Chapter 27
In Search of the Elixir of Youth to Cold Water and Hormesis
Females also tend to convert more food into white adipose tissue compared to males, who convert their food into muscle (a good thing) and circulating lipids including LDL-cholesterol (bad cholesterol). Cholesterol is one of the leading risk factors for cardiovascular disease. The female hormone oestrogen has protective cardiovascular benefits, reducing the levels of LDL-cholesterol and increasing HDL-cholesterol (good cholesterol), thus protecting pre-menopausal women from heart disease. Oestrogens further protect the inner lining of blood vessels from injury, dilate blood vessels and thus lower blood pressure and protect against atherosclerosis by reducing both clots and hardened arteries. All of these factors constitute women’s superior cardiovascular profile and longer lives. Finally, in some countries men are also more frequently exposed to occupational hazards – they drive more miles, drink more alcohol, smoke more and are more often exposed to trauma, including homicide. Although we ladies in the Western world live longer, as societies evolve, this gender gap is narrowing and men who adopt better health behaviours can further reduce the difference – where there is the will to do so. A well-known scientist in this field, Caleb Finch, when asked how long could we live if we didn’t age or did so at the turtle’s rate, reflected that, ‘In theory, if mortality rates did not increase as usual during ageing, humans would live hundreds of years. I have calculated for humans that at mortality rates of 0.05 per cent per year, as found at age 15 in developed countries, the median lifespan would be about 1,200 years.’ Of course, what happens is that mortality rates accelerate as we get older – they do not stay constant at the rate they were when we were aged 15 in contrast to negligible senescent animals. As Finch explains, negligibly senescent animals enjoy a 1–2 per cent death rate once they get past their seventieth year in contrast to human mortality rates, which accelerate past 70 years. At 65–70 we have a 1:100 chance of dying in the next five years, this rises to a 1:10 chance after age 85. Compare this with 1:10,000 for six-year-olds. At present, the reasons why some animals have negligible senescence are not clear. It may be an evolutionary development which gives them a reproductive advantage, or simply an accident. There is much research activity in this space which could hold the answer to the ‘elixir of youth’ or the ‘elixir of life’ for humans. A more realistically achievable goal than negligible senescence in our lifetime is a modest deceleration in the rate of ageing sufficient to delay all ageing-related diseases by about seven years. This target is chosen because the risk of death and most other negative attributes of ageing tends to rise exponentially throughout the adult lifespan with a doubling time of approximately seven years.
Chapter 7: In Search of the Elixir of Youth
Such a seven-year delay would yield health and longevity benefits greater than what could be achieved with the elimination of cancer or heart disease. If we succeeded in slowing ageing by seven years, which scientists consider a realistic target, people who reach the age of 50 would have the health profile and disease risk of a 43-year-old; those aged 60 would resemble 53-year-olds, and so on. Equally important, once achieved, this seven-year delay would yield equal health and longevity benefits for all subsequent generations, much the same way that children born in most nations today benefit from the discovery and development of immunisations. I believe that this is an achievable goal and many of the elements covered in this book – friendship, stress relief, laughter, purpose, sleep, foods, physical activity and positive attitude do exactly that – delay age-related diseases and disorders and death by up to seven years or more.The earlier we address risk factors which influence the ageing process, the more reserve we can build up in body and brain capacity and the more likely it is that we will achieve a seven-year delay in ageing.
Knowing why some animals have particularly long lifespans should inform how we might be able to manipulate cell functions or structures to enhance longevity and reduce age-related diseases.
Chapter 8: Cold Water and Hormesis
THE NEXT TIME YOU GO TO A FANCY SPA AND ROTATE BETWEEN exercise, sauna, steam room and cold-water pools, take a moment to pause and reflect on how ancient these rituals are. People have derived pleasure from bathing and water for around 4,000 years. Public baths existed in early Egyptian palaces as early as 2,000bc and bathing also occupied an important place in the life of the ancient Greeks. However, we know much more about the high degree of sophistication of Roman baths, thermae – a complex of rooms designed for public bathing, relaxation and social activity – just like our modern day spa.
The Roman technique of bathing followed a somewhat standardised pattern. The bather first entered the apodyterium, where he undressed. He was then anointed with oil in the unctuarium before entering a room or court, where he indulged in rigorous exercise. After this activity, he proceeded to the hot room and then the steam room where his skin was ridded of its accumulation of oil and perspiration. The bather then moved to the tepidarium (warm room) and afterwards to the frigidarium (cold room), where there was frequently a cold water swimming pool. The bathing process was completed after the body was once more anointed with oil. What a pleasant way to pass a few hours.
The use of water for therapeutic purposes is an ancient practice. These days, water therapy is used to treat musculoskeletal disorders such as arthritis or spinal cord injuries and prescribed for patients suffering from burns, stroke or paralysis. As with the Roman bath, integral to the bathing experience is cold water exposure. There is copious evidence for the health benefits of cold water on a number of systems and pathways involved in the process of ageing.
Chapter 8: Cold Water and Hormesis
Cold water immersion provides a stimulus to our physiological systems which is related to the phenomenon of hormesis, whereby small amounts of a harmful or painful agent are actually good for us. The work on this counterintuitive phenomenon – in which moderate doses of stressors such as cold exposure, radiation, noxious compounds and starvation prove beneficial rather than harmful – intrigues gerontologists. Laboratory organisms often survive longer after exposure to such stressors and we are of course eager to learn whether and how we can harness this response to enhance cell life. What we do know to date is that exposure of cells to mild stress stimulates the synthesis of proteins, which improve the function and survival of cells without interference in their ability to reproduce and divide. We believe that the reason is that the triggering of one recovery mechanism in the cell improves the functioning of other repair and recovery systems. Whatever the reason, hormesis is fascinating. We can use this to explain why cold water exposure is so good for us and good for ageing.
A cold shower or cold water immersion is a physiological stress which has a hormetic effect as it forces the body to recover to normal core temperature after the cooling stimulus, resulting in indirect benefit to many systems and organs. Other moderate stressing agents could therefore theoretically be beneficial too – for example, hypoxic stress (holding one’s breath), oxidative stress (hyperventilation) and heat shock (sauna), but these have not been tested to the same degree as cold water, in the context of ageing.
Chapter 8: Cold Water and Hormesis
Cold water immersion or cold water showers are so effective in delivering a large-scale stimulus to the body because the number of cold receptors in the skin is up to ten times more than warm receptors. Furthermore, the ability of water to conduct temperature is 30 times stronger than air. On exposure of the skin to cold water, blood vessels contract and raise blood pressure, which, coupled with the temperature shock, causes electrical impulses from peripheral nerve endings to travel to sensory centres in the brain. The result is an increase in important chemicals and nerve signals. One of these chemicals is noradrenaline, a critical neurotransmitter that is part of our ‘flight-or-fight’ response, which rises four-fold on cold water exposure. Noradrenaline boosts performance of cells in both the brain and body and regulates a host of functions such as heart rate, blood pressure, blood flow to muscles, power of contraction of skeletal muscles and release of energy. Cold exposure also releases noradrenaline in the major brain areas that control emotions, concentration and memory, thereby affecting how alert we are, how good our memory is, our levels of interest in things, our mood and how the body responds to pain. Almost all of our organs use noradrenaline and the functions that it contributes to are central to the ageing process. Because responsiveness to noradrenaline declines with age, any stimulus which enhances its activity is important to ‘ageing’ physiology. One of my neuropsychology colleagues at Trinity College, Dublin has hypothesised that stimuli that excite the release of brain noradrenaline, such as cold water, may prevent dementia.