Yanwen’s blog

9/13/2026

Happy Birthday!

Yesterday, someone shared with me the 2024 Lancet Commission report, “Dementia Prevention, Intervention, and Care.”

The report updates the Commission's earlier work from 2017 and 2020 and identifies 14 potentially modifiable risk factors for dementia across the life course.

The headline finding is striking: the Commission estimates that addressing these 14 risk factors could potentially prevent or delay nearly 45% of dementia cases worldwide.

The 14 risk factors include:

Environment

• Air pollution

Health-related

• Untreated vision loss

• Hearing loss

• Depression

• Traumatic brain injury

• High LDL cholesterol

• Diabetes

• Hypertension

• Obesity

Lifestyle-related

• Physical inactivity

• Smoking

• Excessive alcohol consumption

Social and educational

• Less education in early life

• Social isolation

Of course, dementia has many causes, including genetic and other factors that individuals cannot control. The 45% figure is a population-level estimate of potentially modifiable risk, not a guarantee that an individual can prevent dementia by changing these factors.

Some risk factors, such as age and family history, are largely beyond our control. But many others can be influenced, at least to some degree, through medical care, lifestyle, environment, education, and social connection.

What strikes me most about the report is its life-course perspective.

The way we age is not determined only by what we do after we become old. It is influenced by things we do—and things that happen to us—many years, even decades, earlier in life.

That means dementia prevention begins much earlier.

Perhaps the lesson is asking a simpler question:

What can I do today that might help me remain healthier tomorrow?

Stay physically active. Keep learning. Protect our hearing and vision. Don't smoke. Manage blood pressure and cholesterol. Maintain social connections. Wear a helmet when appropriate. Get medical problems treated rather than ignored.

None of these things comes with a guarantee.

But perhaps healthy aging means making good choices, year after year, to give ourselves the best possible chance of a healthy future. So that we have more influence over that journey than we sometimes realize.

9/12/2026

Around China's Teachers' Day, I came across an interesting piece of news from New York City, where I live.

Starting this school year, New York City Public Schools is placing a one-year moratorium on student-facing generative AI for students from 2-K through eighth grade. At the same time, the city is putting limits on individual screen time for younger students.

The policy takes a different approach with high school students. The city will require AI-literacy instruction and allow limited, supervised use of several approved AI programs. Every high school student will receive two 45-minute AI-literacy modules covering topics such as how AI works, bias, privacy, risks, and appropriate use.

Teachers can still use approved AI tools for lesson planning and operational tasks, but AI cannot be used for grading, behavior monitoring, or decisions about students' placement, promotion, or graduation.

The policy also prohibits AI companion chatbots across all grades and limits individual screen use for younger students. Students in grades 2-K through second grade will have no one-to-one screen time, while the city recommends no more than 30 minutes a day for grades 3–5 and 45 minutes for grades 6–8. There are exceptions for assistive technology and other necessary uses.

This made me think about a much more fundamental question:

What do children actually need from school?

If AI can answer almost any question a child asks, why do children still need teachers?

Because education is not simply the transfer of information.

A child can ask ChatGPT to explain fractions. AI may provide an accurate explanation in seconds. But an elementary-school teacher can notice that the child is frustrated. The teacher can encourage the child to try again, discover exactly where the confusion lies, adjust the explanation, and perhaps teach the child something that has nothing to do with fractions:

Don't give up just because you don't understand something yet.

AI can answer questions. A teacher can help a child become someone who knows how to find an answer, how to keep trying when the answer doesn't come easily, and how to learn from mistakes.

That distinction matters particularly for young children.

At the elementary-school age, children are still developing their confidence, curiosity, habits, and attitudes toward learning. They are learning not only what to know, but also how to think, how to ask questions, how to work with others, and how to deal with difficulty and frustration.

This is why people have always thought elementary-school teachers have a particularly important role. They are helping children form their first ideas about themselves as learners:

Am I good at learning? Is it safe to ask questions? What happens when I make a mistake? Can I solve something difficult? Do I give up when I don't know the answer?

The NYC policy explicitly puts some of these ideas at the center of its approach. For younger students, the schools say learning should emphasize human interaction, play, discussion, creativity, and the opportunity to work through difficult problems themselves rather than simply outsourcing those problems to a machine.

I find that particularly interesting.

AI may become one of the most powerful tools children will ever have. Before giving children powerful tools, we should make sure they have developed the ability to think for themselves.

They need to experience the frustration of not knowing the answer.

They need to struggle with a difficult problem instead of immediately asking a machine to solve it.

They need to learn how to work with another person, listen to a different point of view, make mistakes, and try again.

And they need to experience something AI cannot provide: a human being who knows them, notices them, encourages them, and believes in them.

The more important question is:

What should children learn to do for themselves before AI starts doing it for them?

9/11/2026

I recently read a disturbing article about medical errors.

A 2016 Johns Hopkins article reported on a study by patient-safety researchers who estimated that more than 250,000 deaths per year in the United States might be associated with medical errors. The researchers arrived at an estimate of 251,454 deaths by analyzing four earlier studies of deaths associated with medical care and extrapolating their findings to U.S. hospitalization data from 2013.

The researchers argued that medical errors were not adequately captured in official U.S. mortality statistics because death certificates generally do not have a separate category for medical error. They suggested that medical errors could therefore rank among the leading causes of death.

Importantly, the article does not portray medical errors simply as individual doctors being careless or incompetent. The researchers emphasized systemic problems, including poorly coordinated care, fragmented healthcare systems, inadequate safety nets, and variations in medical practice.

The key message is:

Medical harm may be undercounted in official statistics, and improving patient safety requires improving healthcare systems. Patients can be harmed by failures in the healthcare system even when nobody intends to cause harm.

What does this mean for ordinary people?

I see several practical lessons.

1. Don't be a passive patient.

Actively participate in your own care.

If a doctor recommends a test, procedure, or medication, it is reasonable to ask:

• What exactly is this test looking for?

• What are the alternatives?

• What are the benefits and risks?

• What happens if I don't do it?

• When will I get the results?

• Who will follow up with me?

A good doctor should not be offended by reasonable questions.

2. Keep your own medical records.

This may be one of the simplest things an ordinary person can do.

Know your medications, allergies, major diagnoses, previous surgeries, test results, and important family medical history. Don't assume that every doctor you see has the complete picture.

This becomes especially important when you see multiple specialists.

3. Don't assume that “someone will follow up.”

This may be one of the most practical lessons.

Have knowledge of your test results. If you have an abnormal test, biopsy, scan, or blood test, know what happens next and when. If you haven't heard anything by the expected time, call.

A test being performed is not the same as the result being reviewed and acted upon.

4. Bring another person when something important is happening.

For a major diagnosis, surgery, complicated treatment, or difficult medical conversation, having another person with you can be extremely helpful.

Two people may remember more than one, and a second person may think of a question you didn't think to ask.

5. Make sure everyone has your current medication list.

Medication errors are one area where patients can sometimes provide an additional layer of safety.

Keep an updated list of your medications, including dosages, and bring it to appointments when appropriate. For a new doctor or a hospital admission, having the actual medication bottles can also be helpful.

6. Speak up when something doesn't make sense.

If one clinician tells you something that seems inconsistent with what another clinician has told you, don't simply assume that someone else will resolve the discrepancy. Ask:

“These two things don't seem to match. Can you help me understand which one is correct?”

It is being an engaged patient.

Finally, healthcare is a team activity, and the patient is a member of the team.

Doctors bring medical knowledge. Nurses, pharmacists, technicians, and other healthcare professionals bring their own expertise. But patients bring something no one else has: knowledge of their own body, history, symptoms, medications, and what has happened to them.

Ask questions. Keep records. Follow up. Speak up when something doesn't seem right.

You don't have to be a doctor to be a safer patient.

9/10/1026

Today is Teachers' Day in China.

I think we sometimes idealize the teaching profession. We like to believe that a child may forget individual lessons, homework assignments, or test scores, but remember the teacher who encouraged him when he was struggling, noticed that he was shy, praised his curiosity, or treated him with unusual kindness. In reality, that teacher rarely exists.

There is certainly a bit truth in that. Teachers don't just teach subjects. They can leave lasting impressions on the children they teach.

This may be especially true of elementary-school teachers, who play a very different role from college professors. An elementary-school teacher is not only teaching reading, mathematics, or science. Ideally, he or she is also helping a child discover how to learn and how to see himself as a learner.

At that age, children are still forming some very basic beliefs:

Am I good at learning? Is school a place where I belong? What happens when I make a mistake?
Do adults believe in me? Am I capable of doing difficult things?

A teacher's positive response to these questions can stay with a child for years.

Someone once asked me to name a teacher I still remember decades later—someone who had a far-reaching impact on my life.

Sadly, I couldn't name one.

That made me wonder: How many of us can actually remember our elementary-school teachers, decades after leaving their classrooms?

Perhaps not as many as we might expect. I'm not even sure how many of my children's elementary-school teachers they still remember today.

This makes me think differently about Teachers' Day.

Teachers certainly deserve appreciation. But I wonder whether we sometimes give teachers too much credit for shaping a child's life while overlooking the people who are there long before school begins and long after the school day ends.

A child's first teacher is usually a parent.

Parents teach not through formal lessons, but through everyday life: how to treat other people, how to respond to difficulty, how to handle mistakes, how to work, how to care, and what it means to be responsible. More importantly, children learn by watching their parents.

A teacher may spend several hours a day with a child for a few years. Parents are usually the child's most constant teachers and role models from the very beginning.

So perhaps Teachers' Day should remind us not only to appreciate teachers, but also to recognize the parents who are doing the teaching every day—without a classroom, a lesson plan, or even realizing that they are teaching.

Before a child ever has a teacher at school, he already has one at home.

9/9/2026

Last year, at my birthday gathering, we learned from the former girlfriend of a young relative that she and her boyfriend had ended their 12-year relationship because he had been seeing another woman. This was not the first time something like this had happened.

Last weekend, I learned that he is planning to visit us over Thanksgiving. I haven't talked to him about what happened last year, but this time I feel that I should.

He is 38 years old, an adult, and ultimately he is responsible for his own decisions and their consequences. So what can I say to him that might actually be useful?

I know what I don't want to say.

I don't want to tell him things he already knows. I don't want to say anything that will immediately put him on the defensive, make him feel judged or guilty, or turn the conversation into a lecture. I don't want to bring up how much his mother suffered and worried when she heard about what happened. That could make him feel emotionally manipulated.

So what can I say? Perhaps I can simply ask:

Why did you do it?

What would you do differently next time?

What was happening inside you that led you to make those choices?

What were you looking for when you were seeing another woman?

Was there something you were unhappy about but unwilling or unable to confront honestly?

Were there problems in the relationship that you didn't know how to deal with?

Twelve years is a long time to share your life with someone. Whatever happened in that relationship is now in the past, and the choices were his to make. But I hope he doesn't see this simply as the end of one relationship and the beginning of another.

I hope he can use this experience as an opportunity to understand himself better.

Most importantly, what part of this experience was about the relationship, and what part was about you?

Because if someone enters a new relationship without understanding what happened in the previous one, there is a risk of repeating the same pattern.

I hope he can arrive at his own conclusions.

A good relationship requires honesty, responsibility, and the courage to face problems directly rather than avoid them. But those are things he has to understand for himself. No lecture from me is going to make that happen.

If I do talk to him, perhaps I can simply ask:

“What do you think you've learned from this experience about yourself?”

Perhaps I should write to him, and then wait... if he ever replies.

A friend commented, “根据我的观察，这种在婚姻和恋爱关系上有三心二意，不忠不诚的行为是改不了的。除非等他有某种缺陷了， 身体、经济、年龄或其他弱化了的原因。

… 你如果真想和他谈谈，可以问问他为什么和前女友分手。 是因为性格不合，还是其他什么原因让他见异思迁。 如果他是没有commitment，就是玩玩而已的那种，那就没救了。 只能等他自己接受教训以后醒悟了。”

Another reader told me, "It's useless to talk to him. He's going to be 40 years old. You can't change anything."