Women who smoke for many years may increase their risk of developing breast cancer. New research shows that for women who had smoked for 40 years or longer, the risk of breast cancer was 60% higher than that of women who had never smoked.

Among those who smoked 20 cigarettes or more a day for 40 years, the increased risk rose to 83%.

“Our findings suggest that smoking of very long duration and high intensity may be associated with increased risk of …