If all of these men were moderate smokers, let us assume that 100 of them would die of lung cancer in that one year If all of them were heavy smokers let us assume that 200 of them would die of lung cancer in any one year. The absolute risk of dying of lung cancer in moderate smokers would be of 100 men per 100,000 men per year. However 10 men per 100,000 per year would have died even if they hadn't smoked. Therefore the attributable risk in relation to moderate smoking is 90 per 100,000 men per year. Risk could also be expressed in a relative way.
Some study designs such as case control studies can only provide a measure of relative risk.
On the other hand they have the advantage of being cheaper than cohort studies, which give measures of absolute risk. Consideration of relative risk on its own can be misleading. It would mean that if you smoked you had twice as high a risk as getting coronary heart disease than if you did not smoke and four times as high a risk of getting bladder cancer than if you did not smoke. It might be misinterpreted to imply that if you smoked your risk of bladder cancer was greater than your risk of coronary heart disease. From a public health stand point some people might jump to the conclusion that smoking contributes to a greater burden of bladder cancer than it does for coronary heart disease.