Hi, I'm Professor Paul Elliot, Chair in Epidemiology and Public Health Medicine. Cardiovascular disease or CVD is an umbrella term for a number of related illnesses that affect the heart and circulatory system. As you have already seen, CVD is the leading cause of death globally, accounting for approximately 31 percent of all global deaths in 2016. Many of which occur prematurely before the age of 70. So what is CVD? The term covers all disorders of the heart and blood vessels, including cerebrovascular disease such as stroke, and Transient ischemic attacks, Coronary heart disease or CHD, and Peripheral artery disease. In terms of overall number of deaths, of these, CHD and stroke are the leading causes of cardiovascular deaths. A common feature of this group of conditions is Atherosclerosis which is where deposits of fat, atheroma, build up on the wall of blood vessels causing stiffening, narrowing, and obstruction. This disrupts blood flow and disease occurs when this interferes with function. Atheroma may also break off from the blood vessel as embolie which can cause blockages elsewhere in the circulatory system. For example, stroke is the clinical presentation of disrupted blood flow to the brain. This may arise as a thrombotic stroke due to a blood clot or an embolism which lodges in one of the cerebral arteries and leads to an infarct causing damage and eventual death of that parts of the brain. Stroke can also occur when there is a bleed in the brain, a hemorrhagic stroke. CHD occurs when the blood flow to the muscle of the heart is impaired. Narrowing or blockage of the coronary arteries can lead to acute coronary syndrome which includes heart attack and unstable angina. Peripheral artery disease occurs when blood flow is disrupted in artery supplying organs other than the heart and the brain. Most commonly this causes symptoms in the legs where people present with pain known as claudication and it may eventually lead to skin ulceration and necrosis. While there are specific types in clinical syndromes associated with CVD, many share a common pathological process, atherosclerosis. Which in turn is linked to raise blood pressure and abnormalities of lipid metabolism. There are well established risk factors for CVD which can be broadly divided into modifiable and fixed. Fixed risk factors include older age, being male, and having a family history of CVD. The main modifiable risk factors, things that people may be able to do something about are smoking, unhealthy diet, low in vegetables and whole grains, and high in fat, salt, and sugar, lack of exercise, raised blood pressure, abnormal lipid profiles, and excessive consumption of alcohol. Exposure to high levels of air pollution has also been associated with CVD. It has been estimated that up to 90 percent of CVD may be preventable through making changes in lifestyle. However, it is important to note that these modifiable risk factors are strongly linked with social determinants of disease and health inequalities. Other diseases are also risk factors for CVD, notably diabetes. It is estimated that adults with diabetes are two to four times more likely to die of heart disease than those without. This is because the excess sugar in the blood caused by diabetes sticks to red blood cells and can damage the vessels carrying blood from the heart accelerating the process of atherosclerosis. Furthermore, diabetes and heart disease share many common risk factors. As you've already heard, CVDs are responsible for more deaths globally each year than any other disease. In the Global Burden of Disease Study in 2016, the estimated death rate for CVD was nearly double that of the next highest group, cancers with 239 deaths per 100,000 compared to a 121 deaths per 100,000 for cancers. It is also a significant cause of morbidity with a 105 years lost to disability per 100,000. Although CVD is responsible for the highest proportion of deaths globally, there are some key regional variations. In this graph, countries are shaded according to the rate of CVD deaths. For example, deaths from CVDs in Russia and other parts of Eastern Europe are higher than everywhere else in the world. I previously mentioned that heart disease is responsible for nearly double the number of deaths as the next leading cause, cancer. However, in Eastern Europe, CVD is responsible for nearly four times as many deaths as cancer. In contrast, CVD was only the third highest cause of death in Sub-Saharan Africa. In parts of Asia, including Japan and Singapore, cancer has caused more deaths than CVD. The type of CVD also varies around the world. In most parts of the world, deaths due to CHD is more common than death due to stroke. The exception is in East Asia where the reverse is true. Stroke deaths are more common than CHD deaths. As the global population ages, CVD will likely remain one of the leading causes of death overall for some time to come. But during the 20th century, rates of death due to CVD rose rapidly in the USA and other western countries before dropping markedly. This came about due to reductions in risk factors such as smoking and better control of blood pressure and blood lipids. But this is not yet happening across the world. We are therefore likely to see some contrasting trends in coming decades comparing CVD internationally unless there is a real strengthening of preventative programs worldwide.
