Inverse Relationship Between Polio Incidence in the US and Colorectal Cancer

Polio is predominantly an enteric viral infection that was progressively eradicated in the United States after the introduction of polio vaccine in the early 1950s. U.S. colorectal cancer rates have dropped steadily for individuals born between 1890 and 1950, but have been increasing for every generation born since 1950. Moreover, the lowest worldwide age adjusted rates of colorectal cancer in 2012 were in sub-Saharan Africa, Gambia and Mozambique, where polio has not been eradicated. In the current study, poliomyelitis incidence in US states before the introduction of polio vaccine was analyzed.

Reported cases of poliomyelitis per 100,000 population by state 1932-1951 were from Centers for Disease Control. Colorectal cancer deaths per 100,000 in men (2005-2009) by US State are from the American Cancer Society. US state overweight and obesity data are from the Centers for Disease Control and Prevention (CDC). Smoking data are from the CDC.

By US state, colorectal cancer incidence per 100,000 in men for 2005-2009 was inversely correlated with reported cases of poliomyelitis per 100,000 for 1932-1951 (r=-0.311, p=0.032). Colorectal cancer deaths per 100,000 in men in 2005-2009 were also inversely correlated with reported cases of poliomyelitis per 100,000 by state for 1932-1951 (r=-0.493, p<0.001). The relationship between colorectal cancer deaths and polio incidence was significant (β=-0.196, p=0.028) and independent of the effects of smoking (β=0.289, p=0.012) and overweight (β=0.547, p<0.001). The relationship in females with colorectal cancer was identical.

Polio virus infection of cells of the colon may induce some degree of resistance to the development of colon cancer decades later. The effect of polio virus infection seems to be especially potent in reducing the rate of death from colon cancer.