Now, that of course, has changed. We don’t have the burden of infections, especially in higher-income countries, but what has happened is that we have been self-selected to have a very, very robust immune system.

For most of human history, things like being bitten by some wild animal or having any type of traumatic injury has been a part of routine human life. The way that we’ve always combated that has been with inflammation. When the immune system is activated, it results in inflammation. For example, you get a viral infection and you have a fever. That fever is really as a result of the inflammation that’s being caused by the immune system.

What we’re learning is that inflammation is in fact at the heart of atherosclerosis, which is basically at the heart of all heart disease, stroke, and heart attacks. White blood cells, many of them, are full of cholesterol, and they’ll start depositing. Over time, as these plaques build up, they result in blockages that can lead to heart attacks and strokes.

These very robust immune systems are in some ways like a post–Cold War nuclear arsenal, in which you don’t have that threat anymore, but these weapons are still lying around. That’s why we see all these autoimmune diseases, and also we see such a high prevalence of atherosclerosis.

[In a similar way,] even though our nutrition has changed a lot, adaptive mechanisms that were meant to protect us from starvation have now, in fact, led to the dual epidemics of obesity and diabetes, which are some of the main reasons why heart disease remains the number-one killer of people around the world.

Khazan: I noticed that heart-disease deaths are actually going up in certain parts of the country, in a reversal of course. Do you know why that is?

Warraich: There are two things that are happening. Many of the newest cohort that has entered older age in the United States are much more obese than people in the past. It is resulting in a lot of those people getting older and now dying from heart disease.

The other thing is—if you look at the paradox in heart disease, which is different from diseases such as cancer—for most heart disease, you actually have very, very effective ways of preventing and treating it. We have good medications, but we’re losing the battle for information and trust. Many people just don’t trust doctors when it comes to the prescriptions or the advice they give.

There’s still a lot of suspicion about very common, but very effective medications such as statins. We still have a lot of problems getting the right medications to the right people.

Khazan: You’re saying patients don’t trust doctors enough to take the statins they’re prescribed?

Warraich: [Studies show that even] patients who have already had heart attacks are not taking statins or are not on the appropriate dose of statins. That’s a huge deal.