Lifespan calculators add up to puzzling results
It seemed to be as good a way as any to start researching an article on predicting lifespan. I asked Google, “How long will I live?” It offered me some calculators. Thefunbegan. Even before I started calculating, I had concluded I should plan for a long life. My mother is still alive at 89. My father, a lifelong, heavy smoker, made it to 84. I’ve got a lot of positive risk factors: female, college education, healthy weight, exercise most days, plant-heavy diet, no chronic health conditions plus good cholesterol and blood pressure numbers. (I’m a health writer. I take this stuff seriously.) I started playing with the calculators. The easiest one was from the Social Security Administration. It’s based purely on averages, and said an average woman my age — 63 — would live to 86.5. This was not terribly helpful as I’m not average. I also tried calculations for a medical train wreck of an age peer. She was the height and weight of an average American woman — 5 foot 4 and 168.5 pounds. (That’s a BMI of 29. Thirty is considered obese.) She smoked, but less than two packs a day, and had diabetes and family history of heart disease, barely exercised, ate a pretty typical American diet, was a heavy drinker, didn’t finish college, slept poorly and stressed out. I tried a calculator from Northwestern Mutual. It said I’ld live to 102. Yikes! I’ll be out of money long before that, I thought. My alter ego would be gone at 66. MetLife’s simple calculator said I’d live to 90, with a 25 percent chance of living beyond 97. My alter ego would live to 76 or 80. The Living to 100 calculator said I’d live to 97 and offered investment opportunities. That one asked fairly detailed questions about diet and stress. Then I found one designed at the University of Pennsylvania. I talked to Lyle Ungar, a professor of computer and information science, who helped create it. Any good calculator, he said, has to tell you about your odds of reaching a certain number. That one predicted my life expectancy as 96. I had a 75 percent chance of making it to 88 and a 25 percent of surviving to 101. Next came ePrognosis, designed to help doctors make medical decisions, such as whether it’s still worthwhile to do screening procedures like colonoscopies. This calculator asks more questions than others about daily activities, such as walking a few blocks or paying bills. It expresses your odds in terms of how likely you are to die in up to 14 years. The calculator said I had only a 3 percent to 6 percent chance of dying in five years, but the range rose to 19 percent to 24 percent by 14 years. Last, I talked to Jay Olshansky on the recommendation of the American Federation for Aging research. A professor in the School of Public Health at the University of Illinois at Chicago, he helped develop an estimator that is now available to life insurance companies and will soon be used by financial services companies to help people plan for retirement. The problem with most lifespan calculators, he said, is that they use an “additive” model. That means they start with the average expected lifespan and add or subtract years based on behaviors — which I saw as I used the Northwestern Mutual calculator, which said I’d live to the unlikely 102. This doesn’t work well because behaviors tend to travel together, he said. “If you’re highly educated and physically active,” he said, “it’s hard to smoke.” He walked me through the survey, which asked many of the same questions as the others, but weighted the answers differently. The results: My expected lifespan was 87.4 years, and I’m likely to be healthy until I’m 82.3. My alter ego made it to 82, with only about a year of disability at the end. I was a little disappointed with my numbers after the other calculators. Hopefully, I won’t know whether any of the calculators were right for at least a couple of decades.