Large families at higher risk for stomach cancer

Growing up with a large number of brothers and sisters may increase your chances of developing stomach cancer. A recent study suggests that early childhood infections -- which are more common in big families -- may contribute to cancer later in life.

After checking blood samples for bacterial infection, researchers discovered that men with certain strains of bacteria in their stomach who also had seven or more siblings were twice as likely to get stomach cancer than men with less than four brothers or sisters. According to Dr. Martin Blaser of New York University, who led the research, "This is a very carefully controlled study that clearly shows that there are factors in early childhood that affect the risk of developing cancer many decades later."

Anyone who's had kids in their house knows that children are bacteria magnets, and it only follows that younger children -- whose immune systems are less-developed -- are more susceptible to contracting infections from their older brothers and sisters. Dr. Blaser also speculates that bacteria transmitted from sibling to sibling is better adapted than that which is transmitted from a non-relative.

Add this to the list of things to blame your older brother or sister for later in life.