How old are you, really?

When the legendary jazz saxophonist Charlie Parker died, the coroner estimated the gifted heroin addict, who died of a bleeding ulcer and pneumonia, was aged between 50 and 60. Parker was 34.

The parity between chronological age and physical age is immensely variable as numerous factors are involved. An almost equal number of theories exist as to the cause of physical ageing.

Some are based on the behaviour of the body’s cells. Program theory is based on the number of times cells in lab conditions will replicate before they die, whereas cellular theory is based on cell debilitation over time, supporting the idea that increasing the metabolism speeds ageing due to oxidative stress.

As cells age they undergo nervous system degeneration with concurrent effects on all physiological processes, leading to decline in cell function that we call ageing. This is called neuro-ageing.

Mutating autoimmune theory is also related to degeneration of cell function over time. As cells age, they mutate and secrete proteins that solicit the immune response, shutting down the cell. This suggests cell mutation over time causes biological errors that contribute to the demise of the organism.

In lab tests when lipids in human cell membranes are exposed to radiation or free radicals, the membrane ruptures and the cell dies. Some scientists relate free radical theory to ageing.

Error theory attributes physical ageing to the alteration of DNA as a result of exposure to ultraviolet, x-rays, chemicals and other external factors, causing abnormal malfunction leading to problems such as cancer. Other theories look at diet and body composition as critical factors.

The nutritional model theory rests on the assumption that lean mass, as opposed to adipose tissue, will result in a healthier person. Research shows if an animal is fed around half of the energy intake it normally consumes it will live longer and be healthier. Finally, the collagen theory of ageing postulates that the decrease in collagen contributes to hypertension and other organ malfunctions.

None of these theories is totally accepted as the reason for ageing. Some scientists have hypothesised that it might be a combination of several or all of these factors.

How physical age is assessed

Type ‘physical age’ into an internet search engine and you will be able to take an online test to determine how old you ‘really’ are. That is, how old your body is, rather than how many birthdays you have counted.

These tests are usually based on answers to questions about lifestyle habits and family medical history. A more immediate marker is how quickly and completely a person can recover from injury or illness.

In 1959 Dr James Hollingsworth, studying survivors of the Hiroshima bomb, introduced the use of biomarkers to measure human ageing. Biomarkers measure physical functions, some related to vital organs, others to the central nervous system.

Beginning at about age 35, most people suffer a decline in functions essential for daily activities. Developed by United States doctor Richard Hochschild, the H-Scan test evaluates key functions, using a computer. The 12 biomarkers include memory, reactions, hearing, vision, agility, decision speed, movement speed, tactile sense and lung function.

By measuring such biomarkers of ageing and comparing scores to norms by age and sex, the test determines a person’s functional age as opposed to their chronological or calendar age.

Functional declines proceed at different rates in different individuals. Genetic factors play a role, but so do environment, diet and lifestyle, providing evidence that intervention in the ageing process is possible.

Cellular biomarkers

Scientists searching for conclusive biomarkers are looking at DNA repair function for answers. Studies have shown chromosomes become shorter each time the cell divides, as their ends are removed or fail to be replaced. These ends, called telomeres, may hold the key to measuring ageing in terms of functionality in cells and tissue where the ability to replicate is critical, in wound healing response, for example.

Telomere shortening is a biomarker of cellular senescence and is associated with a wide range of age-related diseases as well as factors such as lung functionality in smokers.

Oxidative stress is also associated with physiological ageing and several age-related diseases. Non-human studies have suggested that variants in oxidative stress genes may contribute to both telomere shortening and biological ageing.

Research has shown that oxidative stress genes may also be involved in pathways that lead to both telomere shortening and physiological ageing in humans. Blood and saliva can also reveal information about bone density and hormonal levels. People can even send DNA samples for mail-order analysis to find out what their congenital predispositions might be, but medical doctors advise against this type of diagnosis.

Changes in body function are difficult to pinpoint accurately, even using biomarkers. Functionality, in terms of a person’s ability to care for themselves and interact meaningfully, also depends on mental age which is very much dependent on character and outlook.

Intervention

While no one can take years off their chronological age apart from by fibbing, anyone can improve their physical age and they can do it at any stage of their life.

Positive habits such as regular exercise and moderation of intake of toxins as well as a balanced, healthy diet with vitamins and supplements all have a positive effect on physical ageing.

Commonsense measures such as avoiding exposure to damaging environmental influences or using adequate protection also play a part in living not so much longer – although this is a benefit – but better.