How it feels to be on the brink of a life passage, from youth to middle age to death.

How Old Are You Really?

Lifelong planning might be easier if you knew the tempo of your biological aging

People love those self-tests that help them calculate their biological (as opposed to chronological) age, especially if they feel younger and healthier than their peers -- how cool, they think, if a measurement would give them objective proof of just how youthy they REALLY are. It's no surprise that the RealAge quiz has become the most popular self-test on the web (despite the fact that it has 150 questions). So a report in The New York Times about the search for biomarkers of aging should be interesting to lots of people curious about their true biological age -- and, as a corollary, projections they might be able to make about the tempo of the rest of their lives.

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The items used in an evidence-based self-test for biological age are somewhat surprising, and certainly different from the self-tests you's see in a typical women's magazine. For instance: gerontologist Richard A. Miller of the University of Michigan found that one of the most revealing measurements of a person's rate of aging was his or her contrast sensitivity, the ability to distinguish very faint images on a white background. In 2010, Miller developed a set of 13 factors like this that are most likely to predict death from various causes (another, grimmer way of looking at the concept of "healthy aging"), based on an analysis of more than 4,000 women collected over 20 years, beginning when the women were in their 60s.

The goal, as Miller put it to Times reporter David Stipp in the recent article, is to find a group of biomarkers that accurately predict not only how long an individual is likely to live, but how well. As he put it:

“Do those 50-year-olds with the best retention of immune function also tend to have the least cataracts, good sense of smell, least osteoporosis, lowest blood pressure and best memory?”

Many of the items on Miller's 13-item Healthy Aging Phenotype checklist were the ones you'd expect -- negative points for smoking or diabetes, positive points for self-reports of good health. But there were a few that were less expected, like that measurement of contrast sensitivity. 

The next step in generating a truly accurate picture of biological age is by turning to genetics, which is what  scientists at the University of California, San Diego have been doing. They found 71 identifying markers on genes, known as epigenetic tags, that can predict the rate of aging at a cellular level. Te goal is to determine the rate at which these tags change from one age to another, which might allow them to say whether an individual is aging at a rate that's faster or slower than the norm, another step on the way to developing a biological age.

Stipp reflected on where we might be headed if research led to effective tests that could accurately predict one's rate of aging: 

Insurers might demand that customers take them in order to set premiums for life and health care policies. The tests may also reveal how factors like exposure to environmental toxins and the stress of job loss accelerate aging, and by how much — fodder for lawsuits.

Some of us will be relatively short-lived, fast-aging “less fortunate,” and others will be long-lived, slow-aging “more fortunates,” predicted John K. Davis, a philosophy professor at California State University, Fullerton. And age discrimination will gain an entirely new meaning.

Some time in the not-too-distant future, we might be able to know, even in our 20s, the biological fate that lies ahead. If this happened, maybe people on the cusp of adulthood would make decisions about pacing (how quickly to finish school, choose a career, start a family) that are attuned to rate at which the rest of their lives might actually unspool. It will be interesting whether young people would even seek out such information if it were out there, and how many would decide that they'd just as soon not know.



Robin Marantz Henig is a science journalist and co-author, with her daughter Samantha Henig, of Twentysomething: Why Do Young Adults Seem Stuck?


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