A study followed 900,000 US adults from 1992 to 2008. At baseline, all participants were screened and determined to be cancer free and their body mass index (BMI) was calculated. Body mass index is a measure of obesity that is calculated using a person’s height and weight. Subjects were separated into the following groups according to their BMI: (a) normal weight, (b) slightly overweight, (c) moderately overweight and (d) greatly overweight. 57,145 deaths from cancer occurred in the population during the follow-up period.
a. What type of study is this?
b. Use the data given above to calculate the cumulative incidence of deaths from cancer among the study population over the follow-up period.
c. What additional information would need to be provided for you to be able to calculate the incidence rate of cancer deaths?
d. The following results were seen for men and women when the heaviest members of the cohort were compared to those with normal weight:
Men: Risk ratio of cancer death = 1.5 95% confidence interval = 1.1-2.1
Women: Risk ratio of cancer death = 1.6 95% confidence interval = 1.4-1.9
i. State in words your interpretation of the risk ratio given for the men.
ii. State in words your interpretation of the 95% confidence interval given for men. (Do not merely use the confidence interval to assess statistical significance.)
e. Are these results confounded by gender?