Supercentenarians are making headlines, and people are trying to adjust their lives in an attempt to live longer and healthier - but what really determines one’s life span? Is changing your lifestyle sufficient to increase longevity or is it engraved in your DNA? The short answer is both, your life choices and genetic background, are the defining causes of your life expectancy. But let’s dive deeper into each category.
The genetics of ageing
For a very long time, people have believed that ageing was genetically programmed and thus the process was seen as a natural continuation of a life cycle. This idea has long been abandoned, and a conventional (and acceptable) view of ageing today is that of the process in which a living organism wears out due to the deterioration of the repair mechanisms. While this is partly true, the ability of the human body to survive in the most extreme situations suggests that our organisms are way stronger than we think. If that’s the case, longevity should be the norm thanks to a family of genes responsible for activating the repairing mechanisms in stressful environments [1]. Well, things might be more complicated than that, but genes definitely play a pivotal part in determining one’s life span.
The studies by Tom Johnson, a pioneer researcher in the field of genetics of ageing, have been among the first to demonstrate the correlation between ageing and genetics. His first studies were concentrated on roundworms, where he separated long-living individuals from short-living individuals. The analysis of hybrids obtained from different strains of roundworms (C. Elegans) allowed him to estimate that the heritability of their life span was between 20 and 50% [2]. There have been done numerous studies and advances in the field since then, which allowed a broader understanding of how these genes work in humans. Today it is estimated that around 25% of human longevity factors are determined by genetics. Not by chance, it’s said that a longer life span runs in families, with children and siblings of long-living individuals also expected to live longer. The variations of several genes are believed to be responsible for how long a person might live, with some variations commonly found in the APOE, FOXO3 and CETP genes. What’s interesting is that these variations are not necessarily present in all long-living individuals. This fact suggests even more variations in multiple genes, some of which are still unidentified, could be associated with long life [3]. So while delayed ageing and a longer life span might be partly dictated by our DNA, our organisms are much more complex than that - and one should take into account genetic inclinations to certain illnesses, other gene variations and potential mutations, lifestyle and the environmental factors. DNA tests and genome sequencing are a great way to find out your predisposition to living longer as well as the potential diseases you may develop, so you can take timely action to prevent them. However, it’s important to remember that an increased life span does not always equal a healthier life.
Life expectancy at birth has been progressively increasing over the past century in the Western world, thanks to the advances in medical assistance, reduction of infectious diseases, improvement of the environment (free and unlimited access to clean, safe water and food), better housing and living conditions - you name it. Infant and child mortality rates are lower than they have ever been, but fighting the diseases common for older people, like cancer or Type 2 diabetes, as well as developing patient-sustaining treatments, have contributed greatly to the increased life span today. This leads us to reconsider the question of longevity and talk about ageing in terms of successful ageing.
Human longevity and lifestyle
Long-living individuals might not necessarily have the same gene variations, but most of them share similar habits and lifestyles: many of them are non-smokers, have a rather healthy weight, and are (and have mostly been) coping well with stress. You read it right - stress is known as one of the most influential factors in premature ageing. Chronic stress increases the risk of depression, anxiety disorders, heart diseases and high blood pressure - all of which contribute to reducing the average life span by about 2 years in both men and women [4]. Smoking might seem like an obvious obstacle on one’s way towards a longer, healthier life, but this is a persistent habit that for many is hard to quit - and yet, quitting smoking before the age of 40 has been found to reduce the risk of dying from any smoking-related disease by 90% [5]. The same goes for exercising, cutting down on alcohol and getting enough sleep - there’s no need to go to any extremes, but following the general rules of a healthy lifestyle might actually bring you the very tangible benefits in form of being healthy and autonomous long into your elderly years.
Another important correlation between lifestyle and longevity is closely linked to one’s diet. Dietary restriction can trigger a molecular-genetic response which postpones ageing and age-related phenotypes. Not by chance, some geographic areas characterised by exceptional longevity (such as Sardinia and Calabria regions in Italy) are renowned for their ipoproteic diets, like the famous Mediterranean diet [6]. This traditional diet stimulates the molecular mechanisms which can increase the life span. Mediterranean diet is not the only healthy one (although it has long been considered an absolute winner among lifestyle diets [7]); other healthy choices might include a flexitarian or DASH diet. As a general rule of thumb, a healthy diet should focus on the intake of fruits, vegetables and whole grains. The Mediterranean diet also favours legumes and olive oil, as well as fish and poultry as sources of lean protein. Red meat is usually reduced due to its correlation to negative effects on your body, such as an increased risk of developing type 2 diabetes, coronary heart disease and even certain types of cancer - but it doesn’t mean these diets should be plain. In fact, the traditional Mediterranean diet even features moderate consumption of red wine (when there are no medical contraindications). This kind of diet might not only postpone ageing, but also reduce the cardiovascular diseases risk [8], lower body mass index [9], and even reduce the brain’s age by five years [10]. Choosing the diet that’s right for your body is an important step towards longer life, and taking informed decisions about how you nurture your body should always be a priority.
One more very important factor that is closely associated with how our lifestyle impacts our quality of life and ageing is oxidative stress. We should take a step back to consider what ageing actually is: a process characterised by the progressive loss of tissue and organ function. Now, our body is a complex mechanism, and it produces chemically-reactive molecules containing oxygen and nitrogen. Reactive oxygen and nitrogen species (collectively known as RONS or free radicals) are produced by several processes in our body and may have some negative effect on its overall functioning - unless those are neutralised by antioxidant defences. Oxidative stress occurs when there’s an imbalance between RONS production and the antioxidant defences to counterbalance it. The oxidative stress theory of ageing is based on the hypothesis that ageing (and thus the loss of certain functions) is induced by the accumulation of the damage caused by RONS. While this is only a hypothesis, there’s also clear evidence that oxidative stress is involved in the development of several age-related conditions, such as cancer, cardiovascular and neurodegenerative diseases [11]. Moreover, the general idea of how our lifestyle influences ageing is easily observable through an example of this process - it demonstrates clearly what’s going on in our bodies at all stages of life. Oxidative stress occurs naturally, although there are several factors contributing to free radical production, such as diet, habits and environmental conditions (like pollution and radiation). Since this is a natural process, we can’t really fight it, but we can ensure we have enough antioxidants to balance it out by following a healthy lifestyle [12].
Now that we’ve established that your lifestyle is as crucial as your genes, let’s not forget that scientists are working non-stop trying to unlock the secrets of longevity genes and other factors that will allow our society to go from treating age-related illnesses to preventing them in the first place. And while we’re not quite there yet, you can already take action to ensure a longer and healthier life. Staying informed about how your lifestyle affects your overall health and being aware of your genetic predisposition to certain diseases is the first step to gaining control over your own life and postponing ageing.
