If you have ever wondered whether heart trouble can appear out of nowhere, new evidence says that is rarely the case. A large analysis from Korea and the United States finds that nearly everyone who later suffers a major cardiovascular event had at least one modifiable risk factor beforehand, even when that value did not qualify as a formal diagnosis. The results challenge the idea that heart disease often hits healthy people without warning. They also point to a simple, powerful goal for everyday health: keep blood pressure, cholesterol, blood sugar, and smoking status in the optimal range, not just outside the danger zone. The study was published Sept. 29 in the Journal of the American College of Cardiology.
What the researchers studied
The Korean National Health Insurance Service dataset provided the backbone of the analysis. It is a population-based resource that covers nearly all adults in South Korea. Investigators evaluated 9,341,100 adults aged 20 and older who completed routine screening in 2009, with measurements that included blood pressure, cholesterol, blood sugar, and smoking history, along with prescription records. Participants were followed for 13.3 years and outcomes were confirmed using hospital and mortality records.
The team also examined the Multi-Ethnic Study of Atherosclerosis in the United States, a community-based cohort of 6,803 adults aged 45 to 84 who were free of known heart disease at the start. MESA participants underwent repeated in-person assessments of blood pressure, cholesterol, blood sugar, and smoking status. Cardiovascular events were adjudicated by physicians, and follow-up extended 17.7 years. Outcomes included heart attacks, strokes, heart failure, and related deaths, providing a high-quality check on the Korean findings.
Risk factors beyond formal diagnoses
The researchers did not limit their focus to diagnosed hypertension, diabetes, or high cholesterol. They also flagged “nonoptimal” values, which are levels above ideal but below common diagnostic cutoffs. Benchmarks came from the American Heart Association’s ideal cardiovascular health targets, which are more stringent than many clinic thresholds. For example, a systolic blood pressure between 120 and 139 mm Hg counted as nonoptimal even without a diagnosis of hypertension. The approach reflects real-world risk, since damage can accumulate before a value crosses the line into disease.
Which outcomes were tracked
Events were analyzed by category to show patterns across different forms of heart and vascular disease. The categories included coronary heart disease, myocardial infarction, stroke, and heart failure, along with a composite measure that captured any of these events. This structure allowed the researchers to see whether certain risk factors were more tied to one outcome than another.
The headline finding: almost everyone had a warning sign
Across both datasets and every event type, over 99 percent of people who experienced a cardiovascular event had at least one nonoptimal risk factor beforehand. In the Korean cohort, the proportion was at least 99.3 percent for stroke, at least 99.4 percent for heart failure, at least 99.7 percent for coronary heart disease, and at least 99.8 percent for myocardial infarction. In MESA, roughly 99.5 to 99.7 percent had at least one nonoptimal factor before an event. These figures held up even when looking at different ages and sexes. The narrative that heart disease frequently appears in people with spotless risk profiles does not match the data.
Which risk factors showed up most
Elevated blood pressure was the most common red flag. Before events, about 95 to 96 percent of affected people in Korea and about 93 to 97 percent in the United States had blood pressure above ideal. Elevated cholesterol was also common, seen in approximately 76 to 85 percent in Korea and about 71 to 78 percent in the United States. Elevated blood sugar showed up frequently, even without diabetes, at about 73 to 78 percent in Korea and roughly 54 to 60 percent in the United States. Smoking, whether current or former, was a widespread contributor, affecting about 48 to 68 percent in Korea and about 54 to 63 percent in the United States. Most people had more than one issue; over 93 percent had at least two nonoptimal factors. In the Korean cohort, only 0.3 percent of those with coronary heart disease had none of the four major factors, and about 43 percent had all four.
Findings stayed strong with tougher cutoffs
The investigators checked their conclusions using stricter thresholds. Even then, 90 to 95 percent still had at least one modifiable factor before an event. Importantly, many people with no clinically high readings still had one or more values that were outside ideal ranges. That nuance matters, because it suggests prevention should start earlier and aim higher than the line for a diagnosis.
What this means for prevention
Cardiovascular events rarely occur in people who maintain ideal levels of blood pressure, cholesterol, and blood sugar, and who do not smoke. That makes prevention about more than avoiding a diagnosis; it is about guarding the optimal zone over time. Lifestyle remains the first line: meals rich in produce, whole grains, lean proteins, and healthy fats, avoidance of tobacco, and limited alcohol. Regular movement helps, even modest daily activity around 30 minutes. Stress management and good sleep support healthier readings, and routine checkups help you track progress and catch drift from ideal.
When treatment is needed
If numbers remain above target despite lifestyle effort, prompt treatment can reduce risk and protect the heart and brain. Medications for blood pressure, cholesterol, or blood sugar may be appropriate, with goals tailored in partnership with a clinician. The emphasis should be on sustainable, long-term habits, not quick fixes that fade by next season. Prevention works best when changes become the new normal.
The bottom line
This study’s message is both sobering and empowering. Almost every major cardiovascular event is preceded by modifiable risk factors, often at levels that many people overlook as not yet a problem. Vigilant monitoring, early lifestyle action, and well-timed medical therapy when needed can shift those numbers back toward ideal. The sooner you aim for optimal, the more protection you are likely to gain.
