Smoking and Diabetes A study to assess the association of diabetes and smoking compared a group of hospitalized individuals with diabetes (cases) with a group of volunteer individuals without diabetes (controls) who were full-time employees of the same hospital where the cases were identified. The results from this study reported, for the first time in the literature, a strong association between diabetes and smoking.

1. What type of bias may be present? Why do you suspect the presence of the bias you have identifies?
2. The magnitude of this association is likely to be either over- or underestimated. Which do you think is the case, and what makes you think so?

1) THE RECALL BIAS

REPORTING BIAS

2)Overestimated

Explanation:

This is a recall bias Because the people or subjects that have diabetes will be trying to remember when the smoked and so on.

They are more likely to recall past exposures and controls;

Reporting Bias: this is because this study is dependent or relies on the individuals reporting of the exposures which they themselves find to be important or relevant to the Study.

The magnitude of the association maybe Over-Estimated because the hospital controls its employees but they don't control the patients. The Employees may be too busy that they don't even have time to smoke through out the day or they may not even be allowed to smoke While the patients can do as they please, even smoking as much as they want for the most part.

1. Inclusive bias

2. Over-estimated

Explanation:

Inclusive bias involves selecting samples for convenience. This occurs in situations where for instance, the volunteer group is the only group available.

Results including this type of bias, cannot be interpreted to fit into an entire population and should only be limited to the narrowed down demographic range provided by the bias.

The association between diabetes and smoking in this study, is likely to be over-estimated as the employees are guided by rules set by the hospital and are controlled by them. This rule could involve prohibiting smoking at work and while running long shifts, employees may not get breaks to smoke. On the other hand, patients don't get to be controlled by the hospital and are much freer to lead their lives as they deem fit.