Colon cancer risk runs in families, and it's not just a parent or sibling having had the disease that should concern you.

If you have a second- or third-degree relative who had colon cancer at an early age, your odds of having the disease substantially increase, a new study finds.

First-degree relatives include parents, children and siblings. Second-degree relatives include aunts, uncles, grandparents, grandchildren, nieces and nephews. Third-degree relatives include first cousins, great-grandparents and great-grandchildren.

"Our study provides new insight into the magnitude of risk for more distant relatives of colorectal cancer cases, and in particular, for relatives of cases who were diagnosed before age 50," said researcher Heather Ochs-Balcom, an associate professor of epidemiology and environmental health with the University at Buffalo (N.Y.) School of Public Health and Health Professions.

"This work is important given the rising rates of early-onset colorectal cancer," she said in a university news release. The researchers, from the University at Buffalo and the University of Utah, referred to early-onset colon cancer as cases diagnosed before age 50.

First-degree relatives of someone diagnosed with early-onset colon cancer are six times more likely to develop colon cancer before age 50; second-degree relatives are three times more likely, and third-degree relatives are about 1.5 times more likely, investigators found.

For the study, they reviewed more than 1,500 early-onset colon cancer cases in the Utah Cancer Registry.

Researchers also found that people have a 2.6-fold higher risk of colon cancer at any age if they have a first-degree relative with early-onset colon cancer. And the risk is about two times greater for second-degree relatives, and 1.3 times greater for third-degree relatives.

These findings suggest that a colonoscopy screening before age 50 may be beneficial for second-degree relatives and possibly third-degree relatives of someone who developed colon cancer, not just immediate family members.

The report was published in August in the journal Cancer Epidemiology.