Huge Study Links 99% of Heart Attacks and Strokes with 4 Risk Factors

Data from two countries show that nearly every stroke and cardiac emergency followed a pattern of rising metabolic stress that could have been spotted early.

STORY AT-A-GLANCE

• A large international study found that 99% of heart attacks, strokes, and heart failure cases were preceded by at least one measurable risk factor, meaning these events are rarely random and often develop over years

• High blood pressure was present in more than 93% of people before their cardiovascular event, making it the most common, and powerful warning sign you can monitor and correct early

• Most individuals had two or more risk factors before their first event, showing that elevated blood pressure, blood sugar, imbalanced cholesterol, and smoking exposure stack together to accelerate arterial damage

• Total cholesterol alone does not accurately reflect your true heart risk; markers like HOMA-IR, fasting insulin, triglyceride-to-HDL ratio, and iron levels provide a clearer picture of metabolic stress driving vascular disease

• Addressing root causes — improving insulin sensitivity, eliminating seed oils, building muscle, walking daily and optimizing sunlight exposure — strengthens cellular energy production, and helps protect your arteries long before crisis strikes

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The heart attack that seems to come out of nowhere almost never does. Cardiovascular disease — encompassing heart attacks, strokes, and heart failure — builds silently over years, and the evidence was almost always there, waiting to be noticed. It’s marked by blocked blood flow to your heart or brain and often shows up as chest pressure, shortness of breath, sudden weakness, confusion or collapse. By the time those symptoms appear, damage has usually been building for years beneath the surface.

For decades, a narrative has circulated that many of these events strike people who seemed “perfectly healthy.” That belief shapes how people think about prevention. If catastrophe feels random, there is little motivation to monitor the basics. But large-scale population data tell a very different story.

In 2025, researchers publishing in the Journal of the American College of Cardiology examined long-term health records from massive cohorts in both South Korea and the U.S.^¹ Their analysis focused on what individuals’ health looked like before their first cardiovascular event. Senior author Dr. Philip Greenland of Northwestern University summarized the core finding bluntly, stating that exposure to one or more nonoptimal risk factors before these outcomes was “nearly 100%.”²

Instead of asking whether heart attacks happen without warning, a more accurate question emerges: what patterns were already present in the years leading up to the crisis? The details of that analysis reveal just how consistent those patterns were across populations and age groups.

Nearly Every Heart Attack and Stroke Followed Years of Measurable Red Flags

The Journal of the American College of Cardiology study set out to answer a direct question: Do heart attacks, strokes, and heart failure really occur “out of nowhere”?³ Researchers analyzed 9,341,100 adults in the Korean National Health Insurance Service and 6,803 adults in the U.S.-based Multi-Ethnic Study of Atherosclerosis.

They followed participants for years before their first cardiovascular event and looked back at their prior health data to see whether four conventional risk factors had already crossed above optimal levels.

• Nearly every person had at least one red flag before crisis — Before coronary heart disease events, 99.7% of cases in Korea and 99.6% in the U.S. had at least one nonoptimal risk factor on record, defined in the study as elevated blood pressure (at or above 120/80 mm Hg or on treatment), total cholesterol at or above 200 mg/dL or on lipid-lowering therapy, fasting glucose at or above 100 mg/dL or treated diabetes, or past or current smoking.

  The pattern stayed the same for heart failure and stroke, with more than 99% of people showing prior exposure in both countries. When you hear “99%,” that’s not statistical noise. That means almost no one reached that hospital bed without measurable warning.

• Most people had multiple risk factors, not just one — Between 93.2% and 97.2% of individuals had two or more of these risk factors before their event. That matters to you because risk stacks. One elevated number stresses your system. Two or three accelerate damage at a much faster pace.

  The prevalence of at least one nonoptimal factor exceeded 99% across men and women in nearly every age group. Even in women under 60 — the group with the lowest proportion — more than 95% of heart failure and stroke cases had existing risk factors. That eliminates the illusion that youth or gender offers protection if numbers drift upward.

• Blood pressure dominated the field — Among all variables, high blood pressure stood out as the most common risk. In both countries, more than 93% of people who later had a heart attack, stroke or heart failure had high blood pressure beforehand. That means their artery walls had been absorbing excess force with every heartbeat — thousands of times per day — long before the emergency.

• Smoking multiplies injury and clot risk — Tobacco exposure injures vessel walls and increases blood clot formation. A clot that forms on top of unstable plaque blocks blood flow abruptly. That blockage starves heart muscle or brain tissue of oxygen. Cells die within minutes.

• Primordial prevention was emphasized — The findings highlight the importance of preventing risk factors from developing in the first place. That phrase, primordial prevention, means stopping the risk before it ever crosses into abnormal territory. It’s not just about treating high blood pressure or diabetes after diagnosis.

  It’s about keeping your blood pressure from drifting upward at all, maintaining normal glucose before insulin resistance develops and avoiding the habits that trigger vascular damage in the first place. Instead of waiting for a prescription, primordial prevention focuses on preserving healthy numbers from early adulthood forward.

• Total cholesterol alone tells you very little about true risk — While the featured study used total cholesterol as a gauge of heart risk, it’s not the best indicator. A more accurate picture of cardiovascular risk comes from looking deeper.

  Focus on your Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) score, which reflects insulin resistance; your fasting insulin and fasting blood sugar levels; your HDL-to-total cholesterol ratio; your triglyceride-to-HDL ratio; and your iron level, since excess iron drives oxidative stress inside arteries.

  When your cells stop responding to insulin efficiently, glucose lingers in your bloodstream longer, and your pancreas pumps out more insulin to compensate. That excess insulin promotes inflammation, stiffens artery walls, and accelerates plaque formation. These markers show how your body handles glucose and fat, which gives you a clearer assessment of real-world risk than total cholesterol alone.

Control the Drivers of Heart Disease Before They Control You

Almost every cardiovascular crisis in the data followed years of abnormal readings. That tells you something powerful. The root cause isn’t random fate. It’s chronic metabolic stress — rising blood pressure, unstable blood sugar, dysfunctional lipid markers, and toxic exposure from smoking.

When those factors stay elevated, your arteries stiffen, inflame, and narrow. When you correct them, you shift your future. This is actually good news. If 99% of these events follow a predictable pattern, then you have a window — potentially years — to change the outcome. The solution lies in restoring metabolic health and cellular energy so your blood vessels stay resilient instead of fragile. Here are five direct steps you can take:

1. Track the right markers — not just total cholesterol — The study’s strength lies in demonstrating that cardiovascular events are almost never random — not in proving that these four markers are the best ones to track. The pattern holds: measurable dysfunction precedes crisis. The question is which measurements give you the earliest and most accurate warning.

   Don’t rely on total cholesterol alone. That combined number tells you very little about your true risk. Instead, monitor your systolic and diastolic blood pressure, fasting blood sugar, fasting insulin, and calculate your HOMA-IR score — details below — to assess insulin resistance. Add your HDL-to-total cholesterol ratio, triglyceride-to-HDL ratio, and iron level. These markers show whether your metabolism is stable or under stress.

2. Restore metabolic health with targeted carbohydrates, not carb restriction — Chronic carb restriction impairs mitochondrial energy production and drives stress hormones. Mitochondria are the power generators inside every cell, including the cells lining your blood vessels. When they falter, those vessel walls can’t repair themselves or relax properly. Most adults thrive on 250 grams of carbohydrates daily, more if you’re active.

   Start with easily digested carbs like fruit and white rice, especially if your gut health is compromised. Then, gradually add in root vegetables, non-starchy vegetables, starchy vegetables like squash or sweet potatoes, beans and legumes, and finally minimally processed whole grains — only if your gut can handle them.

3. Eliminate seed oils from your diet — Excess linoleic acid (LA) from industrial seed oils damage mitochondrial function and promote arterial inflammation. LA is a polyunsaturated fat that, in excess, breaks down into toxic byproducts called oxidized lipid metabolites. These damage the inner lining of your arteries and impair mitochondrial function.

   To lower your exposure, eliminate seed oils, including corn, soybean, canola, sunflower, and safflower oils. When dining out, ask for food cooked in butter and avoid most sauces. At home, read ingredient labels — seed oils appear in mayonnaise, salad dressings, crackers, and even “health” foods. Replace seed oils with grass fed butter, ghee or tallow.

   Aim for a daily LA intake below 5 grams and ideally closer to 2 grams. To track your intake, download the upcoming Mercola Health Coach app, which includes the Seed Oil Sleuth feature that calculates LA exposure with precise accuracy.

4. Build muscle and walk daily to normalize blood pressure and glucose — Sitting for most of the day erodes your vascular health, even if the rest of your markers look acceptable. Ideally, walk one hour per day, but work up to this amount gradually if you’re just starting out. Add strength training two times per week to preserve lean mass.

   Muscle tissue absorbs glucose directly from your bloodstream — the more lean mass you carry, the more capacity your body has to clear excess blood sugar without relying heavily on insulin.

   If you’re over 50, this becomes even more important. Track your resting heart rate and blood pressure over time. Movement improves both. Start with 15 to 20 minutes of walking daily and add five minutes per week. For strength training, begin with bodyweight movements — squats, push-ups, rows — before adding external resistance.

5. Optimize sunlight for mitochondrial energy production — Sunlight plays a key role in optimizing your cellular health. It triggers nitric oxide to lower blood pressure, sets your circadian rhythm, and boosts melatonin production in your mitochondria, protecting your heart against oxidative stress. But if your body is full of LA from years of seed oil consumption, your skin burns easily.

   That’s why I recommend limiting direct sun exposure between 10 a.m. and 4 p.m. until you’ve been off seed oils for at least six months. Focus instead on morning and late afternoon light. Once your tissues are free from these unstable fats, you’ll tolerate more sun safely, and your body will thrive on the energy it provides.

6. Test for insulin resistance with HOMA-IR — Recognizing insulin resistance early is essential, as it’s a warning sign for your metabolic health. The HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) test is a valuable diagnostic tool that helps assess insulin resistance through a simple blood test, so you can spot issues early and make necessary lifestyle changes.

   Created in 1985, it calculates the relationship between your fasting glucose and insulin levels to evaluate how effectively your body uses insulin. Unlike other more complex tests, HOMA-IR requires just one fasting blood sample, making it both practical and accessible. The HOMA-IR formula is as follows:

   HOMA-IR = (Fasting Glucose x Fasting Insulin) / 405, where

   • Fasting glucose is measured in mg/dL

   • Fasting insulin is measured in μIU/mL (microinternational units per milliliter)

   • 405 is a constant that normalizes the values

   If you’re using mmol/L for glucose instead of mg/dL, the formula changes slightly:

   HOMA-IR = (Fasting Glucose x Fasting Insulin) / 22.5, where

   • Fasting glucose is measured in mmol/L

   • Fasting insulin is measured in μIU/mL

   • 22.5 is the normalizing factor for this unit of measurement

   Anything below 1.0 is considered a healthy HOMA-IR score. If you’re above that, you’re considered insulin resistant. The higher your values, the greater your insulin resistance. Conversely the lower your HOMA-IR score, the less insulin resistance you have, assuming you are not a Type 1 diabetic who makes no insulin.

   Interestingly, my personal HOMA-IR score stands at a low 0.2. This low score is a testament to my body’s enhanced efficiency in burning fuel, a result of increased glucose availability. By incorporating additional carbohydrates into my diet, I provided my cells with the necessary energy to operate more effectively.

   This improved cellular function has significantly boosted my metabolic health, demonstrating how strategic dietary adjustments lead to better insulin sensitivity and overall metabolic performance.

FAQs About Heart Attacks, Strokes, and Major Risk Factors

Q: Do heart attacks and strokes really happen without warning?

A: Most often, no. Large-scale data published in the Journal of the American College of Cardiology show that 99% of heart attacks, strokes, and heart failure cases were preceded by at least one measurable risk factor. In most cases, people had two or more. These events are rarely random. They usually follow years of rising blood pressure, unstable blood sugar, abnormal lipid markers, or smoking exposure.

Q: What are the major risk factors linked to nearly all cardiovascular events?

A: The study identified elevated blood pressure, high total cholesterol, high fasting blood sugar (or diabetes), and past or current smoking as the four nonoptimal risk factors. Blood pressure was the most common, present in more than 93% of people before their event. When these factors remain elevated, they damage artery walls and increase the likelihood of plaque buildup and clot formation.

Q: Is total cholesterol enough to assess my heart risk?

A: No. Total cholesterol alone doesn’t provide a complete picture. A more accurate assessment includes your HOMA-IR score, fasting insulin, fasting blood sugar, HDL-to-total cholesterol ratio, triglyceride-to-HDL ratio, and iron level. These markers reflect metabolic health and insulin resistance, which are central drivers of vascular damage.

Q: What is HOMA-IR and why does it matter?

A: HOMA-IR calculates how effectively your body uses insulin based on a single fasting blood sample. A score below 1.0 reflects strong insulin sensitivity. Higher scores indicate insulin resistance, which increases your risk for cardiovascular disease. Detecting insulin resistance early allows you to correct metabolic dysfunction before it progresses.

Q: What steps lower my cardiovascular risk at its root?

A: Focus on restoring metabolic health. Track blood pressure, glucose, and insulin markers regularly. Consume adequate carbohydrates to support mitochondrial energy production rather than restricting them chronically. Eliminate seed oils to reduce LA exposure. Build muscle and walk daily to improve glucose handling. Optimize sunlight exposure to support nitric oxide release and cellular energy. These steps target the machinery of the disease itself — not just the numbers on a lab report.

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1. Journal of the American College of Cardiology September 29, 2025

2. Science Alert January 9, 2026

3. Journal of the American College of Cardiology September 29, 2025