Heart attacks and strokes rarely occur without warning.
According to health data from more than 9 million adults in South Korea and the US, nearly everyone who develops heart disease and suffers a major cardiovascular event has one of four major risk factors in the lead-up.
These factors include high blood pressure, high cholesterol, high blood sugar levels, and tobacco smoking (past or current).
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Combined as a group, they preceded 99 percent of all cardiovascular events during the long-term study, which was published in 2025.
Even in women under 60 – the demographic with the lowest risk of cardiovascular events – more than 95 percent of heart attacks or strokes were linked to one of these existing risk factors.
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High blood pressure was the factor most commonly tied to cardiovascular events. In both the US and South Korea, more than 93 percent of individuals who experienced a heart attack, stroke, or heart failure had hypertension beforehand.
Managing this risk factor could, therefore, be key to preventing serious cardiovascular disease down the road.
"We think the study shows very convincingly that exposure to one or more nonoptimal risk factors before these cardiovascular outcomes is nearly 100 percent," senior author and cardiologist Philip Greenland from Northwestern University said in September when the research was published.
"The goal now is to work harder on finding ways to control these modifiable risk factors rather than to get off track in pursuing other factors that are not easily treatable and not causal."
Greenland and his co-authors note that their results challenge recent claims that insidious cardiovascular events occurring in the absence of risk factors are increasing, suggesting that previous studies may have missed diagnoses or overlooked risk factor levels that were below the clinical diagnostic threshold.
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In an accompanying editorial, Duke University cardiologist Neha Pagidipati (who was not involved in the study) argues that the results show just how important it is to manage health risks before they lead to serious, potentially fatal outcomes.
"We can – and must – do better," she writes.
The study was published in the Journal of the American College of Cardiology.
An earlier version of this article was published in October 2025.