Friday, August 21, 2026

Medicare advantage beneficiary enrollment decisions following new complex conditions

JAMA Health Forum

About the Study:

In this cohort study of more than 1 million Medicare Advantage beneficiaries, developing a new complex medical condition was associated with higher disenrollment, particularly to traditional Medicare. Disenrollment increased with the number of new conditions and was higher among beneficiaries living in states with Medigap guaranteed issue and community rating protections.

Corresponding Author: Mark K. Meiselbach, PhD, Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, 1812 Ashland Ave, Baltimore, MD 21205 (Mark.meiselbach@jhu.edu).

10.1001/jamahealthforum.2026.2843

To access the embargoed study: Visit our JAMA Network Media Center at this link https://media.jamanetwork.com/

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Editor's Note: Please see the article for additional information, including full author list, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

Journal

JAMA Health Forum

US Out-of-state travel for abortion care before and after the Dobbs v Jackson decision

JAMA Network Open

About the Study:

After Dobbs v Jackson Women’s Health Organization, out-of-state travel to North Carolina for abortion care increased, particularly from more restrictive Southeastern states. Patients also presented at later gestational durations and traveled farther for care, indicating increased logistical barriers after policy changes.

JAMA+ Women's Health

Explore JAMA+ Women's Health for more Women's Health research, commentary, multimedia, and resources from across JAMA Network.

Led by Editor in Chief Linda Brubaker, MD, JAMA+ Women's Health is a curated source of trusted clinical information that advances health care for women worldwide. Dr Brubaker is also a JAMA Deputy Editor.

Corresponding Author: Kelsey B. Loeliger, MD, PhD, Department of Obstetrics and Gynecology, Medical University of South Carolina, 96 Jonathan Lucas St, Charleston, SC 29425 (loeliger@musc.edu).

10.1001/jamanetworkopen.2026.29968

To access the embargoed study: Visit our JAMA Network Media Center at this link https://media.jamanetwork.com/

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/10.1001/jamanetworkopen.2026.29968?guestAccessKey=6586188e-7821-4f12-88e1-fb5677535f94&utm_source=for_the_media&utm_medium=referral&utm_campaign=ftm_links&utm_term=082126

Journal

JAMA Network Open

Brexit reshaped the UK health care workforce but failed to ease doctor shortages

Study finds fewer health care workers arrived from European Union countries after the 2016 Brexit referendum, while increased recruitment from elsewhere did not prevent physician vacancies from rising

Harvard Pilgrim Health Care Institute

BOSTON, MA - The United Kingdom's vote to leave the European Union (EU) was associated with major changes in health care worker migration and worsening physician shortages in England, according to a new study published in JAMA Health Forum.

Researchers found that the 2016 Brexit referendum led to an immediate decline in doctors and nurses arriving from EU countries. Although recruitment from non-EU countries increased in the following years, physician vacancies in England's National Health Service (NHS) continued to grow.

Like many high-income countries, the UK relies on internationally trained health professionals to meet workforce needs. Before Brexit, health care workers from EU countries could move relatively freely to the UK. Researchers examined how the 2016 Brexit referendum affected migration patterns and workforce shortages.

Researchers from the Harvard Pilgrim Health Care Institute, Massachusetts General Hospital, London South Bank University, and the WHO Europe Human Resources for Health Group analyzed health workforce data from 2008 to 2019, including more than 418,000 physicians and 358,000 nurses who migrated to Organization for Economic Co-operation and Development (OECD) countries. The study used quasi-experimental methods, such as a controlled interrupted time series design, to compare the UK with 32 high-income OECD countries from before to after the 2016 referendum.

The Brexit referendum was associated with an immediate drop of about 825 physicians and 2,771 nurses arriving from EU countries in 2016. In subsequent years, immigration from non-EU countries rose by an estimated 3,110 physicians and 1,437 nurses annually. Despite those gains, England’s NHS physician vacancies increased by an estimated 383 positions, while overall nurse immigration declined.

“The Brexit referendum changed where the United Kingdom recruited its health care workforce, with fewer clinicians arriving from Europe and more from countries in Africa and Asia. Our findings show that these shifts were not enough to prevent growing physician shortages within the National Health Service,” said lead author Tarun Ramesh and research fellow at the Harvard Pilgrim Health Care Institute.

The researchers also found that migration from EU countries began declining well before the UK's formal withdrawal from the European Union in 2020, with important implications for health care workforce planning.

“Health care workforce migration is highly sensitive to policy signals. Even before the UK formally left the European Union, uncertainty surrounding future immigration rules was associated with substantial changes in the flow of doctors and nurses into the country,” said senior author Hao Yu, Harvard Medical School associate professor of population medicine at the Harvard Pilgrim Health Care Institute.

The researchers say policymakers considering immigration restrictions should weigh the potential effects on health care staffing and access to care, as well as the risk of growing reliance on clinicians from countries that may already face their own workforce shortages.

Manuscript information

Ramesh T, Leary A, Zhang F, Yu H. Health Workforce Immigration to the United Kingdom after the Brexit Referendum. JAMA Health Forum. Published online August 21, 2026.

Research reported in this press release was supported by the National Institute on Minority Health and Health Disparities (R01MD013736), National Institute on Alcohol Abuse and Alcoholism (R01AA031588), and National Institute of Nursing Research (R01NR020859). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

About the Harvard Pilgrim Health Care Institute’s Department of Population Medicine

The Harvard Pilgrim Health Care Institute's Department of Population Medicine is a unique collaboration between Harvard Pilgrim Health Care and Harvard Medical School. Created in 1992, it is the first appointing medical school department in the United States based in a health plan. The Institute focuses on improving health care delivery and population health through innovative research and education, in partnership with health plans, delivery systems, and public health agencies. Follow us on Bluesky and LinkedIn.

Journal

JAMA Health Forum

DOI

10.1001/jamahealthforum.2026.2868

Article Title

Health Care Workforce Immigration to the UK After Its European Union Membership Referendum

Article Publication Date

21-Aug-2026

Health care workforce immigration to the UK after its European union membership referendum

JAMA Health Forum

About the Study:

In this cross-sectional study, the Brexit referendum’s policy uncertainty produced a sustained decline in EU-origin health care worker immigration, partially offset by recruitment from non-EU countries. This substitution did not prevent increases in physician vacancies and persistent nursing shortfalls, underscoring the sensitivity of health workforce supply to migration policy. Policymakers considering similar restrictions should account for anticipatory effects, substitution dynamics, and potential consequences for global health equity.

Corresponding Author: Hao Yu, PhD, Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Landmark Center, 401 Park Dr, Ste 401 East, Boston, MA 02215 (hao_yu@hphci.harvard.edu).

10.1001/jamahealthforum.2026.2868

To access the embargoed study: Visit our JAMA Network Media Center at this link https://media.jamanetwork.com/

https://jamanetwork.com/journals/jama-health-forum/fullarticle/10.1001/jamahealthforum.2026.2868?guestAccessKey=a46956c9-c4d1-46a1-9bdf-cbc90ebe3eab&utm_source=for_the_media&utm_medium=referral&utm_campaign=ftm_links&utm_term=082126

Journal

JAMA Health Forum

Scientists map hair follicle formation in spacetime, advancing understanding of how organs develop

Research findings could inform understanding of how congenital conditions may affect organ development, leading to better diagnosis and treatment

Johns Hopkins Medicine

In a new research report, scientists at Johns Hopkins Medicine say they have developed a technology that allows them to capture a 3D molecular “snapshot” of hundreds of hair follicles as they develop and then reconstruct the fourth dimension — time — to effectively create a stop-motion animation of how this organ forms.

The National Institutes of Health-funded research was published online July 1 and will appear in the Sept. 3 print issue of Cell.

Hair follicles are the smallest, most numerous organs in our body but they form in similar ways as the other organs, the scientists say. This advancement thus paves the way for understanding how organ development may go awry for people with certain congenital conditions.

“Our four-dimensional (4D) map of the hair follicle from mice serves as a model system for understanding broad-stroke fundamentals of how organs develop,” says Reza Kalhor, Ph.D., associate professor of biomedical engineering at the Johns Hopkins University School of Medicine, who led the recent study.

By analyzing the 4D map, the researchers were able to identify distinct phases in this organ’s formation — a complex choreography of thousands of cells. First, the precursor cells organize themselves in space to establish the organ’s spatial axis perpendicular to skin surface. Next, these precursors differentiate into the many cell types needed to form hair follicles. Finally, these new cell types grow and morph into a mature follicle, preparing to produce the hair strand.

The research further compares the hair follicles of normal mice to hairless mice lacking a gene, Foxn1, which is critical for hair growth. This comparison may help scientists understand how medical conditions that cause hair loss develop, which may lead to new ways to prevent and treat hair loss in the future, says Luis Garza, M.D., Ph.D., a professor of dermatology at the Johns Hopkins University School of Medicine and co-author of the paper.

Scientists have long sought out a way to visualize how organs develop over time. Doing so may lead to a better understanding of how certain inherited conditions may affect organ development, or capture how and when tumors develop, and could lead to earlier diagnoses and treatments, Kalhor says.

“This problem remains complicated because organs are generated by millions of cells in very complex, coordinated processes,” says Soichiro Asami, the first author of the paper and a Ph.D. candidate in Kalhor’s lab. “We developed a technology that tackles the problem of visualizing this, and applied it to hair follicles, because there are hundreds of them spanning each stage of organ development.”

Biomedical engineers Kalhor and Asami partnered with Garza, who frequently studies Foxn1 mice as a model for understanding how hair growth disorders develop and to find new ways to treat them. Garza provided key context and background on hair follicle biology and tissue samples from normal and hairless mice in this recent study.

The researchers developed a new molecular imaging tool, 3D DNase-Enhanced Expression Profiling (3DEEP), that allows them to analyze pieces of tissue large enough to capture hair follicle organs in entirety in skin samples of normal mice and bald mice. 3DEEP removes genomic DNA from the skin samples, which can interfere with chemical reactions used to visualize fragile pieces of messenger RNA essential for understanding organ development. From there, the researchers labeled the positions of millions of RNA molecules in the sample, providing a precise, 3D spatial map of gene expression within the tissue.

Then, the scientists classified the cell types in these complex organs, calculated the molecular age of each hair follicle and lined up the hair follicles from youngest to oldest, turning frozen 3D snapshots of the skin of normal and hairless mice into 3D stop-motion animation. Jean Fan, Ph.D., assistant professor of biomedical engineering at Johns Hopkins, created an online interface for exploring and interacting with this animation.

“These tools show us how a hair follicle grows from a tiny thickening of the skin to a deep, matured structure,” says Garza. “It is a window into organogenesis.”

Comparing the maps of hair follicle samples from normal and hairless mice, the scientists say they determined that hair follicles from hairless mice experienced delayed development as they formed. Notably, the cells from hairless mice follicles were able to proliferate, or divide and grow, at a higher rate, but had a reduced ability to mature and take on specific roles at the right time, destabilizing the delicate choreography of the organ’s development, Kalhor says.

“The Foxn1 mutation led to a breakdown in cellular communication and timing, causing the hair follicle organs to structurally collapse before hair had the chance to form,” says Asami.

In the future, Garza says this technique of visualizing hair follicle development has the potential to help researchers understand the cause of certain hair loss conditions in people.

“Eventually if we can apply this technology to people, then we can find out a tremendous amount more from each patient and help individually treat them,” Garza says.

In addition to Asami, Fan, Garza and Kalhor, another Johns Hopkins scientist, Chenshuo Yin, contributed to this paper.

Funding for this research was provided by the National Institutes of Health (R01HG012357, U01HL156056), the Simons Foundation and the David & Lucile Packard Foundation.

Journal

Cell

New insights into autism and the brain

By combining three different brain scans, researchers have gained new insight into the biological mechanisms associated with autism. The findings suggest that the dopamine system may play an important role in autism

University of Southern Denmark Faculty of Health Sciences

How does autism manifest in the brain? Researchers from the University of Southern Denmark and Odense University Hospital have investigated this question in a new study involving 60 adults.

For the first time, they combined three advanced brain-scanning techniques, allowing them to examine the brain’s dopamine system, energy use and communication between brain regions at the same time.

The findings provide a more nuanced picture of the biological mechanisms associated with autism. The study found a higher number of dopamine D2 receptors in autistic people than in neurotypical people, suggesting that the dopamine system may play an important role in autism.

Three brain scans provided a new picture

Previous autism research has primarily focused on how different brain regions communicate with one another, while only a smaller number of studies have examined neurotransmitters or the brain’s energy use.

Because neurotransmitters regulate communication between different regions of the brain, understanding any differences in these chemical messengers is important if we are to better explain why communication between certain brain regions may differ in autistic and neurotypical people.

By bringing all these perspectives together in a single study for the first time, the researchers were able to identify relationships that had not previously been described.

- Our study is the first to investigate the neurotransmitter dopamine, the brain’s energy use (glucose metabolism) and communication between brain regions in the same study. This gives us a more nuanced understanding of the neurobiological mechanisms associated with autism, says Laust Vind Knudsen, postdoc at the Research Unit for Psychiatry, Odense University Hospital and the University of Southern Denmark.

He is first author of the study, which showed, among other things, that certain deep brain regions in autistic people had both higher energy use and more receptors for the neurotransmitter dopamine than in neurotypical participants.

The study was conducted as part of Laust Vind Knudsen´s PhD project at the University of Southern Denmark and Odense University Hospital, under the supervision of Professor Tanja Maria Sheldrick-Michel as research leader and principal supervisor and Professor Manouchehr Seyedi Vafaee as co-supervisor.

The dopamine system appears to function differently

Dopamine is a neurotransmitter that some nerve cells in the brain use to send messages to one another. It plays a role in, among other things, motivation, learning and movement.

The study showed that, among the autistic people who participated, a higher number of dopamine receptors was associated with higher energy use in the same brain regions.

The researchers also found that the dopamine system influenced the communication between brain regions differently in autistic participants than in neurotypical participants.

- Our findings suggest that the dopamine system not only differs between autistic and neurotypical people. They also indicate that the dopamine system affects communication between brain regions differently in the two groups. This suggests that the dopamine system may play a more fundamental role in autism than previously thought, says Laust Vind Knudsen.

New knowledge about biological variation in autism

The researchers emphasise that the study does not explain why autism develops and cannot be used to make a diagnosis. What it does provide is new knowledge about the biological variation and biological mechanisms associated with autism, and about the interplay between the brain’s neurotransmitters, energy use and communication between different brain regions.

The findings are also interesting because many autistic people also have an ADHD diagnosis, and because the dopamine system plays a central role in ADHD.

The findings therefore raise new questions about whether some of the biological mechanisms linked to the dopamine system may be shared by autism and ADHD and could therefore help explain the high prevalence of ADHD among autistic people.

- Brain research can help us understand autism better, not in order to change autistic people, but to create greater understanding of neurodiversity and better conditions in society. Our findings also raise new questions about why autism and ADHD so often occur together, which we would like to investigate further, says Laust Vind Knudsen.

A step along the way

The study included 60 adult participants and is the first positron emission tomography (PET) study specifically designed also to investigate possible differences between autistic men and women.

At the same time, the researchers emphasise that larger studies are needed to determine whether the findings are valid and can be replicated in other cohorts of autistic people.

Facts:

What is dopamine?

Dopamine is a neurotransmitter that nerve cells use to send messages to one another. It plays a role in, among other things, motivation, learning, movement and reward.

For dopamine to work, it must bind to special receivers on nerve cells called receptors. One of these is the D2 receptor, which the researchers examined in this study.

The D2 receptor is an important part of the dopamine system and has previously been linked to, among other things, ADHD and other neurological and psychiatric conditions.

The only FDA-approved medications related to autism specifically affect the dopamine D2 receptor, which is why it was relevant to examine this receptor in the study. These dopamine D2 medications are used to reduce aggression and irritability in autistic children.

What do neurotypical and neurodivergent mean?

Neurotypical is a term used for people whose neurological development and functioning fall within what is considered typical in the general population.

Neurodivergent is a term used for people whose neurological development or functioning differs from what is considered typical. The term includes autism, ADHD, dyslexia and other forms of neurological variation.

Overlap between autism and ADHD

Autistic people often have one or more co-occurring diagnoses, or comorbidities.

It is estimated that around 70% have one comorbidity, while 40% have two or more.

ADHD is one of the most common comorbidities. Studies suggest that around 40% of autistic people also have an ADHD diagnosis.

(Rong, Y. et al. Prevalence of attention-deficit/hyperactivity disorder in individuals with autism spectrum disorder: A meta-analysis. (2021))

About the study

Method

The study included 60 adult participants: 30 autistic and 30 neurotypical participants.

The researchers combined two PET scans and one functional MRI scan to examine the brain’s dopamine system, energy use and communication between different brain regions at the same time.

This is the first time these three measurements have been combined in a single study including autistic participants.

Funding

The Psychiatry Research Fund, Region of Southern Denmark.

Journal

European Journal of Nuclear Medicine and Molecular Imaging

DOI

10.1007/s00259-026-08053-4

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Subcortical dopamine D2 receptor availability and glucose metabolism in autism: a dual-tracer PET/MR study

A secret to survival for California’s most endangered salmon

Chinook need cold water in first weeks for their eggs to survive

NOAA Fisheries West Coast Region

Cross-Section of Salmon Otolith — image:
A slice of an ear bone, or otolith, from a juvenile winter-run Chinook salmon. The otolith measures about the size of the eye of a needle, with daily growth increments that resemble tree rings indicating when the fish hatched. White circles indicate where an ion microprobe measured oxygen isotopes to reconstruct temperatures the fish experienced just before emerging from their gravel nests, called redds.
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Credit: George Whitman/UC Davis Center for Watershed Sciences

Sacramento River winter-run Chinook salmon are California’s most endangered salmon, with a single surviving population and an average of a few thousand returning fish in recent decades. Shasta Dam blocks their original habitat in cold mountain rivers draining Mount Shasta, leaving them to spawn in the low-lying Sacramento River heated by the summer sun.

The research, published this week in Science Advances, found that cool river temperatures in the first 15 days after their eggs were fertilized was crucial for their survival. In warm years with less water, cold water barely covered this critical thermal window, sharply limiting survival in what may become an increasing reality for salmon as the climate warms.

“Salmon may spawn throughout the summer season, but our results suggest that only a small fraction of those spawning events ultimately produced the juveniles that survived,” said Kohma Arai, who authored the research as a postdoctoral scholar at UC Davis with other scientists from the university, NOAA Fisheries, UC Santa Cruz, UCLA, and the Norwegian Institute for Nature Research.

“This helps us understand the connection between what individuals experience during development and how populations respond to environmental change, which is becoming increasingly important as climate change continues to reshape aquatic ecosystems,” he said.

Water managers try to release cold water from Shasta Reservoir to cool the river enough for salmon eggs incubating in river gravel to survive, while also delivering water to farms and cities vital to California’s economy. The balance grows more difficult in low-water years. Water agencies, water users, such as irrigators, and federal and state fish agencies prioritized the new research to address science questions key to salmon survival in a changing climate. The U.S. Bureau of Reclamation and California State Water Board funded the research.

Behind the Spawning

Fisheries biologists long measured the annual success of winter-run Chinook salmon by the number of adult salmon returning upriver to spawn, presuming many were successful. However, laboratory studies suggested eggs may be sensitive to river temperatures. The new research probing that connection shows that in some years the true success of the species may be much more limited.

“We learned that even when surveys show many salmon spawning over an extended season, only those eggs that experience the right temperatures are likely to survive,” said Rachel Johnson, a research scientist at NOAA’s Southwest Fisheries Science Center and University of California Davis who helped lead the research. “In some years, that number can be shockingly small. It’s this number of successful spawners that we need to track to assess the true risk of extinction and goals towards recovery.”

This survival bottleneck can dramatically reduce population size and erode diversity that helps salmon adapt to a changing climate, she said. She cautioned against using the results to target limited cold water to the key 15-day window for only part of the spawning season, favoring a reduced number of redds, or nests.

“Selecting the winners at this life stage can have unintended consequences by narrowing the chance that salmon encounter favorable conditions at later life stages— it’s like putting all your eggs in one basket.” Instead, the findings argue for strategies such as reintroduction to historical habitat that give fish more options to survive, benefiting the environment, tribal communities, and economy in the long run.

“For endangered species, we have removed so many options, we don’t have the luxury of further selecting certain survivors,” Johnson said.

Instrument Examines Ear Bones

The team, for the first time, combined established salmon spawning surveys, river temperature models, and analysis of salmon otoliths, or ear bones, to track the factors affecting juvenile salmon developing inside their eggs. Researchers also collaborated with a UCLA laboratory that operates an ion microprobe, an advanced instrument that measures oxygen isotopes in the otoliths that indicate the temperatures the salmon were exposed to.

By combining those temperature records with salmon hatch dates estimated from otolith growth increments, river temperature models, and spawning surveys, the researchers identified the redds that likely produced the surviving salmon.

When the team compared the incubation temperatures of surviving juveniles to temperatures for spawning areas where juveniles did not survive, “the pattern was remarkably clear,” Arai said. “The juveniles that survived had experienced cooler incubation temperatures during their earliest stages of development, whereas unsuccessful locations were consistently associated with warmer temperatures over the same developmental period.

“That was one of those rare moments in research where the biological story became immediately apparent from the data,” he said.

For each 1.8°F (1°C) increase in the average river temperature during the 15-day thermal window, the probability of juveniles in a redd surviving declined about 73 percent, researchers found.

The fish that survived the narrow thermal window appeared to tolerate higher temperatures later in their development. The findings also suggest that the timing of favorable river temperatures may be as important as the temperatures themselves. Even short mismatches between salmon spawning and available cold water can substantially reduce the number of juveniles that survive.

New Framework Provides Insight

Combining the sensitivity of the ion microprobe with complementary analyses may open a new window on the early development of salmon and other species sensitive to temperatures and changing environmental conditions, the researchers said. It may someday reveal the experiences of individual animals across species and long time periods.

“I will never cease to admire the way our students and researchers see new technology and envision new ways to apply it to answer questions that may have seemed out of reach,” said Carson Jeffres, a senior researcher at UC Davis who leads a fisheries laboratory with Johnson and is a co-author of the new research. “Suddenly we have new insight into the very earliest and—now we know—key stages of salmon survival.”

The researchers praised collaboration with the U.S. Fish and Wildlife Service, which collected juvenile fish for the study; the California Department of Fish and Wildlife, which documented spawning locations in the river; NOAA Fisheries and University of California Santa Cruz, which tracked river temperatures connected to the otolith data; and the UCLA team that focused the ion microprobe on otoliths at very fine scales.

“It is incredibly gratifying to see scientific innovation, collaborative research, and strong agency-academic partnerships come together to identify critical bottlenecks limiting recovery. Those insights allow us to focus conservation actions with our partners where they can make the greatest difference for the species,” Johnson said.

FOR MORE INFORMATION

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