The worldwide view of cardiovascular disease

The Irish Cardiac Society Annual Scientific Meeting and AGM held recently in Galway heard from Prof Salim Yusuf, Past-President of the World Heart Federation, who delivered the Stokes Lecture 2019 on the topic ‘Tackling the global burden of cardiovascular disease (CVD)’.

Among his many career distinctions, Prof Yusuf holds 35 national and international awards for his research activities and has been inducted into the Royal Society Canadian Medical Hall of Fame and has published more than 1,000 papers in peer-reviewed journals. Much of Prof Yusuf’s work has “changed the way cardiologists practise”, said lecture chair Prof Jim Crowley in his introduction.

Prof Yusuf presented the packed auditorium with an overview of some research in which he has been pivotal in providing an overview of risk factors for CVD worldwide in a diverse range of populations. One of these involved a study on 12,000 cases with 12,000 controls in 33 countries. “We found that 90 per cent of the risks of stroke, both ischaemic and intracerebral haemorrhage, were explainable,” said Prof Yusuf, “but the importance of the risk factors were different. For strokes, hypertension was the number-one factor; for heart attacks, myocardial infarction was number-one.

“For the subtypes of stroke, things like tobacco had very little effect on haemorrhagic stroke, but had a bigger effect on ischaemic strokes, so there were variations, but the general principle was that the majority of the risks of stroke and heart attacks could be explained by what we already knew. This does not mean we should not look for new risk factors, but it does mean that we should act on what we already know.”

Prof Yusuf referred to another study that has been ongoing for 20 years looking at risk factors in various regions of the world involving 28 countries and participants between the ages of 35-to-70 years: “Over the first 10 years, we had 11,000 deaths and 40 per cent of these were from cardiovascular disease,” he said. “Twenty-six per cent were from cancers, 8 per cent were from respiratory disease; nine per cent from injuries; around 8 per cent from infection; and 10 per cent were a hotch-potch of conditions.

“However,” added Prof Yusuf, “if you looked at high-income countries, we found that only 23 per cent died from CVD. In middle-income countries it was 42 per cent, and it was about the same in low-income countries. But if you look at the commonest cause of death in high-income countries, such as Sweden and Canada, you see 55 per cent of deaths were from cancer. In middle-income countries this was 30 per cent, and 15 per cent in low-income countries. We are seeing a transition where, as we are getting the better of CVD, deaths from other conditions are increasing.”

Prof Yusuf explained that “the first transition was from infectious diseases of poverty and under-nutrition to chronic diseases, of which CVD was number-one. We are now seeing a second transition within non-communicable diseases, where cancer is becoming the dominant disease. If you look at the ratio of CVD to cancer deaths, you will see that… in high-income countries, only about 40 per cent of the deaths are from CVD [compared to cancer], in middle-income countries it’s about even, and in low-income countries, there are three times as many deaths from CVD compared to cancer. So to all the young cardiologists – if you want to save lives, go to the low- and middle-income countries because that’s where the challenge is.”

However, surprisingly, CVD risk factors were not greater in low- and middle-income countries, explained Prof Yusuf. “There was no association between risk factor levels and CVD, so a paradox became clear. The reason this is important is that most of the focus in CVD prevention has been, ‘let’s reduce the risk factors and the rest will take care of itself’. This research told us that something else is in play — of course, we should reduce risk factors, but there’s something else in play here, and that is [lack of] access to healthcare.”  

He also used further research to address the risk factors associated with CVD and told the attendees: “If you take all the risk factors, by far the greatest one was hypertension. Around one-in-four CVD events worldwide was due to hypertension. Lipids was number two, and number three was household air pollution – we don’t think about household air pollution as being important, but this might be one of the key differences between rich and poor countries. 

“Tobacco was risk factor number four,” continued Prof Yusuf. “Also poor diet, low education, abdominal obesity, diabetes, low grip-strength, low physical activity… but salt consumption was not even on the radar screen. Processed food was not on the radar screen either – processed food consumption is very low in most countries; it’s really in Western countries that it’s higher and our data does suggest that processed food is bad for you, but the population impact is small.

“So we are legislating on the wrong things, and not legislating on the right things.”