The median age of grandparents has stayed constant over the past century -- 45 years old, according to Handbook on Grandparenthood, edited by M. E. Szinovacz.
But increased life expectancy means modern grandparents are healthier, and many feel they are "younger in spirit."
"At 64, I'm probably a little bit healthier than my grandparents were," Palo Alto resident Beverly Nadine said.
Jan Kuersten, 58, of Mountain View, recently ran a half-marathon. She often "wrestle[s around on the floor" with her grandchildren and participates in physical, active events, such as camping, she said.
"Society a generation ago viewed people at a certain age as old. Baby boomers have continued to try and ignore the fact that we're getting old. We don't have expectations of what 50, 60 or 70 looks like," she said.
Grandparents today also think differently than their counterparts from the mid-20th century. Kuersten retired from her job as an administrator at Foothill College because she wanted time to focus on herself.
"It was almost incumbent on me to take the time I had to focus on things I wanted to do, to learn about who I am," she said.
Donne Davis of Menlo Park -- who founded a grandmothers' support group called the GaGa Sisterhood -- writes in her journal every day and occasionally writes freelance articles.
Donne's daughter, Deborah, describes her mother as "super active." She walks daily, does yoga and participates in dance classes.
Such vigorous lifestyles characterize the new generation of grandparents.
Cheri Goldberg, a member of the GaGa Sisterhood, flies to Pennsylvania every few months to visit her grandson.
"My grandparents were really old and not necessarily infirm, but they didn't travel well. They just stayed in their community and died in their community. They were not adventuresome," she said.