A new international study has delivered a striking message: almost all cases of coronary heart disease (CHD), heart failure (HF), and stroke occur in people who already have at least one traditional cardiovascular risk factor. This challenges the idea that heart attacks can “strike out of the blue” in otherwise healthy individuals.

The research looked at two massive groups of people: over 9.3 million adults in South Korea through the Korean National Health Insurance Service (KNHIS) and 6,803 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) in the US. 

Scientists tracked four key risk factors — blood pressure, cholesterol, blood sugar, and smoking — to see whether people who developed cardiovascular events had any warning signs beforehand.

The findings were striking. Before a CHD event, more than 99% of participants had at least one nonoptimal risk factor. 

The same pattern held for heart failure and stroke. Even in younger adults under 60, over 95% of women and men who developed HF or stroke had at least one risk factor. And having two or more risk factors was also common, affecting 93% to 97% of those who experienced a cardiovascular event.

“These results show that heart attacks, strokes, and heart failure rarely come out of nowhere,” said the research team. “Most people who experience these events have measurable risk factors years before their diagnosis.”

The study highlights the power of early prevention. Keeping blood pressure, cholesterol, and glucose levels in check, avoiding tobacco, and maintaining a healthy lifestyle could prevent the vast majority of these serious health events. In other words, knowing your numbers and taking action early isn’t just smart — it can be lifesaving.

With these findings, doctors and public health experts hope to stress the importance of primordial prevention — addressing risk factors before they even develop — as a critical step to protecting hearts and brains around the world.