Researchers at the Weill Cornell Medical College in New York suggest that incidence of rectal cancer among people below the age of 40 is on the rise across the United States.

Though the actual number of cases continues to be small, the study claims that a young person's chance fo developing the disease has grown in the recent years, says Dr. David L. Sherr, assistant professor of radiation oncology at the college, who co-authored the study.

If the patients under 40 have rectal bleeding then they should take it as seriously as in the case of a 50-year-old and requires some immediate investigation, says Dr. Sherr in the study report published in the medical journal Cancer.

Colon and rectal cancers are usually seen among the older people across the United States and is known to cause the second largest number of deaths in the country.

The study suggests that as against about 300 cases of rectal cancer diagnosed annually in people below 40 during the period between 1973 and 2005, the number grown by about ten percent each year since 2006. The risk of a younger person getting rectal cancer in the last two decades was just about four in a million.

The study does not provide any clear answers about the reasons for this rise in the incidence of rectal cancer and categorically ruled out sexual practices as a possible culprit. Sherr said rectal cancer was different from anal cancer, which often spreads through a virus during sex.

It was suggested that the rising obesity rates could play a role in rectal cancer because heavier bodies are linked to the ailment. The study also indicated no change in the rates of cancer among people over 40 years of age. The study team believes that doctors should be more aware of the possible risk among younger patients and ensure prompt investigation of rectal bleeding.