Question 1

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. . The following results were seen for men and women when the heaviest members of the cohort (greatly overweight) 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

State in words your interpretation of the risk ratio given for the men.

State in words your interpretation of the risk ratio given for the women.

Are these results confounded by gender?

The authors stated that they controlled for confounding many risk factors using a multivariate analysis. State an alternative method that the authors could have used to control for confounding in the design or analysis.

In addition, name two confounding variables that you think should be controlled using this method.