Proportion of colon cancer risk that might be preventable in a cohort of middle-aged US men

Objective: Diet and lifestyle likely play major roles in colon cancer incid ence; however, the proportion of colon cancer risk that might be preventabl e is unknown. Thus, we estimated the proportion of colon cancer risk among men in the prospective Health Professionals Follow-up Study that might be a ttributable to a constellation of modifiable risk factors, and thus might b e preventable. Methods: We included 47,927 men aged 40-75 years in 1986, among whom we con firmed 411 colon cancer cases from 1986 to 1996. Risk factors considered we re obesity, physical inactivity, alcohol consumption, early adulthood cigar ette smoking, red meat consumption, and low intake of folic acid from suppl ements. We calculated a risk score that was the sum across the six risk fac tors of the values of 1 (better exposure) to 5 (worse exposure) correspondi ng to the exposure category. We entered the risk score into a logistic regr ession model and estimated the population attributable risk percent (PAR%) using the method of Bruzzi et al. Results: After adjusting for age and family history of colorectal cancer an d comparing the risk score for the combined six modifiable colon cancer ris k factors at or above the approximate 20th, 10th, or 5th percentiles vs. be low, the PAR% increased from 39% (95% confidence interval (CI) = 23-58%), t o 48% (95% CI = 25-71%), to 55% (95% CI = 27-80%), respectively. Using a se cond method in which we used cut-points consistent with general-good health behaviors for each risk factor, comparing men with at least one risk facto r to men without any risk factors (3.1% of the men), the PAR% was 71% (95% CI = 33-92%). Conclusion: The findings from this analysis suggest that, if all the member s of this cohort of middle-aged US men had a modifiable exposure distributi on comparable to the men with low risk scores, a large proportion of colon cancer risk might be avoidable. Additional study is required to determine w hether making changes in these six risk factors now would reduce the risk o f colorectal neoplasia, or whether the proportion of colon neoplasia that m ight be avoidable would be similar in populations with different characteri stics.