A number that should guide your health choices (it's not your age)

Life expectancy increasingly figures into calculations to determine whether screenings and treatments are appropriate. Here's how to find out yours.

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

She's 76 years old. Hmmm.

A patient's age alone can be an argument against further mammography appointments. The independent and influential United States Preventive Services Task Force, in its latest draft guidelines, recommends screening mammograms for women ages 40 to 74, but states that "current evidence is insufficient to assess the balance of benefits and harms of screening mammograms in women 75 years of age or older." Screening for colorectal cancer, with a colonoscopy or with a less invasive test, becomes equally questionable at older ages. The task force gives it a C rating for ages 76 to 85, meaning there is "at least moderate certainty that the net benefit is small." It should only be offered selectively, as per the guidelines.

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

Any or all of these factors affect her life expectancy, which could make future cancer screenings helpful, unnecessary, or even harmful. The same considerations apply to a range of health decisions at later ages, including those involving drug regimens, surgeries, other treatments, and screenings. "It's age and other factors that limit your life."

Slowly, therefore, some medical associations and health advocacy groups have begun to change their approaches, basing their test and treatment recommendations on life expectancy rather than simply age.

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

Some recent task force recommendations already reflect this broader view. For older adults undergoing screening for lung cancer, for example, the guidelines advise considering factors such as smoking history and "a health condition that significantly limits life expectancy" in deciding when to discontinue screening. evys1bk0">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 in women over 55.

But how does this 76-year-old woman know how long she will live? How do we know?

A 75-year-old man has an average life expectancy of 12 years. But when Dr. Eric Widera, a geriatrician at the University of Califo...