Generational differences and the economy are shifting more responsibilities for children from their parents to grandparents, according to a new survey。

More than one-third of grandparents aged 50 and older contribute financially to their grandchildren's' upbringing, and 11 percent have a grandchild living with them, the poll by AARP, the lobbying group for 36 million older US citizens, showed。

Forty percent of people who responded to the telephone survey, whose average age was 69, reported spending more than $500 on grandchildren over the past year beyond traditional gifts. Education costs accounted for 53 percent, daily expenses for 37 percent and medical and dental costs for 23 percent。

Sixteen percent provided daycare for grandchildren。

"They are the safety net for American families, helping to pay for practical expenses and necessities," said Amy Goyer, AARP's multigenerational and family issues expert。

"We see many providing daycare services, while growing numbers even have grandchildren living with them," she said, referring to the 16 percent who watch their grandchildren while the parents are at work or school。

Overall nearly 90 percent of the 1,904 grandparents questioned said they play a very or somewhat important role in their grandchildren's lives, and about 70 percent live within 50 miles of the closest one。

The poll conducted by Woelfel Research Inc. also showed that grandparents were increasingly keyed in to the younger generation's life issues and preferred ways of communicating。