 Hello everyone, welcome back to dentistry and more. We have another topic in epidemiology that is attributable risk and population attributable risk. So we had seen in cohort study we are analyzing relative risk. So relative risk was nothing but comparison of incidence among exposed group and incidence among non-exposed group. And we get a relative risk value, suppose if it is 4 we can say that the risk in exposed group is 4 times compared to the non-exposed group. But the attributable risk is a different concept where we are checking the power of that particular causal factor in deciding the outcome. If suppose we have smoking and lung cancer, smoking is our cause and lung cancer is our outcome. The attributable risk will determine the attributable power or contributable power of that particular risk factor. Relative risk was comparing the incidence in exposed and non-exposed group and explaining the risk. So there is a comparison group and that relative risk will be always a number. So it will be like 3, 4, 6, 5.2, 6.3. But the attributable risk we are expressing at an percentage. So the formula is little different that is incidence among exposed minus incidence among non-exposed divided by incidence among exposed into 100. So that is attributable risk of that particular causal factor. So incidence among exposed is a by a plus b. So incidence is a and c, exposed is a plus b and c plus t. So a by a plus b minus c by c plus t divided by a by a plus b. So let's forget about the calculation, this is a concept. So we get 60% so that means the attributable risk or the attributable power of that particular causal factor that is smoking a 60% which means if 100 people have that causal factor, the 60 out of 100 would get the outcome. In other words, if 100 people smokes, 60 people will get lung cancer. So that is the attributable risk of particular causal factor. So this percentage is not there in relative risk. Relative risk is a different concept compared to non-exposed group. The exposed group has this much risk, 5 times risk, 7 times risk or 8 or 9 times risk. This is particularly we are highlighting the attributable risk of a causal factor in percentage. So population attributable risk is a different concept but almost same. The thing is it is applying into a population. The formula is a little different, incidence of total population minus incidence of non-exposed group divided by incidence of total population. So here we are including the incidence of suppose we are taking lung cancer and our causal factor is smoking. So people are there with lung cancer due to many reasons. So not just smoking causes lung cancer, there are other conditions which can result in lung cancer. So we are including all the lung cancer patients with all the causal factors which is minusing from incidence of other reasons that is non-smoking reasons. So what we get? We get only incidence of people with smoking as a causal factor that is incidence of lung cancer with smoking as a causal factor and which is divided by incidence of total population and we get 60 percentage. So that means if we remove that particular causal factor from the population we could prevent the incidence of lung cancer by 60 percentage. In other words if we are stopping smoking of that population we could prevent 100 lung cancers out of 100 we could prevent 60 lung cancers. So only 40 would happen. That is the idea of population attributable risk. This is commonly applied in preventive programs such as smoking cessation programs. First we need to find out the population attributable risk. So if we are applying the preventive strategies, tobacco cessation counseling, this much incidence of lung cancer could be prevented. So here it is 60 percentage. So we could prevent 60 lung cancers. So total if it is 100 we could prevent 60 lung cancers. So that is the concept of population attributable risk. So the change is total population here it is exposed. So total population exposed group that is only change. So it is a concept what is attributable or contributable risk and population attributable risk. I will come up with a new topic in the industry and more. Thank you.