Health Matters: The search for longevity continues

Conway McLean, DPM, Journal columnist

Humanity has longed for immortality, or at least real longevity, for all of recorded history. Is the extension of human life more than a dream? Americans born today can expect to live to an average age of about 79. Not that long ago, life expectancy was closer to 54, but a significant increase in life span has occurred over the last century. Will this trend continue?

Some suggest all the possible mechanisms that can increase longevity have already been exploited. Many scientists believe natural selection has played a part in extending human life span and further attempts to tinker with longevity, either through genetic manipulation or pharmacologically, will be fruitless. But the search for extending the human life span, begun generations ago, continues.

As most of us are aware, larger mammals tend to have a longer life expectancy, although many exceptions exist. Compare an elephant, with a life span of roughly 60 years, with that of a mouse who lives about a year. Yet these are gross generalizations. Our understanding of the factors contributing to the life span of various species remains incomplete. Regardless, humans are fortunate amongst the animal kingdom since we have an unusually long life span compared to similar sized mammals.

The average life expectancy for a human has increased tremendously over the last hundred years but was relatively stable for centuries. Stone Age peoples lived into their mid-20’s or 30’s, with the average total span of life relatively stable well into the 18th century. It wasn’t until the 19th century that the average person might be expected to live longer. The United Nations began tracking human longevity around the 1960’s when the average person would be expected to live only into their 50’s (although infant mortality was much worse in earlier times, skewing the results downward). The life span today is about 72 years, a tremendous increase.

Explanations for this increase are many, but all are theories. This increased longevity is likely attributable in part to environmental changes. Our water sources are better controlled and cleaner. We know much more about diet and, overall, many of the world’s population have been eating a more balanced, complete diet (until the advent of processed, fast foods). Our understanding of hygiene has reduced the impact of infectious disease. Obviously, medical care has improved at all ages, as has access to providers.

Specific answers to improving human life span are extraordinarily difficult to find. Our longer lives are part of the reason, making studies difficult, conclusions imprecise. More importantly, restricting and controlling someone’s diet, consistently and thoroughly, for the length of time required to gather information about someone’s life expectancy, is impossible. And human studies are tremendously expensive. Plus, people are loathe to eat what you tell them to for a day, much less for years. To draw definitive conclusions, a large number of participants are required to attain statistical validity. And genetic factors are obviously impossible to control. Consequently, most studies involving aging, life span, and anti-aging interventions are based on models and projections.

Many aspects of our normal routine impact how long we live. One component recognized as critical is diet. A healthy eating pattern is vitally important, the benefits of consuming a variety of food types, a diet based on vegetables, fruit, nuts, whole grains, polyunsaturated fatty acids, and omega-3 fatty acids. Numerous studies demonstrate the benefits of limiting red and processed meats, as well as beverages with added sugar. Food sources high in trans fats and sodium should be strongly avoided. And of course, cigarette smoking is not conducive to a long life span.

Another vital component of a healthy lifestyle is physical activity. A frequently quoted number calls for 3 and a ½ hours of moderate to vigorous physical activity each week. The form of exercise may vary greatly with differing benefits but, regardless, the human body needs to move. Many authorities would say this, in terms of priority, is the most important thing associated with living longer and healthier. Exercise is especially important for lengthening active life expectancy. This describes a life lived without disease and without physical and mental disability, even into the later years.

Weight matters. Although exceptions exist, maintaining a normal body weight is essential to longevity, considered (very) approximately a body mass index between 18.5 and 24.9. The associations between obesity and disease are well-known (although BMI is recognized as inaccurate and misleading). From heart disease to diabetes, excess body weight (especially around the middle), is associated with a higher risk of many chronic, life-shortening diseases.

Healthy daily practices can help you stay active and fit into your 70’s and 80’s. Seniors, at least in developed countries, are healthier nowadays. Without question, advances in medicine are a significant factor in this. A long-term study of a particular religious group, who practiced a healthy lifestyle, revealed they did indeed stay healthier in their later years. Their life expectancy on average was nearly a decade longer than most Americans. Their age-enhancing practices included regular exercise, a vegetarian diet, avoiding tobacco and alcohol, and maintaining a healthy weight.

In future, longevity may be enhanced with an anti-aging drug called rapamycin. Originally developed as an immunosuppressant for organ transplant patients, it has gained notoriety because of its ability to extend life significantly…..in mice. But rapamycin has not been approved for use in humans, yet. The market, and therefore the research, is huge. Still, many gerontologists see this and similar drugs as our best hope for pharmacologically slowing down the aging process.

It is possible that humans have already achieved their maximum life span. A furthering of life may be impossible to achieve. The documented record for life span over the last 100 years indicates the limit of human life is around 122 years. Since no one has lived beyond this, it is possible this is the end point.

History is littered with tales of the search for eternal youth. But instead of directing our attention at treating disease, perhaps life expectancy can be increased by focusing on aging itself. Scientists have found ways to prolong the lives of various less-complex species, creatures like worms, mice, even monkeys.

Clearly, we need to know more about the biology of aging. Until such information is obtained, the best way to boost your chances of living a long, active life is to follow some well-established recommendations: eat well, exercise regularly, get plenty of sleep, and stay away from bad habits. (Ancient wisdom, likely provided by your parents!) Beyond that, we don’t know enough to say.

EDITORS NOTE Dr. Conway McLean is :a podiatric physician now practicing foot and ankle medicine in the Upper Peninsula, having assumed the practice of Dr. Ken Tabor. McLean has lectured internationally on surgery and wound care, and is board certified in both, with a sub-specialty in foot orthotic therapy. Dr. McLean welcomes questions, comments and suggestions at drcmclean@penmed.com.


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