Slowing Age-Related Decline

“No other animal passes so large a portion of its existence in a state of absolute helplessness, or falls in old age into such protracted and lamentable imbecility.”
—John Herschel, 1830

Humans, perhaps uniquely among the creatures on this planet, can travel mentally in time and imagine their remote future lives. The prospect of suffering the “lamentable imbecility” of old age that John Herschel noted is a particularly unwelcome prospect, and therefore acts as a powerful driver for a vast industry promoting potions, programs, and pointers aimed at halting or slowing age-related decline.

Some evidence suggests that the attitudes people hold about their own aging may influence the trajectory of future losses of cognitive function, pointing to new potential avenues for protecting future well-being. Could some kind of public awareness campaign or psychotherapy push us to adopt better attitudes that will in turn increase our chances of happiness and well-being in old age? This is an appealing (and for some, a potentially lucrative) vision.

But we need to be cautious not to mistake correlation for causation. There are alternative explanations. People with positive attitudes about aging may simply be the ones who indeed have reason to be positive because their relatives lived long, healthy lives and their own underlying health is robust. In that case, changing someone’s attitudes may bring about unrealistic expectations, rather than any desired effects on age-related change.

Decline is as inevitable as death. Many of us think of life as comprising essentially three main stages: growing up, the normal adult life with full command of our powers, and the dreaded decline in old age. In reality, we are constantly changing. Our categorical labels hide a much more dynamic ongoing process.

Diverse capacities peak at different times. Consider elite athletes. Professional football players may be at their best between the ages of 25 and 30. This is a rather short period, given how many years of committed training brought about improvement, and how many more years they may play with gradually decreasing capacities. One would be well advised to try to enjoy the journey, as the top performance level may be disappointingly fleeting. There are, of course, large individual differences in the peak performance and the speed of decline. What should be clear, though, is that capacities do not remain unchanged.

As it is with athleticism and muscles, so it is with our minds and brains. Our brains grow gradually with age, reaching their full size before puberty. Throughout adolescence, cortical white matter increases and grey matter becomes thinner, reflecting ongoing pruning of synapses and the myelinization of axons. This late maturation is evident even in the most basic aspects of cognition. Performance on the simplest executive control tasks improves throughout adolescence.

It may come as a surprise to learn that certain aspects of brain development are not complete until much later. The uncinate fasciculus, a white-matter tract linking the orbitofrontal cortex, amygdala, and temporal regions that is implicated in socio-emotional processing, only reaches full maturity during the mid-30s. It then declines. Change is constant.

In cognitive capacities, as in athletic capacities, many of us would like to buffer the deterioration and are willing to expend considerable time and money combating the rot. Researchers too may be willing to invest considerable effort. And they may be disinclined to accept evidence suggesting that certain declines cannot be ameliorated.

When we learn, for instance, that being bilingual may protect against decline and delay the onset of dementia, we take note. We may subsequently promote the learning of a second language, be more inclined to look for evidence supporting the power of such learning, and would be reluctant to accept anything to suggest otherwise (a meta-analysis of prospective studies, it should be noted, sadly does not support the effect)—particularly when we have already made a big effort.

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This may reflect our tendency to engage in self-deception. Self-deception produces a biased view of the world, and so as scientists, we ought to safeguard against it. From an individual’s perspective, some systematic bias may be a healthy strategy. It may even have evolved because it benefits us. Our tendency to exaggerate the emotional impact of future events may be important in driving us to avoid future harm and secure future rewards.

Being realistic may not always be as useful and desirable as it sounds. It turns out that mildly depressed people tend to be quite accurate in their predictions compared to the rest of us, who mostly tend to demonstrate an optimism bias—a bias that may, in fact, be very useful. “Optimism,” Noam Chomsky is said to have remarked, “is a strategy for making a better future. Because unless you believe that the future can be better, you are unlikely to step up and take responsibility for making it so.”

A version of this post was published in inference as a commentary on a review essay: titled "An Old Infirmity."