A landmark new study paints a dramatic picture of family caregivers: Nearly 44 million adults in the US are providing personal assistance for family members with disabilities or other care needs. That’s more than one out of every six adults. More than 34 million care for frail elders and nearly 4 million help children with disabilities. About 6.5 million care for both.

The typical family caregiver is a 49-year-old woman who is assisting a parent or in-law and working at a paid job. She reports spending an average of about 24 hours-a-week providing personal assistance such as bathing or dressing or helping with activities such as shopping or rides. Almost six in 10 say they perform nursing or other complex care tasks, such as giving oral medicines or injections, wound care, or operating medical equipment.

The typical caregiver has been helping a parent or spouse for four years.

Most work full-time but six in 10 say caregiving has affected their ability to do their jobs. About half say they’ve had to take occasional time off, 15 percent have taken leaves of absences, and 14 percent have had to reduce work hours or change jobs as a result of their caregiving.

The study, Caregiving in the U.S., was done jointly by the National Alliance for Caregiving and the AARP Public Policy Institute. The researchers did extensive interviews with more than 1,200 family caregivers in late 2014. The survey follows similar studies done in 1997, 2004, and 2007.

About half of all those caring for adults say they get help from other relatives or friends. But only about one-third say their loved ones have aides, housekeepers, or other paid assistance (some report both paid and unpaid help). A third of family caregivers say they do it alone—they get no help from anyone.

The typical care recipient is a 69-year-old woman, though nearly half of caregivers say they are aiding a loved one who is 75 or older. Half live in their own home and a third live in their caregiver’s homes.  Only 5 percent lived in nursing homes and 3 percent in assisted living.

About 60 percent have some long-term physical condition, one-third have a short-term acute illness or injury, and almost one-quarter have memory problems. About half were hospitalized in the past year.

While it is useful to keep in mind that 49-year-old daughter who is the typical family caregiver, the study found important differences among those supporting their relatives.

For instance, while 60 percent were women, 40 percent were men. And while caregivers spend an average of about 24 hours-a-week helping relatives or friends, there is a lot of variation. Nearly one-quarter say they provide more than 40 hours-a-week of care.

And while the average duration of caregiving was four years, about one-third had been providing care for less than 6 months while about one-quarter has been at it for five years or more.

The report divided caregivers into those providing 20 hours or less and those who help for more than 20 hours, who it calls higher-hour caregivers. Not surprisingly, those doing the most reported higher levels of financial, physical, and emotional stress, and were more likely to cut back on their own paid work.

The biggest gap was between adult children helping parents and older adults caring for spouses or partners, who faced the biggest caregiving burden by far. For instance, they provided an average of nearly 45 hours-a-week of care, nearly twice the average. Caregivers who are themselves 75 or older are less likely to have paid help, more likely to act as medical advocates, and more likely to be managing their family finances than younger caregivers.

Two important caveats: The study reports answers to a survey. Caregivers were not asked to keep diaries or otherwise monitor their actual hours so their estimates of the time they give may not be perfectly accurate. Also, AARP and NAC warn that, because the methodology changed, it is not possible to compare the new results with the older surveys.

Still, this report is very valuable. In the national debates over long-term care, policymakers often forget that the vast majority of people with functional limitations live at home, and nearly all of them rely on family members and friends for support.

Caregiving in the U.S. is an important snapshot of those family members who are the bedrock of the nation’s long-term care system. It would crumble without them, and it is extremely helpful to know who they are and what they do.