Ms. Daruda had them removed in 2013, and said most, but not all, of her symptoms have lessened.
Another patient activist, Jamee Cook, now 41, had implant surgery for cosmetic reasons when she was 21. Over the next few years she developed so many health problems, including fatigue, memory lapses, migraines and numbness in her hands, that she had to quit her job as a paramedic.
After having the implants removed in 2015, she said, her health has improved. Though she still has some bad days, Ms. Cook said, “It’s been like a 180.”
Silicone-filled breast implants were first marketed in the United States in the 1960s. Over the next few decades, reports of illness emerged. In 1992, silicone implants were banned, except for reconstruction after mastectomy or to replace a previous implant, and then only in clinical trials.
A flood of lawsuits followed.
Studies conducted afterward generally found no link to connective tissue disease, but a few did suggest a connection. In 1999, the Institute of Medicine, then part of the National Academy of Sciences, concluded that overall, there was no evidence that breast implants caused connective tissue disease, cancer, immune disorders or other ailments.
In 2006, silicone implants came back on the market. But manufacturers were required to follow large numbers of women for seven to 10 years, as a condition for F.D.A. approval. Deficiencies in the studies have now prompted the agency to send warning letters to two of the four companies approved to market breast implants in the United States.
One warning letter, sent to the manufacturer Sientra, of Santa Barbara, Calif. on Tuesday, said the company had not kept enough patients in its study of an implant approved in 2012, and warned that if the follow-up monitoring did not improve, the agency could withdraw approval of the implant, effectively taking it off the market.
Rosalyn d’Incelli, vice president of clinical and medical affairs for Sientra, said the company tries to retain patients in follow-up studies by compensating them, contacting them several times a year through email, phone calls, letters and postcards, and transferring them to doctors in more convenient locations. But she said that patients’ work obligations, child care, lack of transportation and other issues often present obstacles.