If you want to know how well you are going to age, look to your lungs. The latest medical wisdom is that, of all measured body performances, lung function is the best predictor of longevity.
A man’s ability to get oxygen into his body – to breathe fast and deeply-will predict how long, in the absence of disease, he is likely to live. Fortunately people are equipped with much more lung function than they need. When humans were designed millions of years ago they needed a lot of lung capacity to survive – to hunt and to escape predators. But today, with modern lifestyles, they use only a small amount of their lung capacity. The rest is kept in reserve and drawn on during exertion or illness.
This reserve sustains people into old age. Although humans’ lung function usually peaks in their early 30s, older people are still sufficiently endowed for excellent performance because they can draw on this great reserve.
World records for marathon running show that times increase by a minute a year after the age of 30 or 31. The best time for a 70-year-old is about 40 minutes longer than the best for a 30-year-old. But that is still pretty impressive. It indicates that if a 70-year-old man is in excellent health, his age-related impairment will still allow him to run a marathon in under 3 hours.
As most men approach 70, however, they accumulate illnesses that affect their lung function and make them more vulnerable to disease insults, which, in turn, impede overall performance. As people age, their ability to oxygenate their blood declines measurably. This is not only because breathing is less deep and, as a result, less oxygen enters the lungs, but also because less of the oxygen in the lungs actually gets through the lung tissue and into the bloodstream.
The task of the rib cage and muscles is to pull the lungs out and keep them full of air. But the lung tissue itself is constantly trying to do the opposite and make the lungs collapse. Over-expansion or too much collapse can be harmful to lung performance.
The lungs are like balloons. As such, a major problem with them is that they become less elastic as they age, losing their recoil capacity. When this happens, people often develop expanded, or barrel, chests because the chest wall is increasingly able to expand unchecked by the counterforce.
When elastic stretch is lost in the lower parts of the lung, the little air tubes inside the lower lung collapse and air that is breathed in can’t get into them. Blood still travels around the lower lung trying to gather oxygen, but fails.
Lung function is largely genetically determined and, in general, tall people have better lung mechanics because there is less squashing of the abdominal contents, allowing the diaphragm – the breathing muscle – to work better.
Living in a nonindustrial setting and refraining from smoking both help to sustain good lung function. Maintaining an aerobic exercise pattern also helps, as does good posture and good abdominal, shoulder and neck muscle strength. Long-term playing of a musical instrument that demands lung power may also help.
Because much of the lung decline that accompanies ageing is invisible, an X-ray of an 80-year-old’s lung may look no different from that of a 30-year-old. But special stains that highlight elastic tissue would show dramatic anatomical changes.
Much of ageing is due to changes inside the tissues: reserve capacity inside the cells declines, and if there is an attack or insult on older tissue, function can be dramatically impaired. If a radiologist looks at X-rays of a 30-year-old and a 70-year-old with pneumonia covering 10 per cent of one lung, both pictures will look the same. The difference will be that the younger patient will be sitting in a chair, impatient about the delay and ready to go home, while the older patient will be lying on a stretcher, on oxygen, gasping for breath.
In older healthy people, declining reserve capacity does not interfere with day-to-day functioning. But when an illness is introduced, it can move them rapidly from feeling fine to feeling ghastly. It is characteristic of older people that they can be great one day and very ill the next.
The only way to check your lung function is to have a formal test. These tests have age- and sex-adjusted standards.
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