Feeling breathless while climbing stairs? Harvard doctors say it could be an early warning sign of coronary artery disease that many people miss

Heart disease rarely arrives without warning. The problem is that many of those warnings are subtle, easy to ignore, or mistaken for everyday exhaustion. Coronary artery disease (CAD), the most common form of heart disease, often develops quietly over years before it becomes serious enough to trigger a heart attack or major cardiac event.

According to experts at Harvard Health Publishing, CAD usually begins when fatty deposits, known as plaque, start collecting inside the coronary arteries. These arteries supply oxygen-rich blood to the heart. Over time, plaque narrows the arteries and reduces blood flow, forcing the heart to work harder. In some cases, the plaque can rupture suddenly and block circulation altogether.

The alarming part is that many people feel “mostly fine” while the disease silently progresses in the background. That is why doctors increasingly stress early assessment instead of waiting for dramatic symptoms.

Coronary artery disease does not always begin with crushing chest pain. In fact, many people first notice small changes during ordinary activities.

A person may suddenly feel unusually breathless while climbing stairs. Some experience dizziness after mild exertion. Others develop discomfort in the jaw, shoulders, upper arms, or chest during exercise. Cold sweats during physical activity can also be an early clue.

These signs are often brushed aside as stress, aging, lack of sleep, or poor fitness. But cardiologists warn that recurring symptoms during exertion deserve attention, especially in adults with diabetes, high blood pressure, obesity, smoking history, or elevated cholesterol levels.

Women, in particular, may experience less “classic” symptoms. Instead of severe chest pain, they may notice fatigue, nausea, neck pain, or shortness of breath. This difference has been highlighted repeatedly in research from the NIH.

Doctors say one important question matters: does the symptom appear when the heart is working harder? If yes, it should never be ignored.

Modern heart care no longer depends only on symptoms. Doctors now use risk prediction tools to estimate the likelihood of developing cardiovascular disease over the next 10 years.

These calculators usually consider:

Age
Blood pressure
Cholesterol levels
Diabetes status
Smoking history
Family history
Weight and lifestyle habits
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Among the most widely used tools are the ASCVD Risk Estimator developed by the American Heart Association and the American College of Cardiology.

The purpose of these assessments is not to scare people. Instead, they help identify hidden risk before symptoms appear. Someone with no chest pain may still have a high cardiovascular risk because of uncontrolled blood pressure, smoking, or long-term diabetes.

A large government-supported study from the Centers for Disease Control and Prevention (CDC) notes that coronary artery disease remains one of the leading causes of death globally, despite advances in treatment. Much of that burden is linked to late diagnosis and untreated risk factors.

One of the more advanced ways doctors assess hidden CAD risk is through a coronary artery calcium scan, commonly called a CAC scan.

This imaging test looks for calcium deposits inside the coronary arteries. Calcium buildup suggests that plaque has been sitting in the arteries long enough to harden. The higher the calcium score, the greater the chance of blocked arteries and future heart complications.

A CAC score of zero is generally reassuring. But any score above zero means plaque is already present.

Doctors may also order a blood test for lipoprotein(a), or Lp(a), which is increasingly recognised as a strong genetic risk factor for heart disease. People with high Lp(a) levels can develop artery disease even when they otherwise appear healthy.

Research supported by the National Institutes of Health (NIH) has shown that elevated Lp(a) significantly increases the likelihood of cardiovascular disease, especially when combined with other risk factors.

These tests are especially useful because coronary artery disease often progresses silently. A person may look healthy externally while important changes are taking place inside the arteries.

When symptoms strongly suggest CAD, doctors move toward more detailed heart evaluations.

One common test is an electrocardiogram (ECG), which records the heart’s electrical activity. It helps detect rhythm problems or signs of reduced blood supply to the heart muscle.

Stress testing is another major diagnostic tool. During this test, patients walk on a treadmill while doctors monitor heart rate, breathing, blood pressure, and ECG changes. If symptoms or abnormal readings appear during exertion, it may suggest reduced blood flow in the coronary arteries.

In some cases, doctors may recommend:
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Echocardiography
CT coronary angiography
Nuclear imaging tests
Cardiac catheterisation
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These tests help determine how severe the blockage is and whether procedures such as angioplasty or bypass surgery may be necessary.

Experts say testing is not only about diagnosis. It also creates a baseline for future comparison. Even a normal ECG today can become valuable if symptoms appear later.

One of the strongest messages from heart specialists is that coronary artery disease is not a sudden illness. It develops gradually over years, often beginning in early adulthood.

That means prevention cannot start after symptoms appear.

Doctors increasingly encourage people to think about heart health as a lifelong process rather than an emergency response. Regular movement, controlled blood pressure, healthy sleep, reduced smoking and alcohol intake, stress management, and cholesterol control remain the strongest long-term protections.

There is also growing evidence that loneliness, chronic stress, and poor sleep may indirectly worsen cardiovascular risk by affecting inflammation, blood pressure, and hormone balance.

Heart disease is often described as silent, but in reality, the body usually whispers before it screams. The challenge is learning when those whispers matter.