In another study, the smoking habits of 34,445 male physicians were obtained by mailed questionnaires. Deaths among these physicians over the subsequent years were identified though contact with the office of the Registrar General. The death rates from lung cancer of these physicians classified by smoking habits were :

Standardized Death Rates per 1000 Persons Aged 35 or More per Year
Nonsmokers 0.07
Cigarette Smokers 0.96

a. Name the type of study.

b. Calculate the Relative Risk for smokers as compared to nonsmokers.

c. Interpret the results

Annual Death Rates per 100,000 Persons
Exposure Category Lung Cancer Coronary Heart Disease
Heavy Smokers 166 599
Nonsmokers 7 422

a. Calculate the relative risk from Lung Cancer Mortality for Heavy Smokers compared to non smokers. ( 4 points)

b. Calculate the attributable risk of Lung Cancer from smoking.
c. Interpret the results.

d. Calculate the percent attributable risk of Coronary Heart Disease due to smoking

e. Interpret the results.

a. The type of study in both cases is an observational study.

b. To calculate the relative risk, we use the following formula:

Relative Risk = (Incidence rate in exposed group) / (Incidence rate in unexposed group)

In this case, the incidence rate of lung cancer in cigarette smokers is 0.96 per 1000 persons aged 35 or more per year, and the incidence rate in non-smokers is 0.07 per 1000 persons aged 35 or more per year.

Relative Risk = 0.96 / 0.07 = 13.71

c. The interpretation of the results is that smokers have a 13.71 times higher risk of developing lung cancer compared to non-smokers.

d. To calculate the relative risk from lung cancer mortality for heavy smokers compared to non-smokers, we use the same formula:

Relative Risk = (Incidence rate in exposed group) / (Incidence rate in unexposed group)

In this case, the incidence rate of lung cancer in heavy smokers is 166 per 100,000 persons, and the incidence rate in non-smokers is 7 per 100,000 persons.

Relative Risk = 166 / 7 = 23.71

b. To calculate the attributable risk of lung cancer from smoking, we subtract the incidence rate in non-smokers from the incidence rate in heavy smokers:

Attributable Risk = Incidence rate in exposed group - Incidence rate in unexposed group

Attributable Risk = 166 - 7 = 159

c. The interpretation of the results is that heavy smokers have a 23.71 times higher risk of dying from lung cancer compared to non-smokers. Additionally, 159 cases of lung cancer per 100,000 persons can be attributed to smoking.

d. To calculate the percent attributable risk of coronary heart disease due to smoking, we use the following formula:

Percent Attributable Risk = (Attributable Risk / Incidence rate in population) * 100

In this case, the attributable risk of coronary heart disease due to smoking is 599 - 422 = 177 cases per 100,000 persons.

Percent Attributable Risk = (177 / 599) * 100 = 29.55%

e. The interpretation of the results is that 29.55% of the cases of coronary heart disease in the population can be attributed to smoking.