How old are you really?

For a simple number, age has a powerful grip on our lives. It tells us when we can start to drive, when to embark on a career, when we should get married and then when it is time to go gracefully into retirement. Some scientists, however, believe the time is right to loosen age’s stranglehold. A small but growing band of researchers think that age should be replaced by other metrics that better reflect our physical and mental well-being.

Susan Krauss Whitbourne, a psychologist the University of Massachusetts Amherst, points out that chronological age simply reflects the number of revolutions of the Earth around the Sun since we were born. But the extent to which mind and body evolve during that time varies hugely from person to person. Whitbourne notes, for example, that a sprightly 60-year-old can be in better shape physically than a sedentary 25-year-old. “If they had to run for a bus, the older person would beat the couch potato every time,” she says.

Warren Sanderson also believes society has become too fixated on chronological age. An economist at the International Institute for Applied Systems Analysis in Austria and Stony Brook University in the U.S., Sanderson argues that people should instead be described in terms of functioning. In other words, whether someone has the physical and mental capacity to lead a productive life – an absence of serious illness, for example, or the ability to use computers. In particular, he says, “it makes no sense to call people old just because they reach 65”.

Functioning can be broken down into a number of dimensions. One of these is life expectancy, which can be expressed through prospective age: how much younger people have in effect become relative to some benchmark year. So, for example, someone who is 65 today would have a prospective age of 60 if they share the life expectancy of a typical 60 year-old from 2000. “It is like saying that 40 is the new 30,” quips Sanderson, who carries out his research with demographer Sergei Scherbov.

How people move

Another dimension is biological age, a complex notion that sums the state of all of the many and varied systems within the human body. Simon Melov, a biochemist at the Buck Institute for Research on Aging in California notes that experienced doctors can estimate this in just a few minutes, based on simple indicators such as a person’s appearance, how they move and how quickly they are able to stand up. Such an assessment is of course subjective. Science, in contrast, strives for objectivity. Ideally, says Melov, what is needed is a single parameter than can be quickly, easily and unambiguously measured – like a person’s blood pressure. That could be very handy not just for assessing healthy people but also as a marker in the development and administration of new drugs designed to reverse age-related illnesses.

Melov and other scientists have tried to find a genetic marker for this purpose, but so far without success. As things stand, he says, the best metric is in fact decidedly low-tech. That metric is walking speed. Individuals who stride at more than about a metre per second, he explains, tend to be healthier than those who get about more slowly.

Another good predictor of someone’s health is the body’s ability to absorb oxygen while at peak physical performance. Defined by a quantity known as VO2 max, this is usually measured by pushing people to exhaustion on a treadmill or an exercise bike. However, Ulrik Wisløff and colleagues at the Norwegian University of Science and Technology in Trondheim Norwegian have shown it can be accurately estimated using just five, easy-to-obtain pieces of data: age, sex, waist size and resting heart rate, as well as how often and how strenuously someone exercises. Analysing 37,000 men and women aged 20 and above in mid-Norway, the researchers found that this paper-based metric could accurately predict which people were at lowest risk of heart attacks and other premature death.

Learning and remembering

VO2 max and walking pace measure what is known as fitness age. This provides a pretty good estimate of someone’s overall health because higher values require the proper functioning of multiple organs, including the heart, lungs and also brain. But, as Melov points out, it doesn’t quite tell us everything about our biological well-being. It doesn’t, for example, reveal anything about the functioning of our kidneys.

Another dimension that determines a person’s functioning is psychological age. This breaks down into two components, one of which is cognitive, in other words how well we can learn and remember. This is similar to what is known as mental age, a term usually associated with children and originally measured in terms of IQ. The other element relates to emotions. In other words, how well a person can defer gratification, control their temper, cope with negative situations and deal with difficult people. As Whitbourne points out, such things are harder to measure than either physiological parameters or cognitive parameters such as memory. But she says it is vital to understanding age, noting that being able to control our emotions is one of the few things that we actually get better at as we age. As she puts it, “older people are truly wiser”.

Finally, there is social age. This is determined by social norms regarding when certain key events in your life ought to happen. Your social age will equal your chronological age, for example, if you get married and have children in your early- to mid-30s. But you will have a lower social age if you do these things later on – 10 years lower if you were to delay them until your 40s. Conversely, if,as a high-performance athlete or lottery winner you retired at 25, then your social age would skyrocket by 40 years.

How do you feel?

Scientists hope to be able to reduce the number of different ages to as few as possible – if not to a single parameter – in order to easily and confidently assess both the quantity and quality of life available to any individual. But disappointingly, or reassuringly (depending on your point of view), for the moment perhaps the best measure of someone’s true age remains the subjective one: how old you feel. According to Whitbourne, true age can be pretty reliably gauged by asking someone how they feel several times over the course of a few days and then taking a kind of average. This, she says, allows that person to take stock of what is going on inside them both physically and mentally.

Reining in that age means looking after both your physical and mental health. Exercise, Whitbourne points out, can arrest and even reverse ageing of body and mind, the latter thanks to higher oxygen levels in the brain. However, the right attitude is also vital. In particular, she says, older people should avoid automatically blaming temporary memory loss on the brain’s decline and instead ask whether it could be due to stress, anxiety or even the worry of getting older. “There is so much ageism, especially in Western culture,” she says, “that people feel old and so they become old”.

The solution: get that positive thinking cap on and head down to the gym. Then watch as the pounds, and the years, drop off.



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