99% of Heart Attacks and Strokes Share These 4 Risk Factors
Over 93% of people who had a heart attack in the United States already had at least one of four specific, measurable, and entirely modifiable conditions on record before that event. Not after. Before. The proportion rises to 95% in South Korea’s much larger dataset. And when researchers looked at women under 60, the demographic long considered the least cardiovascular-risk-prone, the number barely moved.
More than 99% of people who went on to suffer a heart attack, stroke, or heart failure already had at least one risk factor above optimal level beforehand, according to a large-scale study led by Northwestern Medicine and Yonsei University in South Korea, which analyzed health records over more than a decade for more than 9 million adults in South Korea and nearly 7,000 people in the U.S. That scale matters. At nine million-plus participants followed across two continents for up to two decades, this is not a study whose findings can be attributed to sampling noise or demographic quirk.
The four heart attack stroke risk factors are specific and familiar: high blood pressure, high cholesterol, elevated blood sugar, and tobacco use, whether past or current. None of them are invisible. All of them are measurable at a standard checkup. The information needed to anticipate and prevent cardiovascular events is available to clinicians far in advance of the event, and prevention efforts have still not closed the gap.
The Study: Design, Scale, and What Made It Different
People participating in the cohorts came from South Korea, where more than 9.3 million people had risk factors measured every year through the national health system, and nearly 7,000 people in the long-running U.S.-based Multi-Ethnic Study of Atherosclerosis also had their numbers recorded regularly. That longitudinal design, where risk factor data were collected consistently over time rather than recalled after a cardiac event, is precisely what sets this study apart from prior research.
Senior author Dr. Philip Greenland, the Harry W. Dingman Professor of Cardiology and professor of preventive medicine at Northwestern University Feinberg School of Medicine, said that some recent studies had suggested the major modifiable risk factors are “often” absent in people who experienced heart attacks and similar cardiac conditions. “We doubted that,” he added, “and suspected that that research was missing previous risk factor exposures that could only be studied in long-term data sources.”
Greenland told STAT News that a crucial distinction exists between what the American Heart Association and other medical groups call “optimal” for good health and “clinical” for treatment. Shorter-term studies often only assessed whether a patient had been clinically diagnosed with hypertension or diabetes. This study assessed whether measurements were above the health-optimal threshold, a lower and more meaningful bar for identifying true cardiovascular risk. The result was a dataset that captured subclinical risk that earlier work had missed.
Across both the Korean and U.S. cohorts, the results were definitive: more than 99% of people who developed coronary heart disease, heart failure, or stroke had at least one nonoptimal risk factor before their event, and over 93% had two or more risk factors.
The findings were published in the Journal of the American College of Cardiology. An accompanying editorial was authored by Dr. Neha Pagidipati, a cardiologist and cardiovascular prevention specialist at the Duke Clinical Research Institute, who argued that the results reinforce how critical it is to manage health risks before they escalate to fatal outcomes.
Risk Factor 1: High Blood Pressure and the Heart Attack Stroke Risk Factors Framework
High blood pressure, or hypertension, was the most common culprit, affecting over 95% of patients in South Korea and more than 93% in the U.S. No other single factor came close in either population. This finding is consistent with what cardiologists have observed for decades, but the scale and consistency of the data across two culturally and dietarily distinct populations strengthens the case considerably.
The AHA’s definition of optimal blood pressure is 120/80 mmHg or lower. The study used that threshold, not the clinical cutoff of 130/80 mmHg used for diagnosing hypertension. That means patients who had blood pressure readings of, say, 125/82 mmHg, readings a physician might not yet treat, were still counted as carrying a nonoptimal risk factor. This explains why the numbers came out so high, and why they are clinically significant.
Previous studies may have missed diagnoses or overlooked risk factor levels that were below the clinical diagnostic threshold, which effectively rendered those patients invisible to researchers looking only at formal diagnoses. According to the American Heart Association, nearly half of all U.S. adults have high blood pressure, making it the single most preventable risk factor for cardiovascular disease.
Hypertension exacts its damage gradually. Chronic elevation of blood pressure leads to left ventricular hypertrophy, the thickening of the heart’s main pumping chamber, which may progress over time to heart failure. That progression can unfold silently over years before any symptom appears.
Risk Factor 2: High Cholesterol
High cholesterol does not cause symptoms. There is no pain, no shortness of breath, no early warning sign that prompts most people to seek care. Cardiovascular damage accumulates quietly, often for years, before any clinical threshold is crossed.
A 2025 report in Preventing Chronic Disease found a 13.7% national increase in the prevalence of self-reported high blood cholesterol among U.S. adults from 2019 to 2023, with 34 states seeing an increase over that same four-year window. Prevalence of screening and awareness varied significantly by sociodemographic characteristics and state.
Cholesterol becomes dangerous through a mechanical process. Cardiovascular disease often begins with the buildup of lipid deposits within blood vessel walls, silently setting the stage for atherosclerosis, the medical term for hardening and narrowing of the arteries caused by plaque buildup: fat, cholesterol, calcium, and other substances that collect along artery walls over time. When a plaque ruptures, it triggers an acute blood clot that can block a coronary artery or a vessel supplying the brain, producing a heart attack or stroke within minutes.
Public health and clinical efforts should consider expanding resources and interventions that effectively promote early detection and raise awareness about the importance of cholesterol management, according to the same report. Most adults should have their cholesterol checked every four to six years, with more frequent testing for those with diabetes, existing heart disease, or a family history of elevated cholesterol.
Risk Factor 3: Elevated Blood Sugar
Prediabetes, a state in which blood glucose is above optimal but below the clinical threshold for a diabetes diagnosis, often goes undetected and untreated for years. Greenland’s team found that earlier research had likely missed this category of risk entirely, because those studies relied on formal clinical diagnoses rather than optimal-level thresholds. Blood sugar above 100 mg/dL, even without a diabetes diagnosis, counted as a nonoptimal risk factor in this study’s framework.
The mechanism is well documented. According to the CDC’s diabetes complications resource, high blood sugar can damage blood vessels and the nerves that control the heart over time. That damage is cumulative and dose-dependent, meaning longer duration and higher glucose levels translate to greater arterial injury. The American Heart Association reports that people living with Type 2 diabetes are more likely to develop and die from cardiovascular diseases compared to those without diabetes. The risk associated with diabetes is not simply additive when combined with hypertension or high cholesterol: the combination multiplies the threat to arterial integrity.
In her accompanying editorial, Duke University cardiologist Neha Pagidipati argues that the results show just how important it is to manage health risks before they lead to serious, potentially fatal outcomes. For readers already managing blood sugar, the study’s evidence reinforces the value of tight glucose control, not merely keeping numbers within the clinical “normal” range, but aiming for levels the AHA would classify as optimal.
Risk Factor 4: Tobacco Use, Past and Present
Greenland and his colleagues selected blood pressure, cholesterol, blood sugar, and tobacco use as the four major cardiovascular risk factors for the study’s framework. Cardiovascular damage from tobacco does not resolve immediately upon quitting. Former smokers carry residual risk that can persist for years, which is why the study counted past smoking, not just current use, as a nonoptimal exposure.
According to the CDC’s tobacco and cardiovascular disease resource, smoking increases the risk for coronary heart disease by two to four times and for stroke by two to four times, compared to non-smokers. Even at very low exposure levels, the risk is real: the CDC also notes that people who smoke fewer than five cigarettes a day can already show early signs of cardiovascular disease.
A smoker who also has high blood pressure or elevated cholesterol faces a multiplicative increase in cardiovascular danger, not an additive one. That interaction effect is part of what makes tobacco so dangerous in combination with the other three risk factors on this list. Nicotine accelerates arterial stiffening, promotes platelet aggregation (the clumping of blood cells that initiates clots), and reduces the ability of blood vessels to dilate when demand increases.
Sex differences in tobacco risk deserve particular attention. A 2020 study published in PMC/European Heart Journal Supplements found that female smokers show a 25% higher risk of developing coronary heart disease than men with the same tobacco exposure. That disparity is not widely known, and it matters for how women assess their own cardiovascular risk profiles.
Why “No Symptoms” Is Not the Same as “No Risk”
More than 95% of women under 60 still had at least one nonoptimal factor before heart failure or stroke, a group researchers had previously assumed to be at the lowest cardiovascular risk. When the researchers raised the bar to clinically elevated levels, the pattern held: at least 90% of patients still had at least one major risk factor before their first cardiac event.
Regular measurement of all four risk factors is the only reliable way to identify nonoptimal levels before they cascade into an acute event. Blood pressure checks at a pharmacy or clinic, a standard lipid panel at your annual physical, and a fasting glucose test are all low-cost, widely available tools that this study’s evidence now makes harder to skip.
Hypertension can be measured in minutes. The 2025 ACC/AHA guidelines identify high blood pressure as the most prevalent and modifiable risk factor for cardiovascular disease and all-cause mortality. That determination was made before this study reinforced it with 9 million additional data points.
For a deeper look at how lifestyle behaviors compound over years to reduce cardiovascular risk, the sleep and exercise connection to heart health offers an evidence-based framework for small, sustainable changes that add up.
The Reframing That Matters
Dr. Philip Greenland summarized the study’s implications directly: “We think the study shows very convincingly that exposure to one or more nonoptimal risk factors before these cardiovascular outcomes is nearly 100%. 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.”
That last phrase matters. There has been growing attention in cardiology to emerging risk markers: inflammation, microbiome composition, genetic variants, and environmental exposures. Each of those areas is scientifically interesting. But the Northwestern study argues, with an unusually large dataset, that the four classical risk factors still explain nearly all cardiovascular events. Novel biomarkers are worth researching. They are not yet a reason to divert clinical attention away from blood pressure, cholesterol, blood sugar, and smoking, which remain the main event.
Pagidipati’s editorial in JACC was titled “Most CVD Events Are Preceded by Traditional Risk Factors: Fair Warning!” That framing is pointed. The warning has been available for decades. The data now confirm, at a scale that is hard to dismiss, that it applies to virtually every patient who walks into an emergency room with a first cardiac event.
Read More: 3 Diet Factors Behind Nearly 6 Million Cardiovascular Deaths
What to Do Now
The study’s headline number, 99%, is striking, but the actionable signal is more specific. Over 93% of people in both cohorts had two or more nonoptimal risk factors before their first cardiac event, which means most people who experience a heart attack are not carrying just one problem. They’re carrying several, and those problems interact.
The four risk factors at the center of this research can all be measured at a standard checkup with no specialized equipment. Blood pressure can be assessed in under two minutes. A fasting lipid panel measures total cholesterol, LDL, HDL, and triglycerides from a single blood draw. A fasting glucose or HbA1c test (hemoglobin A1c, a measure of average blood sugar over three months) adds one more tube. Smoking history is self-reported. That’s the full picture.
If any of those numbers fall above the AHA’s optimal thresholds, including blood pressure above 120/80 mmHg, LDL cholesterol above the optimal range for your age and risk profile, fasting glucose above 100 mg/dL, or any history of tobacco use, that information is clinically significant regardless of whether you feel well today. The appropriate response is a specific conversation with a physician about what level of intervention is warranted: lifestyle modification, medication, or a combination.
Asking your provider to assess your results against the AHA’s optimal targets, not just clinical diagnostic cutoffs, is a straightforward and evidence-supported step you can take at your next visit. The researchers found that readings your doctor has not formally flagged as a clinical diagnosis may still be contributing to long-term cardiovascular risk. That gap between “not yet diagnosed” and “no problem” is precisely where this research lands its most important finding.
Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis, or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.
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