There are more informal caregivers in the U.S. than ever before. Nearly one-third of the population provides some level of care, according to a new study.

The joint AARP/National Alliance for Caregiving study, released Tuesday, finds that 29% of the U.S. adult population—roughly 65.7 million adults—plays the role of caregiver. Roughly 70% of those care for someone over the age of 50, usually a relative (86%), and often a parent (36%). Caregivers are aging as well, the report finds. Among caregivers of adults, the average age of the caregiver rose from 46 in 2004 to 49 in the 2009 study. Approximately 66% of caregivers are women.