Women in their 40s whose breast cancer was spotted during a mammogram have better outcomes than those whose doctor found the disease during an exam.

A new study by Healthstat Consulting looked a nearly 2,000 women diagnosed with breast cancer between the ages of 40 and 49.

Over an 18 year period, the number of cancers diagnosed as Stage Zero increased over 60 percent, while cancers diagnosed at Stage Three dropped significantly, according to the study.

Also, women whose disease was detected by mammogram underwent less invasive treatment than those whose cancer was detected during an exam.

There has been a debate as to when women should start routine mammograms. Some organizations recommend age 40 while others say the biggest benefit is seen among women 50 and older.