The association was seen even after the researchers took into account higher body weight.
For the study, the researchers took 164 women and divided them into three groups.
In 1999, 4,682 researchers from all over the world took advantage of it.
The researchers do not take a position about which explanation is more likely.
Researchers from seven universities are taking part in the study.
In general, researchers just can't take much credit or blame.
Then the researchers took their study, published last week in the journal Science, a step further.
Researchers have also taken a look at how many young men go to - and finish - college.
The researchers took a chance, and no action was taken to cut off their universities' funds.
Researchers take into account every factor like this that they can think of.