Well over 40 million Americans provided care for an adult family member in 2009, representing an unpaid economic impact of approximately $450 billion, according to a new report from the AARP Public Policy Institute.

The report, entitled “Valuing the Invaluable: The Growing Contributions and Costs of Family Caregiving, 2011 Update,” describes the average family caregiver in 2009 as being a 49-year-old female juggling a full-time job and about 20 hours per week on caregiving tasks. There’s a price for double duty: In addition to the wage loss stemming from leaves of absence, caregivers experience increased rates of stress, depression, physical health problems, social isolation, competing demands and financial hardship. AARP notes that the economic downturn is a factor in a 67% increase in requests for help from caregiver support services from 2007 to 2009.

But the study notes that family caregivers are an essential part long-term care as a whole. If family caregivers were no longer available, the AARP estimates, the economic cost to the U.S. healthcare and long-term services and supports (LTSS) systems would increase astronomically.

“Family caregiving has been shown to help delay or prevent the use of nursing home care,” notes the report summary. “There is also growing recognition of the value of family members to the delivery of health care, and the ways in which families influence health care decisions, treatments and outcomes.”