#66: A big coffee study won't change what I do....

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Bold claims make great headlines; clear evidence makes better habits. We take a hard look at the widely shared study suggesting two to three cups of coffee cut dementia risk by 20 percent and unpack what those numbers really mean for your brain and your daily routine.

First, we break down the Harvard JAMA research: massive cohorts of nurses and physicians, decades of follow-up, and self-reported diet data that carry real strengths and built-in limits. We explore why observational studies can’t prove causation, how confounders like sleep, exercise, and income can bend results, and why tea showing similar benefits while decaf shows none points to caffeine yet refuses a tidy explanation. Then we translate relative risk into absolute terms to show how a big percentage drop can still be a small difference in real life, and we discuss the publication bias that comes from testing many hypotheses and promoting only the eye-catching hits.

Next, we turn to trials where the science gets sharper. The CRAVE study randomized coffee days in healthy adults with continuous heart monitoring and found no rise in atrial abnormalities that lead to atrial fibrillation, though there was a bump in benign PVCs. For those with a history of AF, the DCAF trial offers a surprise: participants who kept drinking coffee had almost half the recurrence rate compared with those who quit, suggesting caffeine didn’t worsen outcomes and might even help. The message for most people is reassuring—coffee isn’t the arrhythmia trigger it’s often made out to be.

Our bottom line is practical and personal. If coffee fits your life and doesn’t wreck your sleep, enjoy one or two cups without expecting miracles. Protect your rest first, because sleep debt is a far clearer risk to cognition than a second espresso is a remedy. Stay curious, ask how a study was designed, and look for consistent results across methods before changing routines. If you learned something helpful, tap follow, share this episode with a friend who loves their morning brew, and leave a quick review to help others find the show.

Transcript

Headlines Claim Coffee Prevents Dementia

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In the past few weeks, headlines have exploded with the new claim. Drinking two to three cups of coffee a day reduces your risk of dementia by twenty percent. Social media has run with it, but is it true? Should we be convinced? Should we all now drink two cups a day? Let's see where the evidence takes us. Thanks so much for listening to Live Long and Well with Dr. Bobby. If you like this episode, please provide a review on Apple or Spotify or wherever you listen. If you want to continue this journey or want to receive my newsletter on practical and scientific ways to improve your health and longevity, please visit me at Dr. Bobby Livelongandwell.com. That's doctor as a dr bobby live long and well dot com. Welcome End of One Nation, my dear listeners to episode number sixty six, two cups of coffee a day. Why a big, important coffee study won't change what I do. With recent headlines shouting that coffee reduces dementia risk, some people are now celebrating their morning latte as brain medicine. But other studies warn that caffeine triggers dangerous heart rhythms like atrial fibrillation. So what's actually true? Does coffee really protect your brain? Or is this just another example of epidemiology being mistaken for causation? And if you drink coffee every day to help your brain, should you worry about your heart? Today we'll look at the actual science from large observational studies to randomized clinical trials to separate hype, myth, and evidence when it comes to coffee and your health. Now, I'm a very practical man. If coffee can prevent dementia, then can't I claim that big expensive barista machine I just bought as a qualified medical expense for my health savings account? Well, the IRS says that health savings account can be used for diagnosis, treatment, and prevention. Well, probably crazy thinking. Since the IRS does also say that HSAs can't be used for gym memberships, health food supplements, for general wellness, or household appliances. Oh well, it was fun thinking about it while it lasted. As my listeners may recall, I did a previous podcast episode on coffee, episode eight. In that episode, I laid out the basic case that coffee is generally a fairly clean drug. It improves alertness, may help exercise performance, and may reduce your appetite some. I also emphasized the main downsides: jitteriness, sensitivity in some people, and especially sleep disruption. I also raised an important unresolved question. Is it the caffeine, the coffee itself, or some other compounds in coffee that matter? This question will come up again on today's discussion. But that episode was before the new coffee study. So let's now look at that. That study showed that two cups of coffee a day reduce your risk of dementia by 20%. Am I convinced? Should you be convinced? If you drink one cup of coffee per day, should you increase it to two? The research was done at Harvard and was published in JAMA, a major and important journal. The researchers looked at two databases, one that collect information for decades on nurses, and another one that similarly collected data on doctors. The study had 131,000 people and followed them for up to 43 years. Now, these were observational studies. They did not randomize folks to coffee or no coffee. And perhaps most importantly, these studies were not designed for coffee analysis. They were designed to look at cancer and heart disease and what lifestyle factors might cause them, like smoking or exercise, use of vitamins. So not originally designed for dementia, and not originally designed for questions about coffee. This is really important, and we'll come back to it. Every two years the researchers asked folks about their diet, and this is what they found. Folks who drank two to three cups of coffee had a 20% lower likelihood of getting dementia than those who did not drink coffee or very little. Now that sounds important to me. Here are a few important other findings. Those who drank tea got similar dementia benefits. Those who drank decaf coffee got no benefit. So should we all try to drink two cups of coffee or tea a day? Since I only drink one cup, as any more affects my sleep, should I say forget the sleep, drink an extra cup of coffee to prevent dementia? Well, not so fast. All studies have strengths and limitations, and before making any life changes, we need to look at them. On the positive side, the study had a large number of folks in it, and observe what happened over decades, also very important. They also observed a dose response relationship where drinking more coffee up to a point led to more benefit than less coffee, also important. But there are many concerns about the study and why you should not necessarily rush to believe the findings. This study, like most nutrition studies, asked the patients to recall what they ate and drank, and those data may not be reliable. What is a cup of coffee? The researchers didn't separate out the size of the cup, whether it was espresso, drip, weak, or strong coffee. These could be very important factors. Like all observational studies, there can be confounders or other factors that might have affected the results, like education, economic status, exercise, sleep, diet, and general health orientation. Coffee drinkers might have had healthier lifestyles. Now we get to the important stuff. Tea drinkers had the same benefit. That's a head scratcher. And we know that tea has less caffeine than coffee. And decaf coffee drinkers did not get the benefit. So it appears that caffeine may be the key factor, but yet we can't explain why tea drinkers benefited just as much. Tea has less caffeine, and many tea drinkers drink herbal or caffeine-free tea. If you want to believe that it's not the caffeine and it is the other stuff in coffee or tea like polyphenols, then the DCAF folks should also have done well, but they didn't. It seems to me that the relevant factor was the caffeine, so I find it tough to ignore the equal tea benefits. Mark Twain famously said, there are three kinds of lies. Lies, damned lies, and statistics. Let's talk about the numbers they reported. It sounds really powerful that coffee drinkers had a 20% lower dementia risk. I want that. After doing their adjustments, the folks not drinking coffee had 300 cases of dementia per 100,000 person years. And the coffee drinkers had 141 cases. That means a difference of 160 cases per 100,000. Now that sounds like a lot, but it's really only a difference of 1.5 cases per thousand people each year. So for every thousand people drinking coffee a year, perhaps, perhaps there might be 1.5 fewer dementia cases. And for the other 998 folks, no benefit. To me, that sheds a new light on the 20% reduction. The 20% is a valid interpretation, but it isn't that many avoided cases of dementia when you do the calculations. I mentioned this study was not designed for questions about coffee. So it was a general database with many variables in it. Here's the problem. Once you have a giant database, everyone wants to play with the data and test all sorts of hypotheses. And here's the rub. Researchers typically only publish the ones that look exciting and don't tell you about all the other analyses that did not have something exciting. The study population doesn't tell you how many other failed analyses they or others did before finding the eye-catching headline. Here's a study that shows us just what can happen when you play with the data. The researchers purposefully did just that, exploring whether red meat increases mortality. And they tested the data 1,200 different ways. What do you think they found? Let me pause for a bit. In one third of those analyses, the researchers found that red meat increased mortality and also that two-thirds of analyses showed it reduced mortality. Now, all of these were legitimate ways to analyze the data. So the many choices that you make in how to analyze the data can greatly impact the results. So should we believe the coffee study knowing this? As the saying goes, if you torture the data long enough, it will tell you what you want. In another classic study called, Is Everything We Eat Associated with Cancer? The authors randomly chose 50 ingredients from a bunch of cookbooks and looked at observational studies that studied these foods. What do you think they found? Almost every randomly selected ingredient was associated with either an increase or decrease in cancer. The conclusion of the study, beware of what nutritional headlines you read. All right, where do I net out on the coffee study? I find it interesting, but with many flaws. And I won't change what I do. I feel reasonably convinced that coffee won't hurt my brain, but I don't see strong enough evidence to increase my one cup a day to two. What will you do? Please let me know. Send me a note. If you haven't signed up for my newsletter, just go to drbobbyevidence.com and do so, and you can then email me directly. Now, let's move from observational studies about coffee to real controlled clinical trials, where typically we can more readily trust the results. So let's explore a few studies about coffee and whether it causes your heart to beat abnormally. Now, early thinking was that caffeine in coffee would stimulate the nervous system, increasing our heart rate, and that might lead to heart rhythm problems like atrial fibrillation or ventricular flip-flops. Studies seemed to support the concern, but those studies were small, not well controlled, and often just anecdotes. Now, let's be clear that atrial fibrillation is worrisome since it increases your risk of stroke five fold and causes hospitalization and death. Doctors often counseled their patients to stop drinking coffee if they had a heart attack or had atrial fibrillation. Some important studies help us now figure this out. In the Crave trial, which stands for coffee in real-time atrial and ventricular ectopy trial, they took a hundred healthy folks. Now, note, these are not people with heart disease. So a hundred healthy folks and randomly sent them a smartphone alert to either have coffee or not have coffee that day. Everyone wore a monitor so the researchers could track heartbeats. What did they find? No increase in atrial abnormalities, which is where atrial fibrillation might happen. But they did observe a 50% increase in PVCs, momentary flip-flops in your heart. Now, these are generally felt not to be worrisome. And the researchers did not see ventricular tachycardia or ventricular fibrillation, the really bad stuff. So this study suggests that for healthy people, coffee won't cause you heart rhythm problems. But what if you have atrial fibrillation already? Can you drink coffee? In the DCAF trial, you've got to love the names they create for studies. Anyhow, they took 200 people who had atrial fibrillation that was successfully converted to normal rhythms. So now they were normal, and they randomized them to either continue or discontinue their daily coffee. Now, it's important to note that even though the doctors restored normal heart rhythm, many patients relapse back into atrial fibrillation. After six months, the rate of April atrial fibrillation was almost half in those that had coffee. Surprisingly, those who stopped coffee had a much higher rate of recurrence. So coffee seemed to reduce the risk of atrial fibrillation coming back. Now, did the coffee really reduce the risk? Well, at a minimum, it seems like it didn't worsen things. So let's wrap up. What did we learn about coffee and dementia? Well, big study, lots of press, but pretty flawed. I don't think the evidence tells us to drink more coffee. But the good news is the coffee did not seem to make dementia more common. I hope you also have gained a sense of why studies that get media attention may not hold up to close scrutiny. It's my hope that little by little you learn some of the questions to ask when you hear about a study with remarkable findings. From the clinical trials, coffee also didn't seem to create problems with heart rhythms. Where do we go from here? If you enjoy your morning coffee, current evidence suggests you can keep drinking it without worrying about your heart rhythm and possibly with some health benefits. Until next time, I hope that you live long and well and do enjoy that cup or two of coffee if you wish. It may not solve the dementia problem, and likely you can't charge your next Starbucks to the IRS. But life is about enjoyment, and coffee may be one of those activities that bring that to you. I know that it does for me. Thanks so much for listening to Live Long and Well with Dr. Bobby. If you like this episode, please provide a review on Apple or Spotify or wherever you listen. If you want to continue this journey or want to receive my newsletter on practical and scientific ways to improve your health and longevity, please visit me at Dr. Bobby Livelongandwell.com. That's doctor as the dr bobby livelongandwell.com.