Tracy Murphy was managing a nonprofit agency five years ago when her mother became seriously ill with heart problems. She promptly left her job to care for her, a task that has consumed Ms. Murphy ever since.

“For me, it was a no-brainer,” said Ms. Murphy, who lives in Syracuse. “When I was growing up she sacrificed for me.”

Ms. Murphy, 54, set aside her career aspirations, drained her savings account and eventually sold her gold jewelry to help make ends meet while shuttling her mother, who is 85, to doctors’ appointments and running errands.

“I always felt like I can find another job eventually — but I only have one mother,” she said.

Ms. Murphy is part of a small but economically significant group that is bucking a powerful decades-long movement of women of all ages into the labor market. In the years since the last recession began, many women like Ms. Murphy, in their late 40s and early 50s, have left the work force just as they were reaching their peak earning years.