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).
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.
High blood pressure was the risk 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 high blood pressure 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.
This, they add, suggests that previous studies may have missed diagnoses or overlooked risk factor levels that were below the clinical diagnostic threshold.
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," Pagidipati writes.
The findings add to other recent research, which suggested we may be underestimating the role of other causes that contribute to heart attack risks, particularly in younger adults.
In a study published in September 2025, scientists from the Mayo Clinic in the US analyzed 1,474 heart attack events in people aged 65 or younger, recorded between 2003 and 2018 in Olmsted County, Minnesota.
By carefully reviewing medical records and imaging, they identified a primary cause behind each case.
Traditionally, most heart attacks have been blamed on clogged arteries causing atherothrombosis – where blood clots block flow to the heart.
Strikingly, more than half of heart attacks in women were found to have non-atherothrombotic causes.
Atherothrombosis accounted for 75 percent of heart attacks in men, which wasn't surprising. But in women, it was behind 47 percent – less than half. That has major implications for the prevention and treatment of heart attacks.
In women, 34 percent of all heart attack events were attributed to supply/demand mismatch secondary myocardial infarctions (SSDMs) – defined as an imbalance of oxygen supply and demand caused by other stressors on the body, such as anemia or an infection.
Among the other factors significantly contributing to heart attacks were spontaneous coronary artery dissections (SCADs), where tears in artery walls collect blood, and embolisms (blood clots traveling from other areas of the body).
"This research shines a spotlight on heart attack causes that have historically been under-recognized, particularly in women," said cardiologist Claire Raphael when the research was published.
"When the root cause of a heart attack is misunderstood, it can lead to treatments that are less effective – or even harmful.
"Understanding why a heart attack happened is just as important as treating it. It can mean the difference between recovery and recurrence."