In a breast cancer study investigating a possible link between the age at which
ID: 3205059 • Letter: I
Question
In a breast cancer study investigating a possible link between the age at which a woman gave birth to her first child and the risk of getting breast cancer, a woman was considered "exposed" if she gave birth to her first child at age 25 or older In a sample of 5000 women who gave birth to their first child before age 25, 50 developed breast cancer. Of 1500 women who gave birth to their first child at age 25 or older, 30 developed breast cancer. Calculate the relative risk of developing breast cancer among the women in the exposed and unexposed groups. Show your work! What does the relative risk imply in this case, i.e. how do you "make sense" of your calculated relative risk?Explanation / Answer
Hi,
Relative risk, also known as risk ratio is the ratio of the probability of an event occurring (for example, developing a disease, being injured) in an exposed group to the probability of the event occurring in a comparison, non-exposed group.
Here, the exposed group is the women who give birth to their first child at age 25 or older and the 'unexposed group' is the women who give birth to their first child before age 25.
The calculated relative risk = (30/1500)/(50/5000)=2. Since this number is greater than 1. This means that women who give birth to their first child at age 25 or older are twice at risk of getting breast cancer than women who give birth to their first child before age 25.