Are we really living longer?
Author: Prof. Zbigniew Gaciong a specialist in internal medicine and hypertension from the Department of Internal Medicine, Hypertension and Vascular Diseases of the Medical University of Warsaw.
It is estimated that during the Paleolithic era, people lived an average of 30 years and worked only 5 hours per week. This was enough to gather food or hunt a large animal, which was a source of food for the entire tribe for many days. Today people both work and live much longer. Analyzing the oldest Anglo-Saxon censuses, it can be seen how life expectancy increased in successive centuries. However, the most rapid growth has occurred in the last century. First and foremost, it has to do with the reduction in infant mortality achieved through immunizations, newborn care, perinatal care, improved hygiene, and increased affluence.
Calculated subsistence level
To answer the question of how many years a person can live, it is useful to use a life expectancy chart developed in 1980 in the United States. It covers the years 1900-2050. We have two curves on the graph. The first corresponds to the changes in life expectancy when we consider the entire existence of man - from the moment of birth. This curve indicates that year after year, people live 4 months longer. The second line corresponds to the changes in life expectancy for people over 65 and shows that the elderly population live only 18 days longer each year. Plotting these two curves on a graph, it was estimated that life expectancy would be about 82 years in 2009. This account turned out to be close to reality. As data from the United States show, life expectancy there was nearly 80 years in 2009. Since the method worked, the researchers used it again and, incorporating the latest data, estimated that the current average life expectancy is about 90 years.
The pandemic effect
Scientists' calculations and the upward trend in life expectancy were recently revised by the pandemic. According to the Central Statistical Office (GUS), life expectancy in Poland in 2020 compared to 2019 was reduced by 1.5 years for men and by 1.1 years for women. This may be due to two phenomena. The first are direct deaths caused by SARS CoV2 virus infections. The second are deaths indirectly related to the virus, that is, deaths resulting from the health care system being overwhelmed due to the pandemic and not being able to adequately care for patients with other conditions. Such a situation concerns not only Poland. There are reports from all over the world showing that the pandemic has caused an increase in the number of deaths caused by other diseases. A so-called health debt has been incurred. UK analyses show that over the next 5 years, UK residents will lose 60,000 years of life due to delays in cancer diagnosis.
The world's longest living person
Before the present calculations, we searched for hundreds of years for the answer to the question of how long humans can actually live. In our cultural circle we found the answer in the Bible. Methuselah from the Old Testament lived 969 years. However, biblical scholars claim that it was not years, but months. So Methuselah lived about 80 years. Maximum life expectancy is also mentioned in the Genesis. "And God said: My spirit shall not abide in man for ever, for he is flesh; his days shall be a hundred and twenty years." Bible prophecy seems to be coming true - so far, the longest living person in the world was Frenchwoman Jeanne Calment, who died at the age of 122 years and 164 days. Researchers in France have analyzed her family history from the early 18th century. They found that there were more long-lived people in her family (compared to the control group). Nevertheless, Jeanne Calment's son died at the age of 35, and her grandson (a doctor), at the age of 36. She loved chocolate, smoked several cigarettes a day for 96 years, and stayed slim all her life. She remained fit both physically and mentally until the age of 110.
You are as old as your vessels
There are people who are said to look young for their age or serious for their age. Jeanne Calment probably belonged to the former group, and her metric age did not coincide with her biological age. Can biological age be measured at all? It turns out that it can. William Osler, a Canadian physician who worked in the United States and England, was the author of the famous statement "You are as old as your vessels." The researcher noted that most people die from cardiovascular diseases caused by atherosclerosis. So the more progressive atherosclerosis, the more advanced the body's aging process. The primary indicator of the progression of vascular changes is their increasing stiffness, which results in high systolic pressure with normal diastolic pressure. There is a simple test - measuring pulse wave velocity which can measure the degree of vascular stiffness in a few minutes.
The faster the pulse wave travels, the stiffer the vessels. And the stiffer the vessels, the greater the risk of death.
Limit of cell division
Leonard Hayflick, an American biologist, first documented that the human body's capacity for renewal is limited. The scientist was involved in culturing fibroblasts, the primary cells of connective tissue. He placed them in a dish of culture fluid and observed their divisions. The cells divided until they began to touch each other. From the overgrown culture, Hayflick removed the fibroblasts and transferred them to the next dish. He waited until contact inhibition occurred and transferred them again. It turned out that even when he created ideal conditions for culture, the cells stopped dividing after 50 transfers. Conclusions? The number of divisions available to a single cell is limited. More precise analysis later revealed that chromosome doubling and shortening occur during the division. Specifically, telomeres, the structures that control the cell's division processes, shorten. Their length is therefore a good indicator of biological age. The shorter the telomeres, the more advanced the biological age.
Genes Reveal 'Biological Age'
We can also find out how old our body really is by studying genes. It is known that DNA is modified over time and under the influence of various factors. Changes occur through so-called epigenetic processes - small molecules are bound to alkalis, most commonly methyl groups, which can alter the function of a gene. So if we analyze all the genes and see how much they have been changed, we can estimate the biological age. It was handled by Steve Horvath, a researcher from the University of California. He developed an algorithm that converts genetic changes to biological age. Anyone can go to Horvath's website and, for $2,500, find out how old their body is. There is also a cheaper and simpler method. It was developed by researchers from MUW. Instead of analyzing the entire genome, they selected a few indicator genes and proved that biological age can also be estimated from this. This method is used, for example, in forensic science.
Lalonde report is still relevant
It is not difficult to see that life expectancy is extremely different in different geographical regions of the world. People live shorter lives in poor countries than in rich ones. In Western Europe, longer than in Central and Eastern Europe. Interestingly, the differences can be seen even when analyzing data from individual Warsaw districts. Why do people live longer in some regions and shorter in others? That was the question posed to experts by Marck Lalonde, Canada's Health Minister. He appointed a group of experts who analyzed a wealth of data and created a document called the Lalonde Report. It was released in the 1970s. It showed that lifestyle is the biggest determinant of longevity (40-60 percent). Social environment accounts for 20-25 percent, access to modern restorative medicine for 10-20 percent, and genetic factors for only 5-10 percent. A similar analysis was recently conducted by researchers from the United States. They found that lifestyle continues to be the biggest determinant of longevity.
What to do to live long
Since it's our behaviors and attitudes that matter most, it's worth spelling out what we should do and avoid in order to live a long and healthy life. This question was posed by the researchers associated with Boston University. In the 1950s, they began an epidemiological project that continues today called the Framingham Heart Study. Framingham, is a town near Boston with a demographic structure corresponding to the population of the United States. The project leaders were William Kannel and Thomas Dawber. It is to the Framingham Heart Study that we owe the commonly known knowledge that to live long and not get sick, you need to eat less, move more, and stop smoking. The scientists involved in the project have demonstrated how the different types of fat affect our bodies. They also helped us learn that there is good cholesterol and bad cholesterol, and what blood pressure values can pose health risks. The term "risk factor for premature death" was introduced. We still use it today. And every year the WHO publishes an updated list of risk factors that contribute to premature deaths. A recent summary shows that 8 of these are related to lifestyle. These are, in order of those associated with the highest number of deaths: hypertension, smoking, diabetes, physical inactivity, obesity, hypercholesterolemia, risky sexual behavior, and alcohol. Their prevalence is so high that we can soon expect a reduction in life expectancy. This is already evident in some countries, e.g. in the United States experts fear that today's teens may live shorter lives than their parents.
The successes of medicine
Every year, due to advances in medicine, we are better able to treat diseases. When I started as a doctor, type 2 diabetes was diagnosed much less frequently than it is today. However, the diagnosis meant the patient had only a 50 percent chance of surviving another five years. Today, nearly half of my patients have diabetes and live with the disease for many years. I even had a 90-year-old patient who had type 1 diabetes for over 50 years. Medicine can and does extend our lives. But in this case, we are adding years to living with a disease, and our goal is to add years to living a healthy life. Is it possible? There is plenty of research on this topic being done on all organisms from bacteria to primates. Scientists are looking for a method to extend life. For now, there is one known method that has worked for all species. It is caloric restriction. A well-known experiment on rodents is worth quoting here. The mice were divided into three groups. In the first, the rodents ate as much as they wanted, in the second, they were given a standard ration of food, and in the third, rations were cut by more than half of what the mouse wanted to eat. As a result, the life span of rodents in the third group increased from a few to several months. This is a very noticeable increase when you consider that these animals live 2-3 years in captivity. No such experiments were conducted on humans. However, there was an experimental group called the Calorie Restriction Society. The people belonging to it consumed up to 1,600 calories per day. The observations lasted 6 years. Whether these individuals lived longer - is not known. Nonetheless, there was a marked improvement in their risk profile, that is, they were less likely to develop coronary heart disease, stroke and other conditions.
Hope in a pill?
There have been recent claims that the drug that ensures longevity is metformin. It is a medication used in diabetes and extracted from French lilac. Not only does it lower sugar levels, but it accomplishes the primary goal of diabetes patient therapy, which is to protect against complications. The mechanism of action of metformin is quite complex and actually not fully understood. However, the drug is known to affect the energy metabolism of the cell, inducing a state of energy starvation in the cell. The results of animal studies suggest that metformin may extend life. For example, the following experiment was conducted on mice. Metformin was added to the water the rodents drank and it turned out that it clearly extended their lives. However, it cannot be said that everyone who takes metformin will ensure longevity. This drug also has contraindications and not everyone can take it. So it is better to focus on the fact that life expectancy depends primarily on how we live. Our fate is in our hands, and our old age can be both happy and healthy.