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How Do We Know What We Know? · Truth in Motion with Dr. Jocelyn

• 0:02
  SPEAKER_00: Welcome to Truth in Motion with Dr.
• 0:05
  SPEAKER_00: Jocelyn, where insight, clarity, and wisdom help you thrive.
• 0:10
  SPEAKER_00: Happy Monday, everyone! Last week, we asked, what makes a question meaningful?
• 0:16
  SPEAKER_00: What science can and can't answer?
• 0:20
  SPEAKER_00: And whether reality is real.
• 0:22
  SPEAKER_00: On Friday, we asked, What exists?
• 0:26
  SPEAKER_00: We started from the one thing none of us can doubt: experience itself, and found a self, an ordered world, minds that fit it, and truth worth seeking.
• 0:38
  SPEAKER_00: And we saw that the scan shows the body, but it doesn't show the person.
• 0:43
  SPEAKER_00: This week we take the next step on the ground we're standing on.
• 0:48
  SPEAKER_00: How do we know what we know?
• 0:52
  SPEAKER_00: On Friday, we met ontology, the study of what is.
• 0:57
  SPEAKER_00: Now we ask the next question.
• 1:00
  SPEAKER_00: Once we say something is real, how do we know it?
• 1:04
  SPEAKER_00: That question has a name too.
• 1:07
  SPEAKER_00: Epistemology.
• 1:09
  SPEAKER_00: It comes from the Greek episteme, meaning knowledge and logos, which means study.
• 1:16
  SPEAKER_00: Epistemology is the study of how we know.
• 1:20
  SPEAKER_00: Today we'll look at why this question matters so much.
• 1:24
  SPEAKER_00: Then we'll lay out a map for the week.
• 1:27
  SPEAKER_00: What's called the ladder of evidence, the kinds of studies medicine uses to know what it knows.
• 1:35
  SPEAKER_00: Each day this week, we'll climb one rung and look closely.
• 1:41
  SPEAKER_00: Why does this matter?
• 1:43
  SPEAKER_00: Because every decision we make about our health rests on something we think we know.
• 1:48
  SPEAKER_00: I know this food is good for me.
• 1:51
  SPEAKER_00: I know this pain is nothing.
• 1:53
  SPEAKER_00: I know that treatment works.
• 1:55
  SPEAKER_00: Each one of those sentences is a claim of knowledge.
• 1:59
  SPEAKER_00: And each one leads to a choice.
• 2:01
  SPEAKER_00: What we eat, whether we see someone, what we put into our bodies.
• 2:07
  SPEAKER_00: I know what many of us really want.
• 2:09
  SPEAKER_00: We want to know how to treat what hurts and how to get better.
• 2:13
  SPEAKER_00: And we are going to get there.
• 2:15
  SPEAKER_00: But every week we're flooded with health information, a new study, a new supplement, a new warning.
• 2:22
  SPEAKER_00: Without a way to sort it, it all sounds equally true.
• 2:26
  SPEAKER_00: So first we're building the foundation.
• 2:29
  SPEAKER_00: Then when you meet the next headline, you'll have the tools to ask, how do we know that?
• 2:35
  SPEAKER_00: And is it true?
• 2:36
  SPEAKER_00: Many of us had walked out of an appointment with one explanation, gone home, read three more online, and heard a fourth from a friend.
• 2:46
  SPEAKER_00: Which one do we trust?
• 2:49
  SPEAKER_00: And why?
• 2:50
  SPEAKER_00: That's epistemology.
• 2:53
  SPEAKER_00: It isn't up in the clouds, it's in the kitchen, the pharmacy, and the exam room every single day.
• 3:00
  SPEAKER_00: In medicine, the main way we come to know is through empirical evidence.
• 3:06
  SPEAKER_00: Empirical means it comes from observation and measurement, not from what sounds right, but from what we can watch happen, count, and check again.
• 3:16
  SPEAKER_00: Two weeks ago, I shared a number with you.
• 3:19
  SPEAKER_00: In a 2019 review of American Cardiology Guidelines, only 8.5% of the recommendations rested on the highest level of evidence.
• 3:32
  SPEAKER_00: Highest level, that phrase means there's a ranking.
• 3:36
  SPEAKER_00: Some kinds of evidence count for more than others.
• 3:39
  SPEAKER_00: Before we look at that ranking, let me take you onto a ship.
• 3:44
  SPEAKER_00: In the spring of 1747, a Scottish naval surgeon named James Lind was serving on a British warship, the HMS Salisbury.
• 3:54
  SPEAKER_00: Scurvy was tearing through the crew, gums swelled and bled, old wounds opened up again.
• 4:01
  SPEAKER_00: Men grew so weak they couldn't stand.
• 4:04
  SPEAKER_00: On long voyages, scurvy killed more sailors than battle did.
• 4:09
  SPEAKER_00: Everyone had a theory.
• 4:11
  SPEAKER_00: Bad air, damp, salt meat, and everyone had a remedy.
• 4:16
  SPEAKER_00: Cider, vinegar, a sulfuric acid tonic, seawater.
• 4:21
  SPEAKER_00: Linda did something unusual.
• 4:24
  SPEAKER_00: On May 20th, he took 12 sailors with scurvy, as alike as he could find.
• 4:30
  SPEAKER_00: Same quarters, same basic diet, and he split them into six pairs.
• 4:35
  SPEAKER_00: Each pair got a different remedy.
• 4:38
  SPEAKER_00: One pair got two oranges and a lemon every day.
• 4:41
  SPEAKER_00: Within six days, one of the citrus sailors were fit for duty.
• 4:47
  SPEAKER_00: The other was soon well enough to nurse the rest.
• 4:50
  SPEAKER_00: The other pairs barely changed.
• 4:52
  SPEAKER_00: What made that work wasn't a new theory.
• 4:56
  SPEAKER_00: It was comparison.
• 4:58
  SPEAKER_00: Lynde didn't ask, do my patients get better?
• 5:01
  SPEAKER_00: He asked, compared to what?
• 5:04
  SPEAKER_00: And here's the hard part.
• 5:06
  SPEAKER_00: Lynn published his results in 1753.
• 5:10
  SPEAKER_00: The British Navy didn't make lemon juice standard for sailors until 1795.
• 5:17
  SPEAKER_00: 42 years.
• 5:19
  SPEAKER_00: The evidence was there, habit and opinion held on.
• 5:24
  SPEAKER_00: Even Lind drifted.
• 5:26
  SPEAKER_00: In years later, he still believed damp sea air was a major cause of scurvy.
• 5:32
  SPEAKER_00: And to make citrus easier to carry at sea, he boiled the juice down into a concentrate called a rob.
• 5:40
  SPEAKER_00: The heat destroyed much of what made it work.
• 5:43
  SPEAKER_00: His own clear results got buried under theory, even in his own mind.
• 5:50
  SPEAKER_00: That's how strong our assumptions are.
• 5:53
  SPEAKER_00: Even the person holding the evidence can lose sight of it.
• 5:57
  SPEAKER_00: So let's take that word, comparison, and carry it up the ladder.
• 6:02
  SPEAKER_00: Each rung adds a fairer way to ask the question, compared to what?
• 6:08
  SPEAKER_00: On each one, we'll ask two questions.
• 6:10
  SPEAKER_00: What can this kind of study tell us and what can't it?
• 6:16
  SPEAKER_00: At the bottom is what experienced people believe.
• 6:20
  SPEAKER_00: In my practice, I've seen this work.
• 6:23
  SPEAKER_00: Most experts agree.
• 6:25
  SPEAKER_00: This matters.
• 6:26
  SPEAKER_00: Clinical experience is real knowledge.
• 6:29
  SPEAKER_00: And it's often where good questions start.
• 6:33
  SPEAKER_00: But on its own, it's the easiest kind of knowing to fool.
• 6:37
  SPEAKER_00: We remember the patients who got better.
• 6:40
  SPEAKER_00: We forget the ones who didn't come back.
• 6:42
  SPEAKER_00: Here's an example many of us have lived.
• 6:45
  SPEAKER_00: For generations, the expert advice for a sore back was bed rest.
• 6:50
  SPEAKER_00: Lie down, stay still, let it heal.
• 6:53
  SPEAKER_00: It made sense, and doctors prescribed bed rest for decades.
• 6:59
  SPEAKER_00: Then researchers checked.
• 7:01
  SPEAKER_00: In 1995, a trial in Helsinki, Finland took 186 workers with sudden low back pain and divided them into three groups.
• 7:11
  SPEAKER_00: One group got two days of bed rest, one group got back exercises, and one was told to simply keep up their ordinary activity as much as the pain allowed.
• 7:23
  SPEAKER_00: The group that kept moving recovered fastest.
• 7:26
  SPEAKER_00: The bed rest group did worst.
• 7:29
  SPEAKER_00: Good intentions, expert advice, and it was wrong because no one had checked.
• 7:39
  SPEAKER_00: One rung up is the case report.
• 7:42
  SPEAKER_00: A clinician sees something unusual, writes it up carefully, and publishes it so others can watch for it.
• 7:50
  SPEAKER_00: Can one case matter?
• 7:52
  SPEAKER_00: In 1961, an Australian obstetrician named William McBride sent a short letter to the medical journal The Lancet.
• 8:02
  SPEAKER_00: He had seen severe birth defects, babies born with missing or shortened limbs, in mothers who had taken a new drug for morning sickness.
• 8:12
  SPEAKER_00: The drug was thalidomide.
• 8:17
  SPEAKER_00: He ended by asking whether anyone else had seen the same thing.
• 8:22
  SPEAKER_00: Around the same time, a German pediatrician, Vinuken Lenz, saw the same pattern.
• 8:29
  SPEAKER_00: By the end of 1961, the drug was being pulled from shelves.
• 8:34
  SPEAKER_00: More than 10,000 children around the world had already been affected.
• 8:39
  SPEAKER_00: That's the power of careful observation.
• 8:42
  SPEAKER_00: A case report can't prove a cause, but it can raise the alarm.
• 8:47
  SPEAKER_00: When several similar cases are gathered and described together, that's called a case series.
• 8:54
  SPEAKER_00: It's stronger than one case, but it still has no comparison group.
• 8:58
  SPEAKER_00: We see who got sick, we don't see who took the same drug and didn't.
• 9:05
  SPEAKER_00: The next rung looks backward.
• 9:08
  SPEAKER_00: It's called a retrospective study.
• 9:10
  SPEAKER_00: And the classic kind is the case control study.
• 9:14
  SPEAKER_00: We start with people who already have a disease and compare them with similar people who don't.
• 9:20
  SPEAKER_00: Then we look back and ask, what was different about them before?
• 9:25
  SPEAKER_00: It's fast and it's good for rare disease.
• 9:29
  SPEAKER_00: But it relies on memory and memory can bend.
• 9:33
  SPEAKER_00: Tomorrow we'll sit in on one of the most famous retrospective studies ever done.
• 9:39
  SPEAKER_00: The next rung follows people forward.
• 9:42
  SPEAKER_00: It's called a prospective study.
• 9:44
  SPEAKER_00: And the classic kind is the cohort study.
• 9:48
  SPEAKER_00: We gather a large group of people before anyone gets sick, record their habits, and follow them for years, even decades to see who develops what.
• 9:59
  SPEAKER_00: It's powerful, but people who choose one habit often differ in other ways too.
• 10:05
  SPEAKER_00: On Wednesday, we'll see what that means.
• 10:09
  SPEAKER_00: Next comes the randomized control trial, often called an RCT.
• 10:15
  SPEAKER_00: Here, researchers don't just watch what people choose.
• 10:19
  SPEAKER_00: They assign the treatment by chance like a coin toss.
• 10:23
  SPEAKER_00: That spreads all the other differences evenly, even the ones nobody thought to measure.
• 10:29
  SPEAKER_00: It's James Lynn's idea made fair.
• 10:32
  SPEAKER_00: Many trials add two more protections: a placebo, a stand-in that looks and feels like the real treatment but leaves out the active part, and blinding.
• 10:44
  SPEAKER_00: So the people being treated and the people measuring results don't know who got what, because hope and expectation are real forces too.
• 10:55
  SPEAKER_00: On Thursday, we'll see how an RCT overturned something many doctors were sure of, and we'll look at what trials actually show about acupuncture, cranial sacral therapy, and nutrition.
• 11:10
  SPEAKER_00: The top rung.
• 11:12
  SPEAKER_00: At the top sits systematic reviews and meta-analysis.
• 11:17
  SPEAKER_00: Instead of trusting one study, researchers gather every study on a question, judge each one's quality, and combine the results.
• 11:27
  SPEAKER_00: One study can be a fluke.
• 11:29
  SPEAKER_00: Twenty studies pointing the same way are much harder to dismiss.
• 11:35
  SPEAKER_00: What the latter can't do.
• 11:37
  SPEAKER_00: So should we only trust the top?
• 11:40
  SPEAKER_00: No, and this matters as much as anything else today.
• 11:43
  SPEAKER_00: First, not every question can be tested with a RCT.
• 11:48
  SPEAKER_00: No one would randomly assign people to smoke for decades.
• 11:52
  SPEAKER_00: Second, sometimes a lower rung is enough.
• 11:56
  SPEAKER_00: No one needed a randomized trial to stop the litamide.
• 12:00
  SPEAKER_00: Third, an RCT tells us what happens to the average person in a group.
• 12:06
  SPEAKER_00: None of us is the average person.
• 12:08
  SPEAKER_00: That's why Sackett's definition from two weeks ago has three parts.
• 12:15
  SPEAKER_00: Looking at the best evidence, the clinician's experience, and the patient's own values.
• 12:22
  SPEAKER_00: And fourth, we don't have an RCT doesn't mean it doesn't work.
• 12:28
  SPEAKER_00: Remember, unknown is not the same as useless.
• 12:32
  SPEAKER_00: And on Friday, we'll ask a question the latter leaves out.
• 12:37
  SPEAKER_00: What about knowledge built from watching patients carefully, generation after generation, for more than 2,000 years?
• 12:45
  SPEAKER_00: Not all empiricism is equal.
• 12:48
  SPEAKER_00: What this means for us.
• 12:50
  SPEAKER_00: So here's what this gives us.
• 12:52
  SPEAKER_00: The next time we read a new study shows, can we ask what kind of study?
• 12:58
  SPEAKER_00: Did someone look back or follow forward?
• 13:01
  SPEAKER_00: Did people choose the treatment or was it assigned by chance?
• 13:05
  SPEAKER_00: Is this one study or many?
• 13:07
  SPEAKER_00: And underneath all of them sits James Lynn's question.
• 13:11
  SPEAKER_00: Compared to what?
• 13:13
  SPEAKER_00: This treatment works means little until we know what it was compared with.
• 13:18
  SPEAKER_00: Better than nothing?
• 13:20
  SPEAKER_00: Better than rest?
• 13:21
  SPEAKER_00: Better than what we already do?
• 13:23
  SPEAKER_00: Better than time, which heals so much on its own?
• 13:27
  SPEAKER_00: That one question, what kind of study is this, changes how we hear every headline.
• 13:34
  SPEAKER_00: And it's the first tool in the kit for becoming wise patients and good practitioners.
• 13:41
  SPEAKER_00: In week one, our practice was to notice.
• 13:44
  SPEAKER_00: Last week we started to question.
• 13:47
  SPEAKER_00: This week we keep questioning and we take our questions one layer deeper.
• 13:52
  SPEAKER_00: Here's today's practice.
• 13:54
  SPEAKER_00: Find one health claim this week: a headline, an ad, a post, something a friend told you, then ask, how do they know that?
• 14:04
  SPEAKER_00: What kind of evidence is behind it?
• 14:06
  SPEAKER_00: If you want to go further, ask the questions from the latter.
• 14:10
  SPEAKER_00: Was this one person's story or many people?
• 14:14
  SPEAKER_00: Did someone look back or follow people forward?
• 14:17
  SPEAKER_00: Did people choose the treatment or was it assigned by chance?
• 14:21
  SPEAKER_00: Is this one study or many pointing the same way?
• 14:26
  SPEAKER_00: You don't need to find the answers yet.
• 14:28
  SPEAKER_00: Just ask the question.
• 14:30
  SPEAKER_00: Asking it is where real knowledge begins.
• 14:35
  SPEAKER_00: Today we stepped into epistemology, the study of how we know.
• 14:40
  SPEAKER_00: We stood on a ship in 1747 where 12 soldiers, six pairs taught medicine to ask compared to what.
• 14:49
  SPEAKER_00: And we laid out the ladder of evidence.
• 14:52
  SPEAKER_00: Evidence and expert opinion, the careful single case, looking back, following forward, and the fair test of a randomized trial.
• 15:03
  SPEAKER_00: And the systematic review at the top.
• 15:06
  SPEAKER_00: We also saw that the lat what the ladder can't do and why the best evidence still has to meet a real person.
• 15:14
  SPEAKER_00: And we saw why it matters.
• 15:16
  SPEAKER_00: Every choice about your health rests on something we think we know.
• 15:21
  SPEAKER_00: Knowing how we know is what lets us choose well for ourselves and for the people we love.
• 15:27
  SPEAKER_00: Tomorrow we climb the first rung in depth, looking back.
• 15:31
  SPEAKER_00: We'll sit with two British researchers in 1950, interviewing patients in 20 London hospitals, and see what a retrospective study can and can't tell us.
• 15:43
  SPEAKER_00: Meet me there.
• 15:47
  SPEAKER_00: Keep the conversation going.
• 15:48
  SPEAKER_00: Find your next steps in notes from a fellow traveler, my blog.