Ms. Faye is 75, and her mother, Yetta Meisel, a widow, is 99. The former art teacher fills her days helping her mother bathe, making her meals, picking up medications, scheduling home aides and transporting a wheelchair for excursions.

“Ironically, we did not think she would live this long — she wasn’t all that healthy,” Ms. Faye said, noting years of painful stomach ailments and arthritis. Besides difficulty walking and some cognitive impairment, “she is doing fantastic.”

Ms. Faye and her mother are part of what many experts say is a growing phenomenon: Children in their 60s and 70s who are spending their retirement years caring for parents who are in their 90s and beyond.

“People in their late 60s and early 70s thought this would be a time of life when some of their responsibilities would drop off,” Dr. Boerner said. “Even though it may be a gift to still have your parents, it can be really rough.”

Besides forcing Ms. Faye to abandon her retirement dreams, her mother’s longevity has taken a financial toll.

She cares for her mother three days a week, and Mrs. Meisel’s Social Security and the state program pay the balance for her care. The $200 left over each month from Mrs. Meisel’s Social Security payment does not cover the rest of her expenses; Ms. Faye said she chips in from a $1,000 monthly pension she receives from a government administrative job.