Risk

Risk is the probability that an unwanted event, such as developing a disease, will happen. It can be written as a fraction, a ratio (for example 1 in 100) or a percentage. Risk is usually given over a stated time period.Absolute risk is the actual chance of the event happening in a group.Worked example 1. In a study, 50 out of 10 000 people developed CVD over ten years.risk = 50 ÷ 10 000 = 0.005 = 0.5% (1 in 200)Relative risk compares the risk in a group exposed to a factor with the risk in an unexposed group.relative risk = risk in exposed group ÷ risk in unexposed groupWorked example 2. Over ten years, 30 in 1000 smokers and 10 in 1000 non-smokers had a heart attack.relative risk = (30 ÷ 1000) ÷ (10 ÷ 1000) = 3Smokers were 3 times as likely to have a heart attack. A relative risk of 1 would mean no difference between the groups.A risk factor is anything that increases the probability of developing a disease. Having a risk factor does not mean a person will definitely get the disease, and people without it may still get it.Perceived and actual risk. People's perceived risk, how risky they think something is, often differs from the actual risk. People tend to overestimate rare, dramatic or unfamiliar risks, such as a plane crash, and underestimate common, familiar risks that they feel in control of, such as smoking or a poor diet.