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A hundred years ago most people died from infections and communicable diseases. With improved hygiene, vaccinations and healthcare there are fewer of these. However, non-communicable diseases have become more prominent. We are increasingly realising how many are caused by our modern lifestyle.

Cardiovascular disease is a group of diseases of the heart and blood vessels. One of these is coronary heart disease (CHD).

Coronary heart disease

The heart is a muscular pump. Like all muscles, it needs oxygen for aerobic respiration. The coronary arteries supply blood, and therefore oxygen, to the heart muscle.

The coronary arteries may become blocked by a build-up of fatty material, caused by certain kinds of 'bad' cholesterol. As the fatty material increases, one or more coronary arteries narrow, and can become blocked.

If a blockage builds up, the amount of oxygen reaching the heart muscle is reduced. The person will develop chest pain and, if left untreated, a heart attack will follow. This results in damage to, or the death of the heart muscle.

Pulse and blood pressure

As fatty deposits build up in arteries, it becomes more difficult for the heart to pump the blood around the body. It has to beat harder and faster.

The pulse rate can be measured by feeling the pulse on the inside of the wrist or on the side of the neck. It is counted as beats per minute.

Blood pressure is measured by a special machine which actually measures two pressures inside your blood vessels. The first number is higher because it is the pressure in your blood vessels when your heart is contracting. The second number is lower because it is your blood pressure when your heart is relaxed. A good blood pressure is 120 over 70 mmHg.

Causes of heart disease

It is fairly easy to find the cause of communicable diseases by isolating and identifying the pathogen causing it. Non-communicable diseases often have many causes, known as risk factors. The more risk factors you are exposed to, the more likely you are to develop the disease.

The main risk factors for cardiovascular disease:

• genes (family history of heart disease) - there are six genetic variants associated with CHD
• diet high in fat or salt
• high blood cholesterol
• being overweight or obese
• lack of exercise
• high blood pressure
• smoking

Discovering risk factors - The Framingham study

In 1948 a study into the causes of heart disease began in Framingham in the USA. Ever since, every 2 years researchers record certain measurements for each of the 13,000 people taking part. They included body mass, cholesterol level, blood pressure, and lifestyle factors such as smoking and exercising.

One of the risk factors discovered by the Framingham study was having a high blood cholesterol level. They found a strong correlation between the risk factor, which was cholesterol level, and the outcome, which was death rate. In order to claim that the factor is the cause of the outcome there must also be an explanation of how one could lead to the other.

Smoking and cardiovascular disease

Smoking increases the risk of cardiovascular disease in several ways:

• Smoking damages the lining of the arteries, including the coronary arteries. The damage encourages the build-up of fatty material in the arteries. This can lead to a heart attack or a stroke.
• Inhalation of carbon monoxide in cigarette smoke reduces the amount of oxygen that can be carried by the blood.
• The nicotine in cigarette smoke increases the heart rate, putting strain on the heart.
• Chemicals in cigarette smoke increase the likelihood of the blood clotting, resulting in a heart attack or stroke.