More than half of all heart attacks and strokes are avoidable, a new global study has found.

The Global Cardiovascular Risk Consortium – an international team, including scientists from six Australian research bodies – found that more than half of cardiovascular diseases worldwide are linked to five factors.

All of these factors are a result of unhealthy lifestyles: Being overweight, high blood pressure, high cholesterol, smoking, and type 2 diabetes.

The study found that high blood pressure is the biggest contributor to heart attacks and strokes.

As for the remaining 45 per cent of global heart disease, it’s a bit of a mystery.

If this sounds familiar …

The association between heart diseases and these five factors has long graduated from a matter of scientific inquiry, to everyday health advice from doctors and health sites.

All of these factors are modifiable, meaning they can be turned around, even type 2 diabetes.

The latest big study sought to formally prove the extent of the connection, and how these risks manifest in different parts of the world.

Or as the researchers described their mission: “The objective of the study was to gain a better understanding of the global distribution, the significance of the individual risk factors and their effects on cardiovascular diseases, and overall mortality in order to derive targeted preventive measures.”

They did this by analysing the health records of more than 1.5 million people from 34 countries, including Australia.

Most overweight, biggest smokers

The health records were drawn from North America, Latin America, western Europe, eastern Europe and Russia, north Africa and the Middle East, sub-Saharan Africa, Asia and Australia.

The researchers found that:

• The highest rates for being overweight were in Latin America
• Europe had the highest blood pressure and highest cholesterol
• The risk factor of smoking was “particularly decisive” in Latin America and eastern Europe
• The rates of diabetes were highest in north Africa and the Middle East.

Deaths from cardiovascular disease have declined over recent decades in high-income countries but increased in low- and middle-income countries.

Overall, when the five risk factors are combined, they amount to 57.2 per cent of women’s cardiovascular risk and to 52.6 per cent of men’s.

Giving up smoking is immediately appreciated by your heart. Photo: Getty

Global cardiovascular disease

In a statement from the University Heart and Vascular Centre of the Medical Centre Hamburg-Eppendorf (UKE), which led the study: Cardiovascular diseases cause about a third of all deaths worldwide.

They often develop “silently over decades”.

Frequently without being recognised, the vascular walls change, giving rise to arteriosclerosis. From this coronary heart disease may occur, “including complications such as heart attacks, acute cardiac death, or strokes”.

Lead author Professor Doctor Stefan Blankenberg, the UKE’s medical director, said: “Our study clearly shows that over half of all heart attacks and strokes are avoidable by checking and treating the classic risk factors.”

He said these results “are of the highest significance for strengthening prevention in this area”.

The big mystery

If modifiable lifestyle factors are implicated in only about 55 per cent of heart diseases, what’s going on with the other 45 per cent?

There is no clear answer. There are plenty of other modifiable factors to consider – and other issues that could prove tricky to treat.

Jaime Miranda is professor and head of School of Public Health at the University of Sydney. He is a co-author of the new paper.

He told The New Daily: “We don’t know. Because there are an unknown number of individual and societal factors at play. There’s a lot of complexity.”

He said issues such as the impact of trauma and mental health on the heart need to be explored.

What are the likely answers?

Alta Schutte is Professor of Cardiovascular Medicine at UNSW Sydney and Professorial Fellow at The George Institute for Global Health.

She is also a co-author of the new study.

Professor Schutte told The New Daily: “In the paper we highlighted that we did not include other risk factors, and it is likely that the rest of the risk is made up of a variety of risk factors that have also been identified.”

These were environmental and exposure-related factors such as physical activity, alcohol consumption, air pollution, climate and noise, educational level, or psychosocial risk factors, including depression, that have an effect on the risk of cardiovascular disease.

Biomarkers and genetic variants most likely would add to the prediction of cardiovascular disease risk.

Professor Schutte said there are “very few studies that have included an extensive set of risk factors, thus harder to do such a massive study that include more risk factors”.

“For now – we need action on those that are well known to us and where we can indeed prevent rather than treat”.

Things that can’t be modified

There are a number of non-modifiable factors that contribute to heart diseases, including age, family history and gender – women are more prone to cardiovascular disease than men.

There are infections that can damage the heart, sometimes fatally.

Professor Jonathan Shaw, deputy director (Clinical and Population Health), Baker Heart and Diabetes Institute, and a co-author of the new study told The New Daily: “Age really is the dominant risk factor. Most cardiovascular events are rare in young people and become increasingly common with ageing.”

He said “we also need to remember that being a modifiable risk factor simply means one that is amenable to change”.

This doesn’t mean that it is 100 per cent due to unhealthy lifestyles in all people. That is, not all modifiable risks arise from poor choices. They can come from the hand you’re dealt with.

“As an example, a small proportion of all the people with diabetes in these studies had type 1 diabetes,” he said.

“This is not a lifestyle disease, but is still modifiable by treatment.”

A curious observation

Apart from BMI, the authors write, “the significance of all risk factors decreases with age”.

For example: “High blood pressure is more damaging to a 40-year-old than an 80-year-old.”

How is this the case?

Professor Schutte said this “is almost a case of ‘the damage has been done’ in the 80-year-old. An 80-year-old person already has stiffened arteries and other age-related deterioration in the organs as a result of many years of high blood pressure (or simply due to age).”

In a young person, an increase in blood pressure will have substantial effects on many organs such as the heart, brain and kidneys because at this stage, the organs will still adapt to compensate for the pressure increase, she said.

“This also rings true to other reports that elevated blood pressure in middle ages have a greater predictive value for dementia than having high blood pressure in older age,” Professor Schutte said.

Age-specific relative risks

Professor Shaw said the significance of risk factors decreasing with age “is frequently observed, but not fully understood. The likelihood is that it is because we describe age-specific relative risks”.

In other words, “the risk of a cardiovascular event in the next few years in a 40-year-old with high blood pressure is compared to the risk of a cardiovascular event in a 40-year-old with normal blood pressure”.

“The risk of a cardiovascular event in a 50-year-old with high blood pressure is compared to the risk of a cardiovascular event in a 50-year-old with normal blood pressure, and so on.”

At younger ages, he said, the comparison group is completely healthy.

As age increases, “the comparison group gets less healthy, so the excess risk associated with high blood pressure lessens”.

He said this is probably because “ageing includes some processes that are also part of high blood pressure, even though the blood pressure itself is normal”.