Ischaemic and haemorrhagic stroke. Credit: Scientific Animations CC4.0
Cervical artery dissection is a tear in an artery in the carotid or vertebral artery, and can result in blood clots that cause stroke. A new study has found almost a five-fold increase in the number of U.S. hospitalisations for cervical artery dissection over a 15-year period. The study is published on April 2, 2025, online in Neurology®, the medical journal of the American Academy of Neurology (AAN).
A dissection in the artery wall is most often caused by trauma due to motor vehicle accidents but can also occur with smaller injuries. Heavy lifting has also been shown to cause dissection in some people.
“Cervical artery dissection is an important cause of stroke, especially in people under 50, so it is crucial to detect it right away,” said Shadi Yaghi, MD, of Brown University in Providence, Rhode Island. “Strokes that are not fatal can lead to long-term disability, poor mental health and reduced quality of life. Our research found a dramatic increase in the number of hospitalisations for cervical artery dissection with rates rising steadily year over year.”
For the study, researchers reviewed 15 years of U.S. health data to identify 125 102 people hospitalised for cervical artery dissection. Participants had an average age of 51, and just over half had a stroke at the same time as dissection. Of all participants, 65% were white, 10% were Black, 8% were Hispanic, 3% were Asian or Pacific Islander, and 14% were of other racial groups. Researchers compared the number of hospitalisations to U.S. Census data to determine the annual rate of cervical artery dissections. They then calculated the average annual percentage change in those rates.
Researchers found the number of dissections increased from 11 cases per one million people in 2005 to 46 cases per one million people in 2019, with an average annual increase of 10%. Results were similar for both female and male participants. The average annual increase for Hispanic participants was 16%; for Black participants it was 13%, Asian participants, 12% and white participants, 8%.
Researchers also found a greater average annual increase among people 65 and older at 12% compared to 8% for people under 65.
“Possible reasons for this nearly five-fold increase over 15 years include greater awareness of cervical artery dissection by health care professionals, better access to imaging to help identify it and an overall increase in this condition for which a cause has yet to be determined,” said Yaghi. “Given the rising incidence of cervical artery dissection, our study underscores the importance of finding prevention strategies as well as new treatments to reduce the risk of stroke.” A limitation of the study was that the hospital admission data does not include undiagnosed or untreated cases, so the number of cases may be even higher.
An unusual public health policy in Wales may have produced the strongest evidence yet that a vaccine can reduce the risk of dementia. In a new study led by Stanford Medicine, researchers analysing the health records of Welsh older adults discovered that those who received the shingles vaccine were 20% less likely to develop dementia over the next seven years than those who did not receive the vaccine.
The remarkable findings, published April 2 in Nature, support an emerging theory that viruses that affect the nervous system can increase the risk of dementia. If further confirmed, the new findings suggest that a preventive intervention for dementia is already close at hand.
Lifelong infection
Shingles, a viral infection that produces a painful rash, is caused by the same virus that causes chicken pox — varicella-zoster. After people contract chicken pox, usually in childhood, the virus stays dormant in the nerve cells for life. In people who are older or have weakened immune systems, the dormant virus can reactivate and cause shingles.
Dementia affects more than 55 million people worldwide, with an estimated 10 million new cases every year. Decades of dementia research has largely focused on the accumulation of plaques and tangles in the brains of people with Alzheimer’s, the most common form of dementia. But with no breakthroughs in prevention or treatment, some researchers are exploring other avenues — including the role of certain viral infections.
Previous studies based on health records have linked the shingles vaccine with lower dementia rates, but they could not account for a major source of bias: People who are vaccinated also tend to be more health conscious in myriad, difficult-to-measure ways. Behaviors such as diet and exercise, for instance, are known to influence dementia rates, but are not included in health records.
“All these associational studies suffer from the basic problem that people who get vaccinated have different health behaviours than those who don’t,” said Pascal Geldsetzer, MD, PhD, assistant professor of medicine and senior author of the new study. “In general, they’re seen as not being solid enough evidence to make any recommendations on.”
Markus Eyting, PhD, and Min Xie, PhD, postdoctoral scholars in primary care and population health, are the study’s co-lead authors.
A natural experiment
But two years ago, Geldsetzer recognized a fortuitous “natural experiment” in the rollout of the shingles vaccine in Wales that seemed to sidestep the bias. The vaccine used at that time contained a live-attenuated, or weakened, form of the virus.
The vaccination program, which began Sept. 1, 2013, specified that anyone who was 79 on that date was eligible for the vaccine for one year. (People who were 78 would become eligible the next year for one year, and so on.) People who were 80 or older on Sept. 1, 2013, were out of luck — they would never become eligible for the vaccine.
These rules, designed to ration the limited supply of the vaccine, also meant that the slight difference in age between 79- and 80-year-olds made all the difference in who had access to the vaccine. By comparing people who turned 80 just before Sept. 1, 2013, with people who turned 80 just after, the researchers could isolate the effect of being eligible for the vaccine.
The circumstances, well-documented in the country’s health records, were about as close to a randomized controlled trial as you could get without conducting one, Geldsetzer said.
The researchers looked at the health records of more than 280 000 older adults who were 71 to 88 years old and did not have dementia at the start of the vaccination program. They focused their analysis on those closest to either side of the eligibility threshold — comparing people who turned 80 in the week before with those who turned 80 in the week after.
“We know that if you take a thousand people at random born in one week and a thousand people at random born a week later, there shouldn’t be anything different about them on average,” Geldsetzer said. “They are similar to each other apart from this tiny difference in age.”
The same proportion of both groups likely would have wanted to get the vaccine, but only half, those almost 80, were allowed to by the eligibility rules.
“What makes the study so powerful is that it’s essentially like a randomised trial with a control group — those a little bit too old to be eligible for the vaccine — and an intervention group — those just young enough to be eligible,” Geldsetzer said.
Protection against dementia
Over the next seven years, the researchers compared the health outcomes of people closest in age who were eligible and ineligible to receive the vaccine. By factoring in actual vaccination rates — about half of the population who were eligible received the vaccine, compared with almost none of the people who were ineligible — they could derive the effects of receiving the vaccine.
As expected, the vaccine reduced the occurrence over that seven-year period of shingles by about 37% for people who received the vaccine, similar to what had been found in clinical trials of the vaccine. (The live-attenuated vaccine’s effectiveness wanes over time.)
This huge protective signal was there, any which way you looked at the data.”
By 2020, one in eight older adults, who were by then 86 and 87, had been diagnosed with dementia. But those who received the shingles vaccine were 20% less likely to develop dementia than the unvaccinated.
“It was a really striking finding,” Geldsetzer said. “This huge protective signal was there, any which way you looked at the data.”
The scientists searched high and low for other variables that might have influenced dementia risk but found the two groups to be indistinguishable in all characteristics. There was no difference in the level of education between the people who were eligible and ineligible, for example. Those who were eligible were not more likely to get other vaccinations or preventive treatments, nor were they less likely to be diagnosed with other common health conditions, such as diabetes, heart disease and cancer.
The only difference was the drop in dementia diagnoses.
“Because of the unique way in which the vaccine was rolled out, bias in the analysis is much less likely than would usually be the case,” Geldsetzer said.
Nevertheless, his team analyzed the data in alternate ways — using different age ranges or looking only at deaths attributed to dementia, for example — but the link between vaccination and lower dementia rates remained.
“The signal in our data was so strong, so clear and so persistent,” he said.
Stronger response in women
In a further finding, the study showed that protection against dementia was much more pronounced in women than in men. This could be due to sex differences in immune response or in the way dementia develops, Geldsetzer said. Women on average have higher antibody responses to vaccination, for example, and shingles is more common in women than in men.
Whether the vaccine protects against dementia by revving up the immune system overall, by specifically reducing reactivations of the virus or by some other mechanism is still unknown.
Also unknown is whether a newer version of the vaccine, which contains only certain proteins from the virus and is more effective at preventing shingles, may have a similar or even greater impact on dementia.
Geldsetzer hopes the new findings will inspire more funding for this line of research.
“At least investing a subset of our resources into investigating these pathways could lead to breakthroughs in terms of treatment and prevention,” he said.
In the past two years, his team has replicated the Wales findings in health records from other countries, including England, Australia, New Zealand and Canada, that had similar rollouts of the vaccine. “We just keep seeing this strong protective signal for dementia in dataset after dataset,” he said.
But Geldsetzer has set his sights on a large, randomized controlled trial, which would provide the strongest proof of cause and effect. Participants would be randomly assigned to receive the live-attenuated vaccine or a placebo shot.
“It would be a very simple, pragmatic trial because we have a one-off intervention that we know is safe,” he said.
Geldsetzer is seeking philanthropic funding for the trial as the live-attenuated vaccine is no longer manufactured by pharmaceutical companies.
And such a trial might not take long to see results. He pointed to a graph of the Wales data tracking the dementia rates of those who were eligible and ineligible for the vaccine. The two curves began to separate in about a year and a half.
The idea that autism is caused by vaccines has recently been revived by Robert F. Kennedy Jr., the presumptive nominee for US Secretary of Health and Human Services, as well as by president-elect Donald Trump. When asked about vaccines at a recent press conference, Trump reportedly said there was “something wrong” with rising autism rates, adding: “We’re going to find out about it.”
From a research perspective, there is little left to discover about vaccines used in long-standing nationwide vaccine programmes, such as diphtheria, tetanus, whooping cough, polio, measles, mumps and rubella. There is strong data from different countries showing that these vaccines do not cause autism or underlie the vast increase in autism diagnosis rates. So why do suspicions that vaccines cause autism remain?
1. Unawareness of evidence
Reliably and accurately communicating research results to the public is difficult. Research results usually stay in small research or clinical communities. Research is rarely accessible and researchers have few incentives to communicate findings outside of their scientific channels.
Popular media is typically superficial and often primarily interested in controversy that generates public attention.
2. Challenges understanding the science
Science is complicated and in medicine there are rarely absolute truths. The public, however, might expect clear consensus or have difficulty grasping the precise nuance of the science and its findings.
Evidence shows that vaccines do not cause autism or are the reason for increasing diagnosis rates. But it is also in the nature of science that it can neither verify nor exclude totally that vaccines contribute to autism in single individuals.
They protect against viruses and bacteria that cause significant levels of death and human suffering. Vaccine programmes thus have a good risk-to-benefit ratio but are not perfect.
3. Doubts of science
The public may have doubts about science and scientists. Science often delivers probabilities and models, not absolute truths.
This might be disappointing or misunderstood as being no better than individual attitudes or opinions. Although not true for vaccines and autism, evidence can be contradictory and difficult to replicate, reinforcing public doubts.
This success has made most diseases invisible in many countries today. The absence of these diseases generates implicit beliefs that vaccinations are unnecessary.
5. Vaccines cause immune reaction
To reach the goal of immunisation, vaccines must cause an immune reaction. Therefore, a transient inconvenient physical reaction is a sign of success, and the logic of vaccination.
This alone might be counterintuitive and feed doubts about vaccinations. Compared to other drugs, only the side-effects are experienced, and the main effect is preventive, not immediately experienced.
6. Parallelism of events
Autism is a neurodevelopmental condition commonly appearing in the first years of life. Initial autistic behaviour may coincide by chance with vaccination time points or follow them and mix with immune reactions.
Making a connection between vaccination and the appearance of autism in these cases is inevitable. But correlation is not causation.
7. Drugs in infancy without an emergency
Ethical issues arise when people make decisions for others regarding drugs or feel coerced to take them. This is particularly true for infancy where parents must consent for their babies.
It can feel intuitively wrong to interfere with nature and invasive to give a series of shots to a fragile human being in early development in the absence of a medical emergency.
8. Actual harms from less-well established vaccines
Benefits and risks cannot be generalised across all vaccines. Vaccines that are part of long-standing vaccination programmes have good evidence to back them, indicating a convincing risk-benefit ratio.
New vaccines are not ensured in the same way. For instance, the swine flu vaccine during the 2009 pandemic is suspected of having caused 1300 cases of narcolepsy in Europe.
We must distinguish between well-established vaccines and those developed within a short period. It seems that necessary discussions around the safety of less well-established vaccines affect trust in established ones.
9. Polarised debate of vaccines
Open societies build on trust, freedom of speech and debate – but also on shared responsibility. Recent years have seen a polarisation of views around many topics, including vaccinations, not at least fuelled by the COVID crisis.
The urgency of the situation and need for solidarity left little space and time for discussion in society and marginalised or stigmatised even moderate sceptics. The latter has surely harmed trust in vaccines more generally.
Emerging evidence suggests that lycopene—a natural plant extract—may have antidepressant properties. New research in Food Science & Nutrition reveals the mechanisms behind its antidepressant effects.
Lycopene is a carotenoid, related to beta-carotene and gives some vegetables and fruits (eg, tomatoes, grapefruit) a red colour. Lycopene is a powerful antioxidant that might help protect cells from damage.
In mice with depressive-like behaviours, brain analyses revealed impairments in the hippocampus. Lycopene treatment lessened these impairments and reversed the animals’ depressive-like traits.
Lycopene treatment boosted the expression of brain-derived neurotrophic factor (BDNF), a protein with roles in many aspects of brain function. Experiments indicated that a signalling pathway involving BDNF (called the BDNF-TrkB pathway, which helps regulate learning, memory, and communication between neurons) is inhibited in mice with depression, and that lycopene treatment alleviates this inhibition.
The study “offers an effective avenue for the development of novel antidepressant therapies,” the authors wrote. “We plan to conduct further verification in future studies and include multiple brain regions in our research.”
The South African Health Products Regulatory Authority (SAHPRA) has joined the Medical Device Single Audit Programme (MDSAP), an international audit programme of medicines and medical device regulators aimed at improving efficiencies in the regulation of medical device manufacturers by engaging in work sharing and collaboration. SAHPRA joins MDSAP as an affiliate member, which expands its ability to monitor the manufacturing of medical devices beyond South Africa’s borders.
The MDSAP membership will result in the improved regulation of medical devices and in-vitro diagnostics (IVDs) as it increases SAHPRA regulatory reach and ensures that SAHPRA can leverage the resources of other regulators that participate in the MDSAP to both audit and monitor adherence to quality standards by medical device manufacturers in several countries globally.
“SAHPRA’s admission into MDSAP signals progress in our strategy to ensure the efficient application of our own resources and those of our peers globally in safeguarding the quality, efficacy and safety of medical devices and in-vitro diagnostics (IVDs) used by the South African public,” says Dr Boitumelo Semete-Makokotlela, SAHPRA Chief Executive Officer.
Dr Semete-Makokotlela says that the admission to MDSAP adds to individual agreements for both monitoring and regulatory reliance that SAHPRA already has in place with several regulators the world over, and would thus improve SAHPRA’s quality assurance abilities and has the potential to increase turnaround times in reviewing and approving key medical devices manufactured elsewhere in the world.
