Physical inactivity, unhealthy dietary habits, and other health disparities commonly found in low socioeconomic status (SES) populations may be associated with a higher risk of colorectal cancer incidence in the U.S., according to a study published September 4 in the Journal of the National Cancer Institute.
Behavioral risk factors and obesity are more common in low-SES populations in the U.S. compared to more wealthy populations, and unhealthy lifestyles may account for up to 70% of colorectal cancers. While epidemiological and biological studies have shown that unhealthy lifestyles can lead to colorectal cancer, the reason these lifestyles effect low-SES populations to such a large degree remain unknown.
In order to determine how behavioral risk factors and obesity affect low-SES populations, Chyke A. Doubeni, M.D., M.P.H., of the Department of Family Medicine and Community Health at the University of Pennsylvania Perelman School of Medicine and colleagues looked at data from the National Institutes of Health-AARP Diet and Health Study. They looked at patients enrolled from 1995-1996 from six U.S. states and two metropolitan areas and followed through 2006. The health behaviors of the participants were determined by questionnaires and SES was obtained by self-reported education and census-tract data.
The researchers found that of the 506,488 patients studied, 7,676 developed colorectal cancer during the follow-up period, with the adverse health behaviors explaining between 9%-22% of SES disparities in overall incidence. “This study showed that over one-third of the excess risk of invasive adenocarcinoma of the colon and rectum resulting from low SES could be explained by differences in exposure to behavioral risk factors, particularly in an unhealthy diet,” the authors write, adding that their findings suggest that interventions in low-SES communities could reduce SES disparities in colorectal cancer risk.
In an accompanying editorial, John Z. Ayanian, M.D., M.P.P., of the Department of Health Care Policy at Harvard Medical School and John M. Carethers, M.D., of the Department of Internal Medicine at the University of Michigan write that the study further highlights the relationship between SES and its effect on the risk of colorectal cancer, noting that incidence rates were much higher among the less educated adults and of those living in lower income neighborhoods. They write that the study, “underscores the need for more effective public health strategies to improve nutrition and physical activity in the United States and thereby curb the rising tide of obesity, particularly for those with less education and in disadvantaged communities,” adding that, “such efforts can help to ensure that the steadily declining incidence of colorectal cancer since 1975 accelerates more rapidly over the next decade.”