At her annual visit, the patient’s doctor asks if she plans to continue having regular mammograms to screen for breast cancer lifestyle choices, and then reminds her that it’s been almost 10 years since her last colonoscopy.

She’s 76. Hmmm.

The patient’s age alone may be an argument against further mammogram appointments. The independent and influential U.S. Preventive Services Task Force, in its latest draft guidelines, recommends screening mammograms for women 40 to 74, but says “the current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women age 75 years or older.”

Screening for colorectal cancer, with a colonoscopy or with a less invasive test, becomes similarly questionable at advanced ages. The task force gives it a C grade for those 76 to 85, meaning there’s “at least moderate certainty that the net benefit is small.” It should only be offered selectively, the guidelines say.

But what else is true about this hypothetical woman? Is she playing tennis twice a week? Does she have heart disease? Did her parents live well into their 90s? Does she smoke?

Any or all such factors affect her life expectancy, which in turn could make future cancer screenings either useful, pointless or actually harmful. The same considerations apply to an array of health decisions at older ages, including those involving drug regimens, surgeries, other treatments and screenings.

“It doesn’t make sense to draw these lines by age,” said Dr. Steven Woloshin, an internist and director of the Center for Medicine and Media at the Dartmouth Institute. “It’s age plus other factors that limit your life.”

Slowly, therefore, some medical associations and health advocacy groups have begun to shift their approaches, basing recommendations about tests and treatments on life expectancy rather than simply age.

“Life expectancy gives us more information than age alone,” said Dr. Sei Lee, a geriatrician at the University of California, San Francisco. “It leads to better decision making more often.”

Some recent task force recommendations already reflect this broader view. For older people undergoing lung cancer tests, for instance, the guidelines advise considering factors like smoking history and “a health problem that substantially limits life expectancy” in deciding when to discontinue screening.

The task force’s colorectal screening guidelines call for considering an older patient’s “health status (e.g., life expectancy, co-morbid conditions), prior screening status and individual preferences.”

The American College of Physicians similarly incorporates life expectancy into its prostate cancer screening guidelines; so does the American Cancer Society, in its guidelines for breast cancer screening for women over 55.

But how does that 76-year-old woman know how long she will live? How does anybody know?

A 75-year-old has an average life expectancy of 12 years. But when Dr. Eric Widera, a geriatrician at the University of California, San Francisco, analyzed census data from 2019, he found enormous variation.

The data shows that the least healthy 75-year-olds, those in the lowest 10 percent, were likely to die in about three years. Those in the top 10 percent would probably live for another 20 or so.

All these predictions are based on averages and can’t pinpoint life expectancy for individuals. But just as doctors constantly use risk calculators to decide, say, whether to prescribe drugs to prevent osteoporosis or heart disease, consumers can use online tools to get ballpark estimates.

For instance, Dr. Woloshin and his late wife and research partner, Dr. Lisa Schwartz, helped the National Cancer Institute develop the Know Your Chances calculator, which went online in 2015. Initially, it used age, sex and race (but only two, Black or white, because of limited data) to predict the odds of dying from specific common diseases and the odds of mortality overall over a span of five to 20 years.

The institute recently revised the calculator to add smoking status, a critical factor in life expectancy and one that, unlike the other criteria, users have some control over.

“Personal lifestyle choices are driven by priorities and fears, but objective information can help inform those decisions,” said Dr. Barnett Kramer, an oncologist who directed the institute’s Division of Cancer Prevention when it published the calculator.

He called it “an antidote to some of the fear-mongering campaigns that patients see all the time on television,” courtesy of drug manufacturers, medical organizations, advocacy groups and alarmist media reports. “The more information they can glean from these tables, the more they can arm themselves against health care lifestyle choices that don’t help them,” Dr. Kramer said. Unnecessary testing, he pointed out, can lead to overdiagnosis and overtreatment.

A number of health institutions and groups provide disease-specific online calculators. The American College of Cardiology offers a “risk estimator” for cardiovascular disease. A National Cancer Institute calculator assesses breast cancer risk, and Memorial Sloan Kettering Cancer Center provides one for lung cancer.

Calculators that look at single diseases, however, don’t usually compare the risks to those of mortality from other causes. “They don’t give you the context,” Dr. Woloshin said.

Probably the broadest online tool for estimating life expectancy in older adults is ePrognosis, developed in 2011 by Dr. Widera, Dr. Lee and several other geriatricians and researchers. Intended for use by health care professionals but also available to consumers, it offers about two dozen validated geriatric scales that estimate mortality and disability.

The calculators, some for patients living on their own and others for those in nursing homes or hospitals, incorporate considerable information about health history and current functional ability. Helpfully, there’s a “time to benefit” instrument that illustrates which screenings and interventions may remain useful at specific life expectancies.

Consider our hypothetical 76-year-old. If she’s a healthy never-smoker who is experiencing no problems with daily activities and is able, among other things, to walk a quarter mile without difficulty, a mortality scale on ePrognosis shows that her extended life expectancy makes mammography a reasonable choice, regardless of what age guidelines say.

“The risk of just using age as a cutoff means we’re sometimes undertreating” very healthy seniors, Dr. Widera said.

If she’s a former smoker with lung disease, diabetes and limited mobility, on the other hand, the calculator indicates that while she probably should continue taking a statin, she can end breast cancer screening.

“Competing mortality” — the chance that another illness will cause her death before the one being screened for — means that she will probably not live long enough to see a benefit.

Of course, patients will continue to make decisions of their own. Life expectancy is a guide, not a limit on medical care. Some older people don’t ever want to stop screenings, even when the data shows they’re no longer helpful.

And some have exactly zero interest in discussing their life expectancy; so do some of their doctors. Either party can over- or underestimate risks and benefits.

“Patients simply will say, ‘I had a great-uncle who lived to 103,’” Dr. Kramer recalled. “Or if you tell someone, ‘Your chances of long-term survival are one in 1,000,’ a strong psychological mechanism leads people to say, ‘Oh thank God, I thought it was hopeless.’ I saw it all the time.”

But for those seeking to make health decisions on evidence-based calculations, the online tools provide valuable context beyond age alone. Considering projected life expectancy, “You’ll know what to focus on, as opposed to being frightened by whatever’s in the news that day,” Dr. Woloshin said. “It anchors you.”

The developers want patients to discuss these predictions with their medical providers, however, and caution against making decisions without their involvement.

“This is meant to be a jumping-off point” for conversations, Dr. Woloshin said. “It’s possible to make much more informed decisions — but you need some help.”

Cheri Pies, a professor of public health who broke barriers with her landmark 1985 book, “Considering Parenthood: A Workbook for Lesbians,” a bible of the “gayby boom” of the 1980s and beyond, died on July 4 at her home in Berkeley, Calif. She was 73.

The cause was cancer, said her wife, Melina Linder.

Later in life, Dr. Pies (her first name was pronounced “Sherry”) became a pioneering researcher and professor at the University of California, Berkeley School of Public Health, investigating the effects of economic and racial inequality in matters like infant mortality and health over generations.

But she made her name decades before her turn toward academia with her groundbreaking book. That journey began in the 1970s, when Dr. Pies was working as a health educator for Planned Parenthood, counseling straight women considering motherhood.

Her focus began to shift in 1978, after her female partner adopted a daughter. At that time, the concept of openly gay parents was still mostly unheard-of in the culture at large.

Just that year, New York became the first state to say it would not reject applications for adoption solely on the basis of homosexuality. A year later, a gay couple in California broke barriers as the first known to jointly adopt a child.

Dr. Pies was struck by the lack of support available to same-sex parents, as well as the lack of basic information about the unique challenges they face. She began running workshops in her home in Oakland, Calif., advertising them with fliers in women’s bookshops and other places where lesbians gathered.

By the early 1980s, word of her work had spread beyond the Bay Area, and she was bombarded with letters and phone calls from lesbians around the country. In response, Dr. Pies compiled her teachings and experiences into a book. “Considering Parenthood: A Workbook for Lesbians,” published by the lesbian feminist press Spinsters Ink, provided practical advice on a wide range of topics, including the use of sperm donors, legal issues surrounding adoption, and ways to build a support network.

The book, which appeared 30 years before same-sex marriage was legalized nationally, opened the floodgates for countless other books about L.G.B.T.Q. parenthood.

“She was absolutely a pioneer, and those of us who came later built on her work,” G. Dorsey Green, a psychologist and author of “The Lesbian Parenting Book” (with D. Merilee Clunis, 2003), was quoted as saying in an obituary about Dr. Pies on Mombian, a website for lesbian parents. “I would recommend her book to clients. That was when lesbian couples were just starting to think about having children as out lesbians. Cheri started that conversation.”

Dr. Pies, who earned a master’s degree in social work from Boston University in 1976, would eventually turn to academia, receiving another master’s degree, in maternal and child health, from Berkeley in 1985 and a doctorate in health education there in 1993.

She was serving as the director of family, maternal and child health programs for Contra Costa County, which borders Berkeley and Oakland, when she heard a lecture in 2003 by Dr. Michael C. Lu, who would go on to become the dean of the Berkeley School of Public Health.

Dr. Lu spoke about a concept called life course theory, which centers on the idea that the social and economic conditions at each stage in life, starting with infancy, can have powerful, lasting effects over generations. “What surrounds us shapes us,” Dr. Pies explained in a 2014 lecture at the University of Alabama at Birmingham. “Some people would say your ZIP code is more important than your genetic code.”

At Berkeley, Dr. Pies would eventually collaborate with Dr. Lu and others to create the Best Babies Zone initiative, a groundbreaking program that would study — and, ideally, improve — health conditions in economically challenged neighborhoods around the country.

In 2012, she became the program’s principal investigator, after Dr. Lu took a post in the Obama administration. The initiative included home health visits and work with community leaders to create parent-child play groups, improve park safety and enhance job-skills training. It began in Oakland, New Orleans and Cincinnati and had spread to six other cities by 2017, the year Dr. Pies retired from Berkeley. The program is still active today.

“There are people doing large-scale policy work around structural racism, trying to change policy and practice,” Dr. Pies said in an interview published on the Berkeley School of Public Health website in April. “Best Babies Zone is at the other end of the spectrum, going small-scale to make change for people who can’t wait for policy change to happen.”

The high incidence of low birth weight and sudden infant death syndrome in such communities was a focus of the program. “Babies are the canary in the mine,” Dr. Pies said in her University of Alabama speech. “If babies aren’t born healthy, you know that something isn’t right in the community.”

Cheramy Anne Pies was born on Nov. 26, 1949, in Los Angeles, the second of three daughters of Morris Pies, a physician, and Doris (Naboshek) Pies, a nurse. (She later changed her name to Cheri.)

Growing up in Encino, in the San Fernando Valley, the outgoing, ebullient Cheri was a fan of movies, particularly musicals like “My Fair Lady,” and got an early taste of the medical profession working as a receptionist in her father’s office.

After graduating from nearby Birmingham High School, she enrolled at Berkeley in 1967, where she earned a bachelor’s degree in social science in 1971.

Berkeley at the time was a cauldron of Vietnam War-era political passions, after the Free Speech Movement protests that rocked the campus starting in 1964. “Even though I was not actively engaged in it, I was certainly exposed to the politics of it,” she later said of the movement.

In addition to her wife, Dr. Pies is survived by her sisters, Lois Goldberg and Stacy Pies.

She would eventually channel Berkeley’s 1960s spirit of activism as an author and professor, working to improve the lives of openly lesbian parents of the 1980s and beyond — whose numbers swelled so quickly that by 1996, Newsweek magazine would report that an estimated six million to 14 million children in the United States had at least one gay parent.

“Adoption agencies report more and more inquiries from prospective parents — especially men — who identify themselves as gay,” the article read, “and sperm banks say they’re in the midst of what some call a ‘gayby boom’ propelled by lesbians.”

Many of that generation would acknowledge their debt to Dr. Pies for the rest of her life, Ms. Linder said in a phone interview: “Cheri and I could be anywhere in the world — on a hike in New Zealand or just walking in the Berkeley Hills — and people would see her and stop to thank her, saying how Ben or Alice or whoever would not be in their life were it not for Cheri.”

In 2004, Gilead Sciences decided to stop pursuing a new H.I.V. therapy. The public explanation was that it wasn’t sufficiently different from an existing treatment to warrant further development.

In private, though, something else was at play. Gilead had devised a plan to delay the new drug’s release to maximize profits, even though executives had reason to believe it might turn out to be safer for patients, according to a trove of internal documents made public in litigation against the company.

Gilead, one of the world’s largest drugmakers, appeared to be embracing a well-worn industry tactic: gaming the U.S. patent system to protect lucrative monopolies on best-selling drugs.

At the time, Gilead already had a pair of blockbuster H.I.V. treatments, both of which were underpinned by a version of a drug called tenofovir. The first of those treatments was set to lose patent protection in 2017, at which point competitors would be free to introduce cheaper alternatives.

The promising drug, then in the early stages of testing, was an updated version of tenofovir. Gilead executives knew it had the potential to be less toxic to patients’ kidneys and bones than the earlier iteration, according to internal memos unearthed by lawyers who are suing Gilead on behalf of patients.

Despite those possible benefits, executives concluded that the new version risked competing with the company’s existing, patent-protected formulation. If they delayed the new product’s release until shortly before the existing patents expired, the company could substantially increase the period of time in which at least one of its H.I.V. treatments remained protected by patents.

The “patent extension strategy,” as the Gilead documents repeatedly called it, would allow the company to keep prices high for its tenofovir-based drugs. Gilead could switch patients to its new drug just before cheap generics hit the market. By putting tenofovir on a path to remain a moneymaking juggernaut for decades, the strategy was potentially worth billions of dollars.

Gilead ended up introducing a version of the new treatment in 2015, nearly a decade after it might have become available if the company had not paused development in 2004. Its patents now extend until at least 2031.

The delayed release of the new treatment is now the subject of state and federal lawsuits in which some 26,000 patients who took Gilead’s older H.I.V. drugs claim that the company unnecessarily exposed them to kidney and bone problems.

In court filings, Gilead’s lawyers said that the allegations were meritless. They denied that the company halted the drug’s development to increase profits. They cited a 2004 internal memo that estimated Gilead could increase its revenue by $1 billion over six years if it released the new version in 2008.

“Had Gilead been motivated by profit alone, as plaintiffs contend, the logical decision would have been to expedite” the new version’s development, the lawyers wrote.

Gilead’s top lawyer, Deborah Telman, said in a statement that the company’s “research and development decisions have always been, and continue to be, guided by our focus on delivering safe and effective medicines for the people who prescribe and use them.”

Today, a generation of expensive Gilead drugs containing the new iteration of tenofovir account for half of the market for H.I.V. treatment and prevention, according to IQVIA, an industry data provider. One widely used product, Descovy, has a sticker price of $26,000 annually. Generic versions of its predecessor, Truvada, whose patents have expired, now cost less than $400 a year.

If Gilead had moved ahead with its development of the updated iteration of the drug back in 2004, its patents either would have expired by now or would soon do so.

“We should all take a step back and ask: How did we allow this to happen?” said James Krellenstein, a longtime AIDS activist who has advised lawyers suing Gilead. He added, “This is what happens when a company intentionally delays the development of an H.I.V. drug for monopolistic purposes.”

Gilead’s apparent maneuver with tenofovir is so common in the pharmaceutical industry that it has a name: product hopping. Companies ride out their monopoly on a medication and then, shortly before the arrival of generic competition, they switch — or “hop” — patients over to a more recently patented version of the drug to prolong the monopoly.

The drug maker Merck, for example, is developing a version of its blockbuster cancer drug Keytruda that can be injected under the skin and is likely to extend the company’s revenue streams for years after the infused version of the drug faces its first competition from other companies in 2028. (Julie Cunningham, a spokeswoman for Merck, denied that it is engaged in product hopping and said the new version is “a novel innovation aimed at providing a greater level of convenience for patients and their families.”)

Christopher Morten, an expert in pharmaceutical patent law at Columbia University, said the Gilead case shows how the U.S. patent system creates incentives for companies to decelerate innovation.

“There’s something profoundly wrong that happened here,” said Mr. Morten, who provides pro bono legal services to an H.I.V. advocacy group that in 2019 unsuccessfully challenged Gilead’s efforts to extend the life of its patents. “The patent system actually encouraged Gilead to delay the development and launch of a new product.”

David Swisher, who lives in Central Florida, is one of the plaintiffs suing Gilead in federal court. He took Truvada for 12 years, starting in 2004, and developed kidney disease and osteoporosis. Four years ago, when he was 62, he said, his doctor told him he had “the bones of a 90-year-old woman.”

It was not until 2016, when Descovy was finally on the market, that Mr. Swisher switched off Truvada, which he believed was harming him. By that time, he said, he had grown too sick to work and had retired from his job as an airline operations manager.

“I feel like that whole time was taken away from me,” he said.

First synthesized in the 1980s by researchers in what was then Czechoslovakia, tenofovir was the springboard for Gilead’s dominance in the market for treating and preventing H.I.V.

In 2001, the Food and Drug Administration for the first time approved a product containing Gilead’s first iteration of tenofovir. Four more would follow. The drugs prevent the replication of H.I.V., the virus that causes AIDS.

Those became game-changers in the fight against AIDS, credited with saving millions of lives worldwide. The drugs came to be used not only as a treatment but also as a prophylactic for those at risk of getting infected.

But a small percentage of patients who were taking the drug to treat H.I.V. developed kidney and bone problems. It proved especially risky when combined with booster drugs to enhance its effectiveness — a practice that was once common but has since fallen out of favor. The World Health Organization and the U.S. National Institutes of Health discourage the use of the original version of tenofovir in people with brittle bones or kidney disease.

The newer version doesn’t cause those problems, but it can cause weight gain and elevated cholesterol levels. For most people, experts say, the two tenofovir-based drugs — the first known as T.D.F., the second called T.A.F. — offer roughly equal risks and benefits.

The internal company records from the early 2000s show that Gilead executives at times wrestled with whether to rush the new formulation to market. At some points, the documents cast the two iterations of tenofovir as similar from a safety standpoint.

But other memos indicate that the company believed the updated formula was less toxic, based on studies in laboratories and on animals. Those studies showed that the newer formulation had two advantages that could reduce side effects. It was much better than the original at delivering tenofovir to its target cells, meaning that much less of it leaked into the bloodstream, where it could travel to kidneys and bones. And it could be given at a lower dose.

The new version “may translate into a better side effect profile and less drug-related toxicity,” read an internal memo in 2002.

That same year, the first human clinical trial of the newer version got underway. A Gilead employee mapped out a development timeline that would have brought the newer formulation to market in 2006.

But in 2003, Gilead executives began to sour on rushing it forward. They worried that doing so would “ultimately cannibalize” the growing market for the older version of tenofovir, according to minutes from an internal meeting. Gilead’s head of research at the time, Norbert Bischofberger, instructed company analysts to explore the new formulation’s potential as an intellectual property “extension strategy,” according to a colleague’s email.

That analysis resulted in a September 2003 memo that described how Gilead would develop the newer formulation to “replace” the original, with development “timed such that it is launched in 2015.” In a best-case scenario, company analysts calculated, their strategy would generate more than $1 billion in annual profits between 2018 and 2020.

Gilead moved to resurrect the newer formulation in 2010, putting it on track for its 2015 release. John Milligan, Gilead’s president and future chief executive, told investors that it would be a “kinder, gentler version” of tenofovir.

After winning regulatory approvals, the company embarked on a successful marketing campaign, aimed at doctors, that promoted its new iteration as safer for kidneys and bones than the original.

By 2021, according to Ipsos, a market research firm, nearly half a million H.I.V. patients in the United States were taking Gilead products containing the new version of tenofovir.

Susan C. Beachy contributed research.