If we take pre-menopausal and post-menopausal breast cancer then there was a 40 percent increased risk.

Our aim was to try to shed some more light on a possible cause for breast cancer, and we were able to show that left-handedness may play a role (among many other causes for breast cancer).

Still, it makes sense that something in the air might increase the risk of lung cancer because our lungs are just big filters.

If the link between light exposure and cancer risk can be confirmed, it could have an immediate impact on the production and use of artificial lighting in this country. This might include lighting with a wavelength and intensity that does not disrupt melatonin levels and internal timekeeping.

We are seeing a 50 percent reduction in the risk of colon cancer when we compare the top 20 percent of the population of women who in mid-life are exercising at the equivalent of an hour of walking a day,

A smoker who cuts back on the number of cigarettes by half reduces the risk of lung cancer not by half, but by 25 percent. So the risk is reduced but not just as much as the number of cigarettes.