Constipation and cathartics as risk factors of colorectal cancer: a meta-analysis.

Since individual case-control studies have failed to resolve the question whether constipation and use of cathartics represent significant risk factors of colorectal cancer, a meta-analysis was performed. The method by Peto was used to calculate pooled odds ratios of the cancer risk among exposed and unexposed subjects. The analysis of 14 previously published case-control studies revealed statistically significant risks for colorectal cancer associated with both constipation and use of cathartics, the pooled odds ratios and their 95 percent confidence intervals being 1.48 (1.32-1.66) and 1.46 (1.33-1.61), respectively. The increased risk applied similarly to both sexes, it was higher in cancer of the colon than rectum. Since constipation and cathartics are associated with much lower odds ratios than various dietary components, such as fat, meat, alcohol, and low-vegetable or low-residue diets, it appears that their risk reflects the confounding influence of underlying dietary habits.