That protection applies not only to the charts of the living or recently deceased, but also to records dating to the 1700s and 1800s. Which poses a problem for historians and researchers such as Segesser, who say the public is being denied important information that could help guide current health-care practices and policies.
One morning in late February, Segesser was escorted up a narrow staircase into the hidden recesses of Pennsylvania Hospital. Her guide, Stacey Peeples, the hospital's curator and lead archivist, opened a series of locked doors until she came to the last one.
Taped to it was a piece of white paper, folded in half, bearing a quote from George Orwell's 1984: "He who controls the past controls the future. He who controls the present controls the past."
On this floor, the hospital stores 261 years of medical history - silver surgical instruments, Frankensteinian electric-shock machines, herbal prescriptions, bound volumes containing minutes of board meetings written with quill pens in balletic script, and hundreds of thousands of patient records.
Few people ever get to see any of it.
Although Peeples was able to open admission records providing basic information - patients' sex, age, and suspected ailments - she could not allow access to detailed charts.
In England, where Segesser also is conducting this research, she said, medical records are fair game 75 years after the patient's death.
But in the United States, the privacy protection extends back forever.
"This is a huge issue," said Howard Markel, director of the Center for the History of Medicine at the University of Michigan. "It's closing off some of the most intriguing avenues in the history of medicine research."
Markel, author of The Anatomy of Addiction, is studying influenza epidemics. He said he had been prevented from examining records at several major hospitals even when he promised that personal information, such as patient names, would not be used.
"Looking at some of these charts not only allows you to re-create how patients were treated in a particular era," Markel said, "but the data therein might answer questions for today's patients."
For instance, in planning for a future pandemic, he said, it would be useful to examine pathology records and see whether victims of previous outbreaks died of flu or secondary infections that could be treated with antibiotics.
Two years ago, in response to the outcry from U.S. researchers, the U.S. Department of Health and Human Services' Office of Civil Rights proposed a change to the regulations that would allow access 50 years after a patient's estate closes.
That amendment has yet to be enacted.
The civil rights office's latest projection was that the rule would be made final this month. But that is unlikely, a spokesman said, because it is only one in a bundle of changes.
HIPAA rules already make some allowances for researchers to access patient files.
In Boston, Edward Ryan, an infectious-disease doctor, professor at the Harvard School of Public Health, and director of tropical medicine for Massachusetts General Hospital, says he has not had a problem obtaining permission to review charts for his studies of cholera.
The hospital merely requires him to submit a proposal to a special administrative board, and explain the nature of the research and the justification for opening the records.
"Although at some level it may seem ridiculous to protect records after 200 years, people come to a hospital for personalized medical care," Ryan said. "And the confidentiality of the doctor-patient relationship should not end after the patient dies."
Some hospitals, advised by risk-averse attorneys, interpret the privacy rules more narrowly than others. The consequences of violating HIPAA can trigger a federal investigation with substantial potential fines.
"It's the law of unintended consequences," said Gary Stephenson, a spokesman for Johns Hopkins University. "No one thought of this when the law was instituted."
Like Massachusetts General, Hopkins allows researchers to apply for access to old records, but the administrative process can be daunting. And even when the research is legitimate, some topics of study are less likely than others to win approval.
Hospitals are extremely cautious about opening records of patients who had sexually transmitted diseases, genetic defects, or psychiatric problems.
Aliza Schwartzman, associate general counsel at the University of Pennsylvania Health System, said that the current regulations do not give hospital attorneys much leeway. "We've always had that fine line with what we can allow people to see. They give me a little bit of rope, but I can't say to anyone, 'Yes, I can provide access,' because legally, I'm not allowed to."
Even when the federal regulations ease, as they are expected to, the stricter laws that some states have will prevail.
So it is likely that in Pennsylvania, where privacy rules, particularly those governing mental-health records, are very tough, many files will remain locked.
"The laws in Pennsylvania are structured so courts cannot balance the social good of disclosing vs. the bad. There are just blanket rules," said Joseph Kelley III, a Philadelphia lawyer who specializes in mental-health issues.
Representatives from the state Department of Public Welfare, which oversees mental health, and the state Department of Health said that for now, there are no plans to change the rules. If HIPAA regulations change, they said, the state might reconsider.
During her morning in the hospital's archives, Segesser was not permitted into most of the rooms. Many items are kept hidden for security reasons, such as a caned armchair that belonged to William Penn.
Other pieces in the collection make a public appearance from time to time when Peeples, the archivist, assembles temporary exhibits.
The original petition to form the hospital, written by Benjamin Franklin, and a Penn family land grant from 1767 will be on loan to the Philadelphia Antiques Show in April, she said. And the hospital's historic library, which is open for public tours, houses a rotating selection from the archives. The current one, open through June 1, "Flowers to Pharmacy," contains botanical illustrations and documents showing how 18th-century doctors used medicinal plants.
But the trove of patient records that might contain the clues about eating disorders?
"I hold out the hope," Peeples said, "that a lot of the laws that close off these records will change to grandfather these in."
For now, though, her hands are tied.
Segesser did find useful material in the admission notes she was permitted to review. Still, she left frustrated.
"I appreciate the need for patient confidentiality, of course I do," she said. "But when someone was in Pennsylvania Hospital in 1752, the chance of their information having a negative effect on anyone alive today is very slim."
Markel, the medical historian from Michigan, said he was sure that he spoke on behalf of many of his colleagues when he said he would welcome a HIPAA rule change. "But what has to be done, not only on the federal level but with hospital administrators and lawyers, is to clarify what are the dos and don'ts. I think that would be better not only for me and other historians, but for the health of the nation."
Contact Melissa Dribben at 215-854-2590 or email@example.com.