Why We Age

What does it mean to be youthful? To live long? To live and work productively? The question is so loaded that each individual may offer a different answer – at different times of day. But doctors have their own metrics, and lifespan is one favored endpoint. They want to know how stuff they can measure – like fats in the blood or cognitive abilities – track out in predicting lifespan and “healthiness.” And some of the answers are surprising.

Two recent studies – in the US and New Zealand (though much of the latter’s data analysis was performed in the US) argue that people – young and old – age at very, very different rates – and that lifestyle, particularly physical activity, hugely changes the results. In other words, certain behaviors lead to lots more “youthful” looking regeneration than others.

The Dunedin Study

Trying to “quantify biological aging in young adults” a recent version of the Dunedin study – watching over a 1,000 New Zealands since birth in 1972-73 – used a “biomarkers” approach. In part pioneered in the US by the National Health and Nutrition Study (NHANES) the New Zealand group looked at 18 biomarkers like waist-hip ratio and total cholesterol to determine who was youthful and who was not. They asked a group of Duke students to classify the faces of the people – and found the biomarkers fairly well predicted who looked younger and who did not. Some other results were more interesting:

1. The relative level of youthfulness varied over 3 decades. Some people were classified by their algorithms at “biologically” aged 28, while others were “biologically” in their sixties – though everyone was actually the same chronological age of 38.
2. Some people were able to “negatively age” – on followup they looked younger with the passing years.
3. A few folks were aging rapidly – going up three years in biological age for every year lived.

These results are consistent with other studies, including a recent American survey of Senior “Olympians.” People who are competitive athletic at the age of 50 and beyond should be expected to be in good shape.

But they also look younger in terms of different biomarkers. In this study, well reported by Gretchen Reynolds in the NY Times, many of the Olympians were “biologically” 20-25 years younger than their chronologic age.

So what does all this mean for you?

Biological Versus Chronological Age

There are many aspects of aging, which indeed occurs at very different rates in different people – and in the same person. Stressful events do indeed age people “overnight.” People stranded at sea may survive starvation and return looking and feeling decades older. Hair can turn white overnight. Some forms of stress, including torture and extreme anger, can cause heart attacks, strokes, and instant death.

So biological age may not always be a good predictor of how long you will live.

This appears true of some of the recent biomarker approaches. Based as they are on correlations, some of the relationships between variables can be “gamed” by commercial sites. The site “Real Age,” for example, found that those who had sex twice a day had a “biological age” 17 years younger than otherwise expected.

Does that mean having sex twice a day will cause you to live 17 years longer than otherwise expected? Some may wish to try this out in their own lives, but I suspect the results – at least in terms of overall lifespan – may be rather disappointing.

But biological age does tell you important things. It not only predicts (a bit) how long people will live, but can tell you a lot about stuff people care about – including how they look, how they feel, and how mentally and physically capable they are.

Getting Younger

In the age of Big Data, lots of information gets processed. Algorithms predicting who will be a future felon and who will be a future centenarian will be hypothesized, examined and statistically modeled. Tracking the results with real people over time will eventually provide better ideas of what can and cannot be predicted for human populations.

But more variables needs to be looked at than lifespan. Measures of mental health need to be included, and not just whether someone is depressed or cognitively impaired. Positive aspects of life like satisfaction and gratitude, many of the components of the Positive Psychology Movement, need to be tracked. So also will measures of social health beyond how many friends and acquaintances one has, and spiritual health, with measures more useful than amount of  church attendance.

For health is a bigger picture than lifespan or even “quality life years.” And people are living longer. American adults at the time of Social Security’s enactment could expect lifespans almost twenty years less than today.

We’re living longer. Now the trick is to see what actions we can take that will make those years “healthier.” Exercise is clearly part of the picture, but there’s much more to be learned.

Particularly on how to really enjoy the ride.