At the Dusk of Life: Signs of Body Ageing
Many of us have said that age is just a number at least once in our lifetime. Still, the older we become, the more often we think about how much this number will continue to grow. We also wonder how long our feeling of being young will correlate with our appearance and physical abilities. Or, putting it more simply, when we start to be old? And if being old is not about age, what does being old mean?
In its recent classification, the World Health Organization has prolonged the age of youth to 45. People between 45 and 60 are considered middle-aged, those aged 60-75 are senior citizens, and people over 75 are considered elderly. But as with most approximations, this classification has nothing to say about each person. All of us know at least one young “old man” who starts to complain about life at 30 and dreams about retirement at 50, and at least one vibrant personality over 80 who is more active than friends of his or her children.
So what influences aging? When does it start? How can we define a moment when life begins to slow down, and what can we do about it? And finally, can science tell us how long we will live?
How do we measure aging?
For many centuries, scientists have searched for the markers of biological aging, which could tell us more precisely the state of our body and predict when this body starts to age. Different cultures at different times had various standards for defining people as old, such as losing fertility, critical deterioration of senses, gray hair, and others.
Today, there are three accepted criteria as markers of aging suggested by the American Federation for Ageing Research in the report titled “Biological Age Predictors.” These criteria include the ease of measurement (provided that the process of measurement should not accelerate the aging itself), the ability of the marker to assess the risk of death, the relation to the biological aging processes, and the ability to use the marker for humans as well as for animals. These criteria are pretty strict, and only three markers could meet all of them during the last 16 years after the requirements have been accepted. We will describe them in more detail below.
The first marker: Frailty Index
The frailty index is based on the list of symptoms that can be frequently seen in humans or animals and which can have a very harmful health impact. The most recent list of symptoms, titled “A Frailty Index for UK Biobank Participants,” was published in 2018 and is available to anyone interested in checking one’s health. It is enough just to add one point for each present symptom and evaluate the final result, which could help predict the need for regular care or even chances of death from aging.
However, this method works only for aging adults. Younger people haven’t lived enough to develop chronic and dangerous illnesses, so their results would not be valid.In 2015, researchers from the National Academy of Science of the USA offered their list of markers, titled “Quantification of biological aging in young adults, “ not directly related to chronic or dangerous diseases. This list includes, among others, cholesterol levels, body mass index, Hb level, mucous membrane condition, and other signs which can be examined at any age. The test result allows for evaluating the body age, which often doesn’t match the actual age. Thus, the body age of those research participants, who were 38 years old, varied from 30 to 50 years.
The second marker: the length of telomeres
The telomeres are the ends of DNA that shrink each time a cell divides. When the length of telomeres becomes critically short, the cell loses its ability to divide, and aging starts to occur. On average, the length of telomeres allows 50 cell divisions, and for a long time, this parameter was considered decisive in determining the lifespan of our bodies.
But later studies have challenged this idea. First of all, it has turned out that the length of telomeres can vary significantly depending on many factors. Thus, on average, women’s telomeres are longer than men’s, as evidenced by the research titled “Reflections on telomere dynamics and aging-related diseases in humans.” Meanwhile, the telomeres of children of older fathers are longer than those of children whose father was young at the moment of conception, as shown in another study “Older paternal ages and grandpaternal ages at conception predict longer telomeres in human descendants.“ Finally, in some countries, people have different lengths of telomeres in dry and rainy seasons, as can be seen from the report “The telomere lengthening conundrum – it could be biology.”
Moreover, there are cases when telomeres have increased in length in people after the age of 75, as evidenced by the research “Human telomere biology: A contributory and interactive factor in aging, disease risks, and protection,” or in those who spend a year in orbit as can be seen from the research “The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight.”
Despite the seemingly simplistic and plausible criterion, it looks like it cannot be relied upon entirely. In most cases, telomeres’ length correlates with the life span, but scientists are not yet certain about it.
The third marker: methylation clocks
As we grow older, we change together with our DNA: the longer we live, the more densely DNA threads are recoiled inside the cell nucleus. During this process, some parts are contracted, and information recorded with them becomes non-accessible while others open up, providing previously unavailable data. This curtailing is affected by the so-called methyl groups, and the more numerous they are, the more intense the process is.In 2013, in his research titled “DNA methylation age of human tissues and cell types,” the American scientist Steve Horvath offered the so-called methylation clocks consisting of 353 parts of DNA, some of which obtain a methyl group during the lifetime while others lose it. These clocks are made on the basis of the study “DNA methylation-based measures of biological age: meta-analysis predicting time to death“ and are based on allocating those parts of the DNA, which are subjected to methylation and are capable of telling us the lifespan of the human being as well as even the lifespan of individual cells. Yet, one problem remains as we still don’t know why some parts of DNA have a key role in aging and, most importantly, how we can influence them.
Is the dusk coming down?
Science aside, each of us knows pretty well what aging means as our bodies lose their physical functions and ability to withstand illnesses. There are certain signs which can help us to understand when it is time to pay more attention to our health, and here are some of them:
- Your hands become weak
The strength of your handshake and even the ability to open a jar of preserves can be a sign of your body age. The research published in The Lancet magazine, titled “Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology,“ has confirmed that people with weaker handshakes have a 16% higher risk of death from various reasons. It all depends on the muscle mass, which is actively lost with age, and if we don’t withstand this process, we start aging earlier and more rapidly. But there is good news: those research participants who developed their grip strength lived longer.
- You get more fat around your waist
All of us gain weight as we get older, but if it concentrates around our waist as it goes with the men, we are in trouble. The research done in 2019 has supported the thesis that those women who had extra weight on their bellies were twice more prone to dangerous heart diseases than women who accumulated fat around their thighs.
- You are a slow walker
The way we walk is directly related not only to physical but also to mental health. This was concluded by the authors of research in New Zealand “Association of Neurocognitive and Physical Function With Gait Speed in Midlife“ participated by 900 volunteers. The results of the study have shown that those participants of the research whose gait speed was lower than average had worse physical health, their body age estimate was higher, and the scope of their hippocampus (the part of the brain responsible for memory and cognitive abilities) was smaller than those of faster participants of the experiment.
Meanwhile, the research “Self-rated walking pace and all-cause, cardiovascular disease and cancer mortality: individual participant pooled analysis of 50 225 walkers from 11 population British cohorts” conducted in 2018 and published in the British Journal of Medicine has demonstrated that with speed around 6 km/hour have lowered the risk of death from all causes for 20% (and even more for patients aged over 60).
- You have frequent bone fractures
Fragile bones are another sign of getting older. After 40, we begin to lose calcium, which becomes more intense each year. Moreover, each year our cells are less capable of storing vitamin D, which is essential for our bones, and as a result, we are more likely to get injuries and fractures.
- Our face proportions change
There is another substance we have less as we get older, which is collagen, which creates a protective network for our skin cells. The less collagen we have, the faster our skin deteriorates, and the sooner our face shape changes (first of all, the lines of our cheeks). Besides, our jawline also changes with age (due to cartilage wear and teeth loss or changes), which also impacts our face proportions.
So is age not just a number?
Whatever the date of birth in your ID and the number of candles on your birthday cake, these have minimal effect on the state of your health, expected lifespan, and even your actual age. According to statistics, most of us are likely to live up to 75 and get one or more chronic diseases when we reach 65. Meanwhile, we are not just statistics. Indeed, our actions and habits (first of all, our life-changing habits as well as eating and health-care habits) determine how young we will feel every year and, finally, how long we will live.
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