Almost everyone who suffers a heart attack, stroke or heart failure experiences warning signs years before the event, according to landmark research.

The research, which monitored millions of individuals across two continents, revealed that over 99 percent of patients exhibited at least one significant risk factor long before experiencing their first cardiac event.

However, high blood pressure – also known as hypertension – was by far the most common culprit, affecting more than nine in ten of participants. 

The findings overturn the widespread belief that heart disease can strike ‘out of the blue’, affecting people with no obvious health problems.

In fact, the research suggests that the warning signs are there in almost every case – but often go unrecognised or untreated.

Researchers from Northwestern University in Chicago and Yonsei University in Seoul examined medical data from over 9.3 million South Korean adults and nearly 7,000 Americans.

They tracked participants for a span of up to twenty years, utilizing regular health screenings that assessed blood pressure, cholesterol, glucose levels, and smoking history.

By matching these records with later diagnoses of heart attack, stroke, or heart failure, the scientists were able to identify health issues that were present long before any major incidents occurred.

Almost everyone who suffers a heart attack, stroke or heart failure experiences warning signs years before the event, according to landmark research

Data from the NHS indicate that although the majority of cardiac events still transpire in older adults, hospitalizations for heart attacks among individuals in their 30s and 40s have increased in recent times.

The findings across both populations were remarkable: over 99 percent of participants who eventually developed cardiovascular disease had at least one ‘non-optimal’ risk factor, and over 93 percent had two or more.

Alongside high blood pressure, factors included raised blood sugar or a diabetes diagnosis, high cholesterol and past tobacco use.

Even among younger women, who are typically assumed to be at lower risk, more than 95 per cent had at least one red flag before experiencing stroke or heart failure.

‘These findings show very convincingly that exposure to one or more nonoptimal risk factors before cardiovascular outcomes is nearly 100 per cent,’ said senior author Dr Philip Greenland, professor of cardiology at Northwestern University Feinberg School of Medicine.

‘The goal now is to work harder on controlling these modifiable risk factors, rather than being distracted by other factors that are not easily treated and not causal.’

Cardiovascular disease remains the world’s leading cause of death, killing an estimated 18 million people every year.

In the UK alone, it accounts for a quarter of all deaths. Experts say the new findings underscore the importance of early detection and prevention.

NHS figures show that while most cardiac events still occur in older age, hospital admissions for heart attacks among people in their 30s and 40s have risen in recent years.

Experts say the trend is being driven by obesity, high blood pressure and type 2 diabetes, all increasingly common at younger ages in the UK.

Cardiologists also point to poor diet, lack of exercise and high levels of stress as fuelling a new generation of patients who once would have been considered too young for heart disease.

In the US, heart attacks among adults under 40 have been rising by around two per cent a year, according to the American College of Cardiology.

National survey data show that strokes in adults aged 18 to 44 increased by roughly 15 per cent in the past decade, even as rates in older people declined.

American researchers blame the same culprits seen in the UK: obesity, smoking, poorly controlled blood pressure and cholesterol, and soaring rates of type 2 diabetes in younger age groups.

Doctors warn that younger patients are often overlooked because heart disease is still seen as an ‘older person’s’ problem, meaning opportunities for early intervention are missed.

Raised blood pressure, cholesterol and blood sugar can often be controlled through lifestyle changes such as diet, exercise and stopping smoking, as well as with medication.

The problem, doctors warn, is that many people either don’t know they have these conditions, or fail to keep them under control.

High blood pressure, for example, is sometimes called the ‘silent killer’ because it rarely causes symptoms until it has already damaged the heart or blood vessels.

Lead investigators argue that health services should put greater emphasis on identifying risk factors in middle age, before they cause irreversible harm.

Routine screening, particularly for blood pressure and cholesterol, could help spot problems in people who feel otherwise healthy.

The study, funded by the National Research Foundation of Korea, is published in the Journal of the American College of Cardiology.