A non-communicable disease cannot be passed from one person to another, because it is not caused by a pathogen. Many of these diseases are caused by a number of factors that interact, such as genes, lifestyle and the environment. Having one risk factor does not mean a person will definitely get the disease, but several factors together increase the risk.
Cardiovascular diseases affect the heart and blood vessels. Risk factors include smoking, a diet high in fat, lack of exercise and the genes a person inherits. Many forms of cancer also have a number of causes, including smoking and other lifestyle factors.
Some diseases of the lungs and liver are non-communicable. Bronchitis affects the lungs and is linked to smoking and air pollution. Cirrhosis is damage to the liver, and it is linked to drinking too much alcohol.
Some diseases are influenced by nutrition. Type 2 diabetes is more likely in people whose diet is high in sugar and fat, and who become obese and take little exercise.