1. A study of the association of breast cancer with duration of oral contracepti

Question

1. A study of the association of breast cancer with duration of oral contraceptive (OC) use compared a group of women with breast cancer to a group of women of similar ages who were admitted to the same hospital for non-cancer diseases. From interviews it was determined who had used OC in the past and for how long. The following data were gathered. If the underlying hypothesis is correct, then there should be an obvious trend in the odds ratios showing a change in risk with increasing years of OC exposure (this is called a "dose-response" relationship) Duration of OC use Never used them

Explanation / Answer

Solution-

Odds ratio calculator assists to compare the chance of an event in a group with another group that is, 2x2 contingency table.

OR = (a/b)/(c/d) or: OR = (a × d)/(b × c)

For 1 Year: OR=0.8289 and 95%CI =from 0.4706 to 1.46

For 1-4 Years: OR= 0.5805 and 95%CI =from 0.3513 to 0.9593

For >4 Years: OR= 0.4304 and 95%CI =from 0.2533 to 0.7313

The trend of OR is decrease.

Lumped together all the OC users and we get,

OR= 0.5788 and 95%CI =from 0.4137 to 0.8098

Conclusion: Here overall OR is less than 1 means that the first breast cancer group was less likely to experience the event.

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