Night shifts, jet lag may 'turn on' genes that encourage cancer cells to multiply, study says

Night shifts and jet lag may fuel tumor growth, a new study suggests.

Disrupting the rhythms that fuel our sleeping and waking cycles may "turn on" genes that encourage cancer cells to multiply and "turn off" the ones that block tumor growth, according to a University of Pennsylvania study.

For example, women who do night shift work are at a 5 to 20% greater risk of developing breast cancer than the general population.

The study suggests even jet lag may make tumors grow faster.