A weekly roundup of public health news
Air pollution, lead may spur higher risk of dementia
Being exposed to environmental poisons such as air pollution and lead can harm cognitive health. New research finds people exposed to the contaminants may have higher risks for dementia and problems thinking later in life.
As many as 18% of new dementia cases diagnosed annually in the U.S. — about 90,000 — could be linked to lifetime lead exposure, new findings in Alzheimer’s & Dementia show.
Researchers examined health records of U.S. older adults, finding people with the highest estimated levels of lead in their bones had nearly three times the risk of Alzheimer’s disease and more than twice the risk of any type of dementia. The study looked at bones because they serve as a marker of long-term lead buildup.
As people age and their bones naturally break down, stored lead can be released into their bloodstream and move into organs, including the brain. Many of the older adults in the analysis were born before 1980, when environmental lead levels were higher because of sources such as leaded gasoline and lead-based paint.
The cognitive harms posed by lead can start early on in life. Another new study in Neurology links lead exposure before birth to lower performance on cognitive tests 60 years later. Researchers tested cognitive performance in a group of older adults and compared the results to levels of lead found in baby teeth collected from the seniors when they were young. As teeth form in layers, they can capture exposure during pregnancy and early life.
The study found women who had been exposed to higher lead levels during their second trimester of fetal development had lower cognitive test scores as seniors. Each small increase in lead exposure while in utero was tied to lower thinking and memory scores late in life — equivalent to being three years older.
Cognitive function can also be harmed by unhealthy air, a hazard that more than 130 million Americans are exposed to regularly. A Feb. 17 study in PLOS Medicine found long-term exposure to fine-particle air pollution, also known as PM2.5, can directly raise risks for Alzheimer’s disease.
Older adults who lived in areas with higher levels of PM2.5 were more likely to develop the disease than those in cleaner-air areas. The increase in risk was slightly higher for people who previously had a stroke.
The research followed nearly 28 million older adults from 2000 to 2018, during which about 3 million were diagnosed with Alzheimer’s disease.
Alzheimer’s disease, the most common form of dementia, affects about 57 million people worldwide, and incidence is growing as more people live longer. PM2.5 comes from sources such as vehicle exhaust, power plants, wildfires and other types of burning fuel.
Disenrollment rates surge for Medicare Advantage members
Millions of older adults who are enrolled in Medicare Advantage may lose their coverage as plans leave the market, a Feb. 18 study in the Journal of the American Medical Association estimates.
About 10% of the 34 million beneficiaries enrolled in Medicare Advantage plans will be forced to disenroll from their current plan this year because their plan is ending its contract or no longer serving their county.
Forced disenrollment from the program has been on the rise in recent years, impacting about 1% of users in 2024 and 7% last year. In 12 states, more than 20% of Medicare Advantage users face losing their current plan, the study said. In Vermont, 92% of enrollees are affected.
Possible reasons for the increase in plan exits include changes to payments and risk adjustment, as well as higher-than-expected health care use among Medicare Advantage users.
Beneficiaries facing forced disenrollment in 2026 are more likely to be enrolled in PPOs rather than HMOs, in plans offered by smaller insurance carriers and in plans with lower ratings. They are also more likely to live in rural areas and in counties with lower Medicare Advantage participation.
Medicare Advantage plans, which are used by more than half of Medicare-eligible beneficiaries, are offered through private insurers. While they often come with lower monthly premiums, they generally have restricted provider networks, mandatory preauthorization and high out-of-pocket costs.
‘Forever chemicals’ detected in umbilical cord blood
More than two dozen types of so-called “forever chemicals” can be found in umbilical cord blood, a new study finds, raising concerns over potential risks to prenatal development.
The results, published in Environmental Science & Technology, show that fetuses may be exposed to a wide range of per- and polyfluoroalkyl substances, including perfluorinated chemicals, polyfluorinated chemicals and fluorotelomers, some of which have been linked with risks to human health.
Using a newer testing method that can scan for thousands of chemicals at once, researchers uncovered a broader range of PFAS than traditional testing panels detect.
PFAS are chemicals used in products such as nonstick cookware, stain-resistant fabrics, food packaging and firefighting foams. They are often called “forever chemicals” because they do not break down in the environment or human bodies. Thousands remain in use, and many have not been fully studied for health effects.
Previous research has linked prenatal PFAS exposure to low birth weight, preterm birth, altered immune responses to vaccines, metabolic changes and other developmental concerns.
Other recent public health news of note:
• Breathing in tiny pieces of plastic can harm lungs and possibly raise the risk of diseases such as asthma or lung cancer, according to a recent review in Food Bioscience. Microplastics — small plastic fragments that are smaller than 5 millimeters — can irritate lung tissue, cause inflammation, damage cells and carry toxins into the lungs, researchers said.
• Extreme wildfires are increasingly occurring in multiple countries at the same time, limiting the ability to share crews and equipment across borders and making fires harder to control, according to new research in Science Advances. Scientists found that days with hot, dry and often windy conditions — known as extreme fire weather — have become more synchronized worldwide since 1979. In many regions, the number of the high-risk days that occur at the same time has more than doubled.
• Short bursts of high heat during a key stage of wheat growth could become one of the biggest threats to global harvests in coming decades, according to a recent study in Climatic Change. As climate change worsens, extreme heat during wheat flowering could drive up global losses of the crop 30% by 2050 and 75% by 2090, researchers said. Flowering is the stage when wheat plants set grain, which determines final yield.
The Watch is written by Michele Late, who has more than two decades of experience as a public health journalist.experience as a public health journalist.