including 10 control participants). They used high-density electromyography (HD-EMG) to measure electrical activity in the functionally similar calf muscles – soleus and gastrocnemius – while volunteers pushed lightly or moderately against a device.
Duan says that at 20% effort, fewer of the motor units in the two calf muscles were working in a shared, coordinated way compared with people without injury. As a result, their movements were shaky and unstable. “They were much less being driven by the same coordinated signal from the nervous system.” he says.
At a higher level of effort (50%) the SCI group showed stronger lowfrequency synchronization between the two muscles. The body loses flexibility and precision in control of the movement. “This could be a sign of the nervous system compensating by sending louder, less refined signals,” Duan says.
Unique insights
“One interesting finding is that after spinal cord injury the nervous system becomes more rigid and less able to change its approach as the muscles work harder. A healthy nervous system on the other hand is able to adapt its strategy as force demands, to adjust the shared neural drive level,” Wang says.
Although the study was limited by a small sample size and challenges in identifying enough motor units per muscle from the skin surface, Wang says the results offer unique insight into how SCI reshapes motor control.
“This finding may open the door to a new rehabilitation biomarker, helping clinicians and researchers design new neurorehabilitation strategies to re-tune the spinal cord control and to restore coordinated neural input,” she says.
A major international collaboration on scientific reliability has been completed and is now presented in three articles in Nature by researchers from institutions including Karolinska Institutet. Around half of previously published research results in the social and behavioural sciences could not be replicated in new experiments.
The research programme, known as SCORE, involved 865 researchers who analysed nearly 3900 scientific articles published between 2009 and 2018 in 62 journals in the fields of criminology, economics, educational science, health sciences, leadership, marketing, organisational behaviour, psychology, political science, public administration and sociology.
In three studies published in Nature, different methods were used to investigate whether the research results are reliable. The questions addressed were whether the results can be reproduced, whether they are robust, and whether they can be replicated.
Replication involves testing the same research question, but with new data. In the replication study, the researchers analysed 164 previously published results in the social and behavioural sciences. Of these, just under half, 49%, could be replicated with a similar result to that of the original study.
Open data is key
In the reproducibility study, the same analysis was carried out on the same data. Reproducibility was hampered by the fact that data was often unavailable; only just under a quarter of the articles studied had shared their data openly. Of the 143 articles analysed, 74% could be reproduced to an approximate degree, and 54% to an exact degree. When the original data and code were shared, these figures increased to 91 and 77%, respectively.
“This shows that transparency is key to achieving credible research results,” says Gustav Nilsonne, associate professor of neuroscience at Karolinska Institutet, who co-led the robustness study and is a co-author of all three papers. “Sharing research data enables outsiders to assess which results are reliable.”
In the robustness study, alternative analyses were tested on the same data in 100 different articles. For each article, at least five researchers analysed the same hypothesis using the same data, but with the analysis method they deemed to be the best.
Same conclusion in most cases
Only a third of the new analyses yielded results very close to those reported in the original study. However, three out of four analyses reached the same overall conclusion as the original article. But in about a quarter of the cases, no clear effects were found at all, and in a few cases (around two per cent), the results pointed in the opposite direction.
“This is the world’s largest research project to date investigating the reliability of reported scientific results, and an example of how large-scale collaborations can address questions that no single research group could answer alone,” concludes Gustav Nilsonne. “I hope we will see systematic replication attempts in more fields of research in the future.”
The collaboration was led by the Center for Open Science and researchers at Pennsylvania State University, TwoSix Technologies, the University of Southern California and Eötvös Loránd University. The programme was funded by the US research council DARPA.
A patient with a knee replacement undergoing an MRI where modern technology reduces the distortions in the images.
It is a common concern for patients that metal implants, such as hip or knee replacements, may prevent them from having an MRI scan. In most cases, this is not true. Patients with modern joint replacements can safely undergo MRI, depending on the materials used in the implant. It is important to inform the radiology team about the implant before your scan.
Dr Jean de Villiers, a radiologist and director of SCP Radiology, answers some of the questions most frequently asked by patients, specifically around the process from referral to reporting in radiology imaging.
What is Magnetic Resonance Imaging (MRI)?
MRI is a non‑invasive imaging technique that uses powerful magnets and radio waves to create detailed images of the body’s internal structures. Unlike X‑rays or CT scans, MRI does not involve ionising radiation and is used extensively to diagnose a wide range of conditions.
Because MRI uses strong magnetic fields, many patients ask whether it is safe to have an MRI after a hip or knee replacement.
Can you have an MRI after a hip or knee replacement?
Yes, you can have an MRI scan on other parts of the body, as well as on the knee or hip where the implant is. Although some older MRI scanners may not be compatible with certain prostheses, the vast majority of MRI equipment in use today is safe and compatible with modern hip and knee implants.
How safe is MRI if the implant is made of metal?
Most implants are made from titanium or cobalt‑chromium alloys. Although these materials are metallic, they are not significantly affected by the magnetic field of an MRI scanner, nor do they heat up during the scan. Many implants also contain hard plastic components, all of which are designed to be compatible with MRI scanners. They are not attracted to the powerful magnet in the same way as older or highly magnetic materials.
Dr de Villiers explains, “The vast majority of joint replacements used today are MRI‑safe. The key is that we know about them in advance, so we can adjust the scan if needed.”
What is the main challenge with MRI and an implant?
The main challenge is image quality. Metal can sometimes cause image distortion, known as artefact, on MRI images. This may make it more difficult to assess structures close to the implant. However, modern MRI techniques have improved significantly and can often minimise these effects, allowing radiologists to assess surrounding tissues such as muscles and ligaments, and to detect complications such as infection or loosening. MRI is often the best imaging method for evaluating pain or complications after joint replacement surgery.
What happens if MRI does not produce clear diagnostic images?
In some cases, alternative imaging techniques such as CT or ultrasound may be recommended, depending on the clinical question. However, MRI remains safe and highly valuable for many patients with joint prostheses.
Are there implants that prevent you from having an MRI?
Certain implants and devices may be unsafe or require special precautions during MRI, including:
Implanted pacemakers
Intracranial aneurysm clips
Cochlear implants
Certain prosthetic devices
Implanted drug‑infusion pumps
Neurostimulators
Bone‑growth stimulators
Any other iron‑based metal implants
MRI is also contraindicated in the presence of some internal metallic objects such as bullets or shrapnel, as well as certain surgical clips, pins, plates, screws, metal sutures or wire mesh.
Having a hip or knee replacement does not automatically exclude you from having an MRI scan. With modern implants and appropriate planning, MRI is both a safe and important diagnostic tool. As technology continues to evolve, future developments are expected to further enhance MRI compatibility with hip and knee implants, making it an even more reliable tool for ongoing patient care.
It is crucial for patients to inform their healthcare providers about their joint replacement before undergoing an MRI. This allows the medical team to adjust the MRI settings and take appropriate precautions to ensure both safety and diagnostic accuracy.
Exposure to a chemical commonly used to make plastic more flexible may have contributed to about 1.97 million preterm births in 2018 alone, or more than 8 percent of the world’s total, a new analysis of population surveys shows. The chemical was also linked to the deaths of 74 000 newborns, the researchers further estimate.
The toxin, di-2-ethylhexylphthalate (DEHP), is part of a group of chemicals called phthalates, which appear in cosmetics, detergents, bug repellents, and other household products. Experts have found that these substances can break down into microscopic particles and enter the body through food, air, and dust.
Led by NYU Langone Health researchers, the new study focused on preterm birth, which is a major risk factor for lasting learning and developmental issues and is a leading cause of infant death, according to the World Health Organization.
The new analysis provides the first global estimate of preterm births connected to exposure to DEHP and explores which parts of the world are most affected, according to the authors. A report on the findings published online March 31 in the journal eClinicalMedicine.
“By estimating how much phthalate exposure may contribute to preterm birth worldwide, our findings highlight that reducing exposure, especially in vulnerable regions, could help prevent early births and the health problems that often follow,” said study lead author Sara Hyman, MS.
Past studies have linked DEHP exposure to cancer, heart disease, and infertility, among many other health concerns, added Hyman, an associate research scientist at NYU Grossman School of Medicine. There is also a large body of research connecting the chemical to preterm birth.
According to the new work, DEHP exposure may have contributed to 1.2 million years lived with disability, a measure of all the years that people have lived or will live with illnesses, injuries, and other health issues caused by being born prematurely.
Hyman said that while the phthalate is in widespread use, certain regions are estimated to bear a much larger share of the health impacts than others, with the Middle East and South Asia representing 54 percent of estimated illness from preterm birth. These areas have rapidly growing plastics industries and high levels of global plastic waste.
Africa, which accounted for 26 percent of health problems from DEHP-linked preterm birth, has a disproportionate share of deaths compared with its share of overall premature cases. The researchers said this reflects the region’s higher underlying death toll from preterm birth.
For the study, the research team estimated DEHP exposure in 2018 across 200 countries and territories by pulling data from large national surveys in the United States, Europe, and Canada. They also used estimates from earlier investigations to fill in regions that did not have their own data.
The team then drew on earlier research that assessed how phthalate exposure may affect preterm birth and combined those findings with their global exposure estimates. Finally, they combined this information with worldwide figures on preterm births and deaths to gauge what share of these outcomes might be linked to DEHP.
The scientists repeated these steps for another phthalate called diisononyl phthalate (DiNP), a common replacement for DEHP. According to the results, DiNP may pose a similar risk as DEHP, having contributed to about 1.88 million preterm births around the world. The financial costs associated with newborn deaths ranged from millions to hundreds of billions of dollars for both phthalates.
“Our analysis makes clear that regulating phthalates one at a time and swapping in poorly understood replacements is unlikely to solve the larger problem,” said study senior author Leonardo Trasande, MD, MPP, Professor of Pediatrics at NYU Grossman School of Medicine. “We are playing a dangerous game of Whac-A-Mole with hazardous chemicals, and these findings highlight the urgent need for stronger, class-wide oversight of plastic additives to avoid repeating the same mistakes.”
In addition, because there is some uncertainty in the data, the researchers looked at a range of possible values rather than just one estimate. This uncertainty range showed that the true impact of DEHP could be up to four times smaller than the main estimate or slightly higher. Even under the most conservative estimates, the results point to a substantial health burden, said Hyman.
Despite the limits of this kind of global modelling, added Hyman, the work lays important groundwork for future studies to confirm and refine these results and begins to fill a major gap in understanding the extent to which plastic chemicals affect preterm birth worldwide.
An anterior cruciate ligament injury is a serious knee injury that often affects young, physically active people. On April 30, Dzan Rizvanovic will defend his thesis “Anterior cruciate ligament reconstruction: rationale for graft choice and treatment of associated injuries” in which he has investigated how treatment choice affects outcomes after ACL reconstruction.
“An anterior cruciate ligament injury (ACL injury) is a serious knee injury that primarily affects young and physically active individuals and can have long-term consequences for knee function, work capacity, and quality of life. Each year, a large number of patients in Sweden undergo surgical reconstruction of the injured ligament (ACL reconstruction), and this is the focus of my thesis”, says Dzan Rizvanovic, doctoral student at the Sports Medicine research group at the Department of Molecular Medicine and Surgery, Karolinska Institutet and specialist in orthopaedic surgery at Capio Artro Clinic.
“Using data from the Swedish Knee Ligament Registry, we studied tens of thousands of patients to investigate which factors are associated with different treatment strategies, and how these in turn relate to patients’ perceived knee function and the need for further surgery (revision). The thesis also has a particular focus on how the surgical volume of both the surgeon and the clinic is associated with treatment choices and outcomes”.
Which are the most important results?
“The main findings show that treatment strategies in ACL reconstruction are not solely related to the patient’s injury, but also to organizational factors. Surgeons and clinics with higher surgical volume are more likely to use different types of grafts (tendons used to replace the injured ligament), which may increase the opportunity for individualized treatment. They also repair meniscal injuries more frequently, a strategy that has been shown to be beneficial for long-term knee health. The management of cartilage injuries is also partly influenced by surgical volume”.
“Patients operated on by high-volume surgeons report better knee function two years after surgery and experience shorter waiting times from injury to surgery as well as shorter operative times. In contrast, the need for additional ACL reconstruction in the same knee is more related to patient- and injury-factors than to surgical volume”.
“The thesis also shows that graft choice influences subjective knee function at two years after surgery, particularly among females, which is an important finding”.
How can this new knowledge contribute to the improvement of people’s health?
“This knowledge can contribute to more equitable and individualised care. By clarifying how surgical experience and surgical volume are associated with treatment decisions and outcomes, healthcare systems can better organise resources and create conditions for strengthened competence and improved decision-making in ACL reconstruction”.
“The results can also be used in the dialogue between patient and surgeon to select the treatment that best matches the individual’s needs and circumstances, which in the long term may improve knee function and increase quality of life in this young and working-age population”.
“Furthermore, the results from this thesis highlight the need for discussion regarding clearer national guidelines for referral pathways, minimum surgical volume requirements, and follow-up of treatment outcomes. It is also important that reporting to national quality registers is complete and made mandatory in order to enable transparency and continuous quality improvement”.
What are your future ambitions?
“I hope to continue combining research with my clinical work to drive development forward and contribute to ensuring that patients with knee and sports-related injuries receive the best possible treatment. I also aim to contribute to a more equitable organization of healthcare, in which access to the right expertise at the right time does not depend on where in the country a patient lives”, says Dzan Rizvanovic.
Dissertation
The dissertation seminar will be held on Thursday, April 30th 2026 at 09:00, CIFU, Capio Artro Clinic, Valhallavägen 91, lecture hall house R. The doctoral thesis has been supervised by Anders Stålman.
Thesis
Rizvanovic, Dzan (2026). Anterior cruciate ligament reconstruction : rationale for graft choice and treatment of associated injuries. Karolinska Institutet. Thesis. https://doi.org/10.69622/31333828.v1
