The findings reflect an evolution in the image of who makes up the sandwich generation. In the past, the burden typically was shouldered by a middle-aged woman who stayed at home caring for young children and aging parents. During the recession and the slow recovery, more adult children have returned home while they look for jobs. Even the percentage of married couples living in a parent’s home has returned to levels not seen since the turn of the 20th century.

Demographic changes are behind much of the shift, said Charles R. Pierret, director of longitudinal surveys at the Bureau of Labor Statistics, who has surveyed the sandwich generation. Longer life expectancy and delayed childbearing mean that more middle-aged people have dependent children and parents who are still living.

The change can have enormous financial implications for parents caught in the middle.