Non-communicable diseases cannot be passed from one person to another. Many of them are caused by a number of factors interacting, and lifestyle is one of the most important. Four key lifestyle factors are exercise, diet, alcohol and smoking.
Smoking increases the risk of lung disease such as bronchitis, of many cancers, and of cardiovascular disease. A diet high in fat, sugar and salt, together with too little exercise, leads to obesity. Obesity raises the risk of type 2 diabetes and cardiovascular disease. Drinking a lot of alcohol over many years damages the liver and can cause cirrhosis. It also increases the risk of some cancers.
The incidence of a disease is the number of new cases. It differs from place to place. Locally, rates are often higher in poorer areas where smoking and unhealthy food are more common. Nationally, rates change over time: a fall in smoking has been linked to fewer deaths from heart disease and lung cancer. Globally, type 2 diabetes and cardiovascular disease are more common in richer countries, but they are rising fast in lower income countries as diets and lifestyles change.
To compare places fairly, rates are given as a percentage or per 100 000 people. For example, if 100 people in a town of 2000 have type 2 diabetes, the rate is 5%. A correlation between a lifestyle factor and a disease does not prove that the factor causes it.