Hi everyone,
The link between Tylenol in pregnancy and autism or ADHD has always come from observational studies, which track what mothers took but cannot prove cause. Even in those studies, the link was weak. This week, researchers pooled seven meta-analyses, each one a study that combines many earlier studies, covering more than 3 million people. When they kept only the best-quality evidence, the link shrank sharply and in several analyses nearly disappeared. That is really useful for anyone who has worried about it.
I also found a few other studies I thought were interesting and useful for staying healthy. In about 95,000 adults who wore sleep trackers, more REM sleep was linked to lower risk of 83 diseases, and 6 to 8 hours of sleep marked the lowest risk. Another study found that losing muscle as you age was tied to about 42 percent higher dementia risk. A third found that people whose blood carried a fat pattern linked to eating peanuts had about 11 percent lower diabetes risk, and lower body weight explained most of that link. And in a survey of US teens, TikTok was the app its users most often blamed for lost sleep.
On the podcast, Dr. Anne Marie Fine explains which pollutants build up in the body and the changes at home that cut your exposure.
I am a neurosurgeon, and I built an app to exercise your brain. Nine puzzles cover the nine domains of thinking: memory, language, numbers, space, attention, logic, and planning. New puzzles are generated every day, so there is a fresh set waiting for you every morning. They are fun and a little addictive, and they do not feel like work. They feel like a game. I play mine every morning with my coffee. Three games are free to play every day, with no sign-up.
This Week’s Podcast Spotlight
Episode 73: The Silent Toxin Buildup That Ages Your Brain, with Dr. Anne Marie Fine
Dr. Anne Marie Fine is an environmental medicine physician who has spent about 25 years measuring the metals, plastics, and other pollutants people carry in their bodies. A standard blood panel never checks for them. Early in our conversation I asked her about a study she had sent me before we recorded, from the UK Biobank, a large British health research project. The study used blood proteins from 44,000 people to estimate how old each of 11 organs looked. The age of the brain and the immune system predicted how long people lived better than the age of the heart did. A gene called APOE comes in versions that raise or lower Alzheimer’s risk. Young-looking brains carried the Alzheimer’s risk of two copies of the protective version, APOE2. Old-looking brains carried the risk of the harmful version, APOE4, whatever genes the person actually had. In her words, your blood is telling you more than your genome. Your genes are fixed, but how old your brain looks may be something you can change. The last third of the episode covers practical changes at home that cut the pollutants you take in.
What we got into:
- Your indoor air is probably the worst air you breathe. In one study, researchers ran a home’s gas stove for an hour. Three to four hours later, benzene in the room farthest from the kitchen was above the EPA’s limit for outdoor air.
- Avoidance comes first. Anything you never take in is something you never have to detox out. Dr. Fine now thinks every home should have an air filter and a water filter. She also says to get plastics out of food storage and switch to cleaner makeup.
- Menopause can re-dose you with childhood lead. Anyone born before 1980 carries lead stored in their bones, and as bone is lost after menopause, that lead goes back into the bloodstream.
Want to go further? Dr. Fine teaches a course for the general public called How to Thrive in a Toxic World.
This Week in Health Science
Five studies from this week’s research, and I think you will find a few of them practically useful.
Tylenol in Pregnancy: The Autism and ADHD Link Shrank Toward Zero in the Best Studies of 3 Million People
Acetaminophen, sold as Tylenol, is the standard pain and fever reliever in pregnancy. Whether it raises autism or ADHD risk is a question a lot of expecting parents ask. Researchers in Spain pooled seven meta-analyses, studies that each combine many earlier studies, covering more than 3 million people. With every study thrown in, taking acetaminophen in pregnancy went with about 17 percent higher relative risk of autism in the child and 29 percent higher risk of ADHD. Those are the numbers that make headlines. Then they reran the numbers two stricter ways: once with only the better-done reviews, and once with only the most reliable individual studies. The links shrank sharply, and in several analyses came close to no link at all. A real cause usually holds up in the best studies, and this link did not. The authors blame differences between mothers that studies cannot fully measure, and errors in recording who took the drug. If you are pregnant and have a fever or pain that needs treating, this review supports acetaminophen as a reasonable first choice.
Key finding: With every study included, Tylenol in pregnancy went with 17 percent higher autism risk and 29 percent higher ADHD risk. Using only the higher-quality evidence, both shrank toward zero.
My book, 2mm, is almost here, and the first chapter is free to read right now. It is the story of seven years inside the operating room, where every decision is measured in millimeters and every millimeter matters. If you want to read the first chapter, go to 2mmbook.com.
More REM Sleep Was Linked to Lower Risk of 83 Diseases in 95,559 Adults
Most sleep research relies on how people say they slept. In this study from the UK Biobank, a large British health project, 95,559 adults wore a wrist tracker for a week to estimate their sleep stages. Researchers then checked their hospital records for nearly nine years for any of 1,049 diseases. More REM sleep, the dreaming stage, was linked to lower risk of 83 conditions, and more deep sleep to lower risk of 7. The big caveat is which came first. Parkinson’s, dementia, and heart failure disturb sleep years before diagnosis, so some of the poor sleep may be early disease rather than a cause of it. The sturdier finding is sleep length. For 69 of the 86 conditions where sleep length mattered, the lowest risk was at 6 to 8 hours a night. In 41 cases a sleep-length group had higher risk than people sleeping 6 to 8 hours, and 37 of those were people sleeping under 5 hours. An irregular bedtime and wake time was linked to higher risk of 3 diseases, even after accounting for how long people slept. If your schedule shifts a lot night to night, a steady bedtime and wake time with 6 to 8 hours of actual sleep is the practical move.
Key finding: More REM sleep was linked to lower risk of 83 of 1,049 diseases, and 6 to 8 hours of sleep marked the lowest-risk window for 69 conditions.
Losing Muscle With Age Was Tied to 42 Percent Higher Dementia Risk
Sarcopenia is the age-related loss of muscle mass and strength. This review pooled cohort studies that measured people first and then followed them to see who developed dementia. People with sarcopenia had about 42 percent higher dementia risk, very likely somewhere between 26 and 58 percent. The link with obesity depended on age. Obesity before 65 went with about 9 percent higher dementia risk, and obesity at 65 or older with about 17 percent lower. That second number is easy to misread. Dementia has a long silent phase. People lose appetite, weight, and muscle before anyone names the disease. So in later life, being thinner may be an early sign of dementia, and extra weight is probably not protecting the brain. Early dementia costs people muscle too, so part of the muscle link may work the same way. But muscle is one of the few risk factors here you can actually change. If you are not doing any strength work as you get older, resistance training two to three times a week with enough protein is the direct way to hold on to muscle.
Key finding: Across pooled cohort studies, people with sarcopenia had about a 42 percent higher risk of developing dementia.
Peanut Eaters Get Less Diabetes. Here’s Why.
Peanuts carry an unusual kind of saturated fat, the very long-chain type, which behaves differently from the shorter fats in butter or meat. In a six-month trial, 63 healthy young adults ate peanuts, peanut butter, or a spread made with peanut oil every day. Afterward, 51 fat measures in their blood had shifted. Researchers turned those shifts into a blood fingerprint of peanut eating, then looked for it in a German study that tracked who went on to develop disease. For each step up in that fingerprint, risk of type 2 diabetes was about 11 percent lower. That result was thin, and its likely range came close to no effect. Body weight, measured as body mass index, explained about 89 percent of that link. Heart disease showed no link at all. That makes this mostly a weight story. A small handful of peanuts, about 25 grams, is a reasonable swap for chips or sweets, because peanuts are filling and hard to overeat.
Key finding: People carrying more of the peanut blood-fat fingerprint had about 11 percent lower type 2 diabetes risk, and body mass index explained about 89 percent of that link.
Instagram and TikTok Topped Nearly Every Harm Measured in 472 Teens, With YouTube Several Times Lower
A screen time total treats every app the same. This national survey asked 472 US teens aged 13 to 17 what had happened to them online in the past four weeks, and on which of 20 apps. Violent images reached 9.1 percent of teens using Instagram, versus 1.9 percent of teens using YouTube. Feeling worse about yourself because of other people’s posts ran 16.6 percent on Instagram and 13.4 percent on TikTok, versus 4.1 percent on YouTube. Sleep took the biggest hit: 42.2 percent of teens using TikTok said it was disrupting their sleep, compared with 10.2 percent who named text messaging. This is a one-time snapshot of what teens reported. It cannot show whether the apps caused the harm, or whether teens already prone to it were drawn to those apps. If you have a teenager, ask which apps they use rather than how many hours, and keep the phone out of the bedroom overnight.
Key finding: 42.2 percent of teens using TikTok said the app was disrupting their sleep, and violent imagery reached 9.1 percent of Instagram users versus 1.9 percent of YouTube users.
Stay curious. Stay skeptical. And stay healthy.
Dr Kumar