Preconceptions, what are known as “biases”, can be insidious, in the sense that it is easy to fall victim to them without even realizing it. Who has never jumped to a hasty conclusion in an attempt to find a correlation between two variables that seem to influence each other in some way? Seem, but perhaps they have no effect on each other at all. Or perhaps they do, but before the link is solidly demonstrated, years and years of scientific research may be needed. But what does all this have to do with the aging process and the concept of longevity? It has everything to do with it, as Bradley Elliott, researcher and lecturer in physiology at the University of Westminster (United Kingdom), explains in an article he wrote for The Conversation.
Which is the cause and which is the effect?
Elliott’s research is precisely in the field of the biology of aging, seeking in particular to understand the processes that cause the loss of muscle mass typically seen with advancing age (sarcopeniaThe term sarcopenia refers to the progressive loss of muscle mass and related decrease in strength; in addition to the volume reduction in muscle mass, it also leads to a worsening of the latter because:
• the muscle is slowly replaced by adipose tissue (fat),
• the junctions between muscle and nerve fibres (neuromuscular junction) tend to degenerate,
• muscle oxidative stress increases.
). One of his research projects, for example, focuses on the study of people over the age of 65 who have managed to maintain a level of activity and physical fitness well above the average of their peers.
Now, the question, Elliott explains in the article published in The Conversation, is the following: did being active and fit allow these individuals to enjoy good health for a long time, or, on the contrary, was it the fact that they did not develop particular diseases that allowed them to stay active even beyond the age of 65?
Of course, regular physical activity is one of the factors that contribute to healthy aging; this concept is now widely accepted. But if the goal is to answer a specific question like the one just formulated, which concerns not a generic situation but a group of individuals with certain characteristics, things are not as simple as they may appear. And there are no shortcuts: reaching solid conclusions requires data, analysis, comparison… and a lot of time.
Elliott’s study is, in fact, ongoing, but the general message is clear: deducing which lifestyle is the healthiest from the habits of a single centenarian is wrong by definition. The only way to tackle the problem is to consider a statistically significant sample, that is, to refer to knowledge that has been confirmed over time and that comes from studies that are as comprehensive as possible.
Watch out for “survivorship bias”
There is also a specific preconception that Elliott discusses in the article: it is called “survivorship bias”, or survival bias. Once again, this has to do with the eagerness to reach conclusions that are too easy to be true. Of course, there may be centenarians who have led bizarre lifestyles incompatible with the knowledge accumulated over centuries of scientific research, but this does not mean that those lifestyles should be followed for healthy aging. Why? Simple: because we can only talk to those who have survived. And for any example of lifestyle, whether more or less healthy, there will be a share of the population that did not reach 100 years of age, or did not even reach 90, 80 or 70, and that therefore will not be able to advise us against eating fried foods for lunch and dinner every day.
