( sity. Jason Yee a graduate student in ...)Temperament linked to onset of cancer and early death in female rats

For their study, the researchers selected 81 female Sprague-Dawley rat pups. The breed is prone to development of breast and pituitary tumors. In order to minimize the differences in temperament that are accountable to differences between rat families, the researchers compared behavior among sisters.

The rats were tested at 20 days and 11 months of age in a cage to see how willing they were to explore a new environment, which contained non-threatening items such as toys. The researchers measured adventuresomeness by recording how far the rats wandered in the environment.

They found that by age 390 days, middle age for rats, 80 percent of the fearful rats had mammary cancer while only 38 percent of the adventuresome rats had the illness. The fearful rats had a life span of 573 days, versus 850 for the adventuresome rats. They found similar life span results for females with pituitary tumors.

The researchers also monitored ovarian cycles daily from the time the rats were 55 days old until they were 450 days old. In studying their ovarian cycles, the scholars found that during puberty, the fearful rats were twice as likely as the adventuresome rats to have irregular cycles (52 percent, versus 22 percent). The cycles stabilized after the rats reached adulthood, and then became differentiated again during middle age with the fearful rats having irregular cycles more often. The aging affects on reproduction were also accelerated in the fearful rats.

In an earlier study, University of Chicago researchers looked at the lifespan of male rats and found that the adventuresome males lived longer. Because the male rats died of a variety of diseases, they could not establish a reason for the differences. The new study links personality specifically with cancer.