Smoking, alcohol, and high BMI are among the easiest things to track on a population level study. Smoking introduces large amounts of carcinogens into the body

Smoking, alcohol, and high BMI are among the easiest things to track on a population level study. Smoking introduces large amounts of carcinogens into the body, I would expect these results to hold up even when you drill down to the finest level. Alcohol and high BMI are surely direct factors for many cancers as well, but they may also be correlated to other risk factors that are harder to track on population level studies.