A risk factor is something linked to an increased rate of a disease. Risk factors can be aspects of a person's lifestyle, or substances in the person's body or environment. For some risk factors a causal mechanism has been proven, meaning scientists know how the factor leads to the disease. For others, there is a correlation but the mechanism is not yet proven. Many diseases are caused by the interaction of a number of factors.
Examples to know: a diet high in fat raises blood cholesterol, and smoking and lack of exercise also raise the risk of cardiovascular disease. Obesity is a risk factor for Type 2 diabetes. Alcohol damages the liver and affects brain function. Smoking causes lung disease and lung cancer. Smoking and alcohol during pregnancy harm the unborn baby: smoking can cause a low birth mass, and alcohol can damage the baby's development. Carcinogens, including ionising radiation, are risk factors for cancer because they can cause cancer by damaging genes.
Non-communicable diseases have a human cost and a financial cost. For an individual, they can mean pain, a lower quality of life, and a loss of income. For a local community and a nation, they mean the cost of treatment, medicines and care, and loss of working days. Globally, the rise in these diseases puts strain on health services. Lifestyle changes in a population change the incidence of disease at local, national and global levels.
When you interpret data on risk factors, look for a correlation on a chart, graph or table, and ask whether the sample was large enough and representative.