Ageing is not a disease, but is a multi-factorial process that leads to the progressive loss of functions. We are all too well aware of normal bodily changes as we age. We initially get a bit slower and then a little grey and bald, and then wrinkles come and memory goes. Cross-sectional studies of ageing tend to depict an essentially smooth and progressive decline of physiological function with increasing chronological age. However, although the young have high functional values and the very old low, between these limits values are widely scattered. There is no simple linear relation between age and functionality. When I meet some old friends whom I have not seen for some time I sometimes say, ‘Shall we start at the top or the bottom?’ We then tell about the pain in our foot, and work up the body to describe how our brain has declined.
One of the fairy tales collected by the Brothers Grimm in the early nineteeth century, ‘The Old Hound’, illustrates changes brought about by age:
A hound who had served his master well for years, and had run down many a quarry in his time, began to lose his strength and speed owing to age. One day, when out hunting, his master startled a powerful wild boar and set the hound at him. The latter seized the beast by the ear, but his teeth were gone and he could not retain his hold; so the boar escaped. His master began to scold him severely, but the hound interrupted him with these words, ‘My will is as strong as ever, master, but my body is old and feeble. You ought to honour me for what I have been instead of abusing me for what I am.’
Another of Grimms’ fairy tales, ‘The Duration of Life’, collected from a peasant in his field in 1840, presents a pessimistic outcome but adds a playful teleological explanation:
When God created the world he gave the ass, the dog, the monkey and man each a life-span of thirty years. The ass, knowing that his was to be a hard existence, asked for a shorter life. God had mercy and took away eighteen years. The dog and the monkey similarly thought their prescribed lives too long, and God reduced them respectively by twelve and ten years. Man, however, considered the thirty years assigned to him to be too brief, and he petitioned for a longer life. Accordingly, God gave him the years not wanted by the ass, the dog, and the monkey. Thus man lives seventy years. The first thirty are his human years, and they quickly disappear. Here he is healthy and happy; he works with pleasure, and enjoys his existence. The ass’s eighteen years follow. Here one burden after the other is laid on him; he carries the grain that feeds others, and his faithful service is rewarded with kicks and blows. Then come the dog’s twelve years, and he lies in the corner growling, no longer having teeth with which to bite. And when this time is past, the monkey’s ten years conclude. Now man is weak headed and foolish; he does silly things and becomes a laughing stock for children.
There are few if any organs in our body that do not decline in their function with age, and many deaths are due to age-related illnesses. But not everything is bad news. A major study by ELSA (English Longitudinal Study of Ageing) in the UK is designed to find out about the health of the elderly, and participants are interviewed every two years. It is encouraging and impressive that 60 per cent of those aged 80-plus describe their health as good to excellent. But that does mean that 40 per cent have health problems. The study also found that while arthritis is age-related, joint pain and back pain were not, and were no more common among the elderly than the young.
The study looked at the proportion of people who remain free of certain diseases, including four eye diseases, seven cardiovascular diseases and six other physical diseases. Around half of those aged 50–54 still had none of those diseases, but only around one in ten of those aged 75–79. Wealth and education lead to longer physical functioning, possibly because both lead to better personal care. Money matters: people in the richest part of London live 17 years longer than those in the poorest parts. Individuals who are 50–59 years old and from the poorest fifth of the population are over ten times more likely to die earlier than their peers from the richest fifth. The poor are more likely to be unhealthy, despite a fairly even distribution in the quality of healthcare between different wealth groups.
In a different study, it was found that participants with a high IQ as a child were more likely to have better lung function at the age of 79. This could be because people with higher intelligence might respond more favourably to health messages about staying fit.
Disability and frailty are common problems for the elderly. Those who are ill experience ageing very differently from those who are well. There are 75-year-old joggers and 75-year-olds who are very frail. Frailty is a condition associated with ageing whose symptoms include weight loss, decreased muscle mass and strength, weakness, lack of energy and reduced motor performance. The condition seems to spring from a general weakening of the body, including the skeletal, muscular, blood and hormonal systems. The most commonly used measures of disability are reports of problems with the basic activities of daily living such as mobility, looking after oneself by preparing meals, shopping, managing money and taking medication. While disability indicates loss of function, frailty indicates instability and the risk of loss of function. The frail person is at increased risk of disability and death from minor external stresses. Frailty may also be identified by particular clinical consequences such as frequent falls, incontinence or confusion. In many cases a single factor, such as undetected cardiovascular disease, can be the reason why people become frail. Instead of having classic symptoms such as a heart attack or a stroke, people may have partly blocked blood vessels in the brain or the legs, the kidneys or the heart, which can result in exhaustion or mental confusion or weakness or a slow walking pace. It has been found that those people who had a positive outlook on life were significantly less likely to become frail.
As we age, our cells become less efficient and our bodies become less able to carry out their normal functions. Muscles lose strength, hearing and vision become less acute, reflex times slow down, lung capacity decreases, and the heart’s ability to pump blood may be affected. In addition, the immune system weakens, making it less able to fight infection and disease. Heart pumping giving maximum oxygen consumption declines about 10 per cent every ten years in men, and in females a bit less; maximum breathing capacity declines about 40 per cent between ages 20 and 70; the brain shrinks and loses some cells; kidneys become less efficient and the bladder gets smaller; muscle mass decreases by about 20 per cent between 30 and 70 years, though exercise reduces this; and bone mineral is lost from age 35; sight may decline from 40 and hearing declines when older. These changes in our bodies with age are not due to ill health but are, alas, normal, and they can cause health problems.
Once adults reach 40, they start to lose just over 1 per cent of their muscle each year. This could be due to the body’s failure to deliver nutrients and hormones to muscle because of poorer blood supply. Tendons, which connect muscles to bone, and ligaments, which hold joints together, become less elastic and are easier to tear. We also get slower in physical activities, as I know all too well. The good news is that one in five people aged between 65 and 74 are doing recommended levels of exercise. But physical labour can also have negative effects—lawyers and priests over 55 die at lower rates than blacksmiths and ironworkers, and at even lower rates when over 75. Mammalian muscles can regenerate, but in mice the old muscle regenerates poorly. Joining the muscles of old and young mice together resulted in the old muscle regenerating better, and the young a bit worse.
Men and women between 60 and 96 years of age who suffered from loss of body mass and strength, and who did a moderate amount of strength training twice a week, had a significant increase in muscle after eight to twelve weeks. Long-term physical activity postpones disability and sustains independence, even for the chronically ill. Regular physical activity can also help to prevent some important conditions in the elderly that may lead to disability including osteoporosis, type 2 diabetes, cardiovascular disease, anxiety and depression. It can also reduce the risk of falls and therefore subsequent fractures. A
goal to work towards is 30 minutes of at least moderately intense physical activity on at least five days of the week. Joan Bakewell, 77, of whom more later, told me, ‘I am not as able as I was and do have some aches and pains, but I have a fetish for staying fit and have done pilates exercises twice a week for fifteen years. I did not want my posture to go, as I noticed I was beginning to stoop.’
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Most human deaths are attributable to an age-related disease and so, not surprisingly, becoming a centenarian is associated with having avoided common diseases until advanced in age. A period of not having good health for the elderly will usually involve some seven years for men, and ten for women. Coronary heart disease, stroke, cancer, osteoporosis, diabetes and dementia are just some of the conditions that more and more people will be battling with in later years. The figures will continue to go up as people live longer than ever before. Obesity increases the likelihood of death from all causes, particularly coronary artery disease and stroke. In addition to these diseases, obese patients suffer an increased incidence of arthritis. The conditions associated with obesity are also associated with ageing. The proportion of intra-abdominal fat, which is related to increased morbidity and mortality, progressively increases with age. Targeting weight loss in the elderly can therefore reduce morbidity from cardiovascular risk factors, and also arthritis.
The leading causes of death in the United States have changed dramatically. In 1900 the top three causes of death were all related to infectious diseases, but by 2009 the leading causes of death for all ages were diseases of the heart and cancer, which together account for 50 per cent. The top four causes of death for persons aged 65 and older—diseases of the heart, cancer, brain dysfunctions related to disease of the blood vessels supplying the brain, and respiratory diseases—were the same as for all ages. In the UK the main causes of death are heart disease and stroke. There is an elusive distinction between the effects of ageing, and having a disease when old, but it is generally accepted that fundamental to ageing is an increasing vulnerability to diseases such as heart disease.
Coronary heart disease is the leading killer of older people and half of all heart attack victims are over 65. Participating in light to moderate physical activities significantly decreases mortality rates in elderly patients. Heart disease is the result of the heart’s blood supply being blocked or interrupted by a build-up of fatty substances in the coronary arteries. Over time, the walls of arteries can become furred up with fatty deposits, a process known as atherosclerosis. When the coronary arteries become narrow due to a build-up of these fatty deposits, the blood supply to the heart will be restricted. A heart attack occurs when blood flow to an area of heart muscle is completely blocked. This prevents oxygen-rich blood from reaching heart muscle and so causes it to die, and then circulation of the blood fails. Without quick treatment, a heart attack leads to serious problems and often death. While men have markedly higher rates of coronary heart disease in middle age than do women, women’s rates of coronary disease begin to rise sharply after menopause.
Failure of the blood supply can also cause strokes. A stroke occurs when the blood supply to the brain is disrupted in some way and the brain cells are deprived of oxygen and other nutrients, causing some cells to become damaged and others to die. The effects of a stroke depend on where the brain was injured, as well as how much damage occurred. The after-effects of stroke are very varied and depend on how and where nerve cells die. Most of the damage caused to the brain is the result of dying nerve cells releasing toxins that damage even more of the brain. A stroke can impact on any number of areas including the ability to move, see, remember, speak, reason, and read and write. Every year about 150,000 people in the UK have a stroke—that’s one person every three and half minutes, every day. A study of elderly stroke victims in a working-class region of London found that many regarded it as a normal crisis in their lives. Although strokes can happen at any age, the vast majority occur in people over 65 years old. However, a new study shows more and more Americans suffering from stroke earlier in life than ever before, indicating that stroke is no longer just an affliction of old age.
Cancer is fundamentally a disease of the elderly, the incidence of cancer in those over 65 being ten times greater than in those younger. Nearly three quarters of cases are diagnosed in people aged 60 and over, and more than a third of cases in people aged 75 and over. More than three quarters of cancer deaths occur in people aged 65 years and over. Although there is a higher number of cancer deaths in the over 65s, cancer causes a greater proportion of deaths in younger people. Among elderly men, cancers of the prostrate and colon are the most common, while for women it is breast cancer. About 80 per cent of all breast cancers occur in women aged over 50.
The relationship between cancer and ageing is quite complex. Genomic instability, DNA damage, is a hallmark of most cancers, and is also a hallmark of ageing, as we will see. There have to be a number of changes to the genes within a cell before it turns into a cancer cell. It then takes time for further changes to occur for the cells to become malignant. The relationship to ageing is probably related to the increased time cells have to develop abnormalities that increase the risk of cancer, and also the increase in time that they are exposed to a cancer-inducing environment. A surprising statistic is that the potential gain in life expectancy which could result from the complete elimination of mortality from cancer in the US would not exceed three years if one were to consider cancer independently of other causes of death.
Cells can respond to new situations by increasing their growth in ways that do not necessarily lead to cancer, but have other effects. The prostate in older men is all too good an example. This is due to increased proliferation of the epithelial cells and fibroblasts, and an increase in size of the smooth muscle. This results in increased urination as the prostate protrudes into the bladder. Why this should occur with age is just not known, and it all too often can develop into a tumour. But not all abnormal increases in growth are cancerous, thankfully.
Decline of the immune system with age is serious. In the elderly, many alterations of both innate and acquired immunity have been described. This process is responsible for increased susceptibility to infectious diseases such as flu and pneumonia, as well as being at the root of the biological mechanisms responsible for inflammatory age-related diseases. In the USA 90 per cent of deaths from flu and pneumonia are in people aged over 65 years.
Osteoarthritis is a type of arthritis and some 8 million people in the UK suffer from it. It affects mainly older people starting at around age 45, and is caused by the breakdown and eventual loss of the cartilage that serves as a cushion between the bones of the joints. Loss of the cartilage cushion causes friction between the bones, leading to pain and limitation of joint mobility. People with osteoarthritis usually have joint pain and limited movement. Unlike some other forms of arthritis (there are over a hundred types), osteoarthritis affects only joints and not internal organs. More than half of the population aged 65 or older would show X-ray evidence of osteoarthritis in at least one joint. Both men and women have the disease. It is due to a combination of factors, including being overweight, the ageing process, joint injury, and stresses on the joints from certain jobs and sports activities.
Osteoporosis is a silent disease in which bones become extremely fragile. The bone mineral density is reduced, and bone structure is disrupted. If left untreated, it can progress painlessly until a bone breaks, typically in the hip, spine or wrist, and these breaks are extremely painful and can take a long time to heal. It is claimed that one in every two women and one in every four men over 50 will break a bone due to osteoporosis. Gout, however is not age-related.
Falls are amongst the most common and serious problems facing the elderly. They can lead to death, reduced function and admission to a nursing home. About half of the over-65s have a fall each year and the numbers increase with age. Cognitive impairment and dementia increase the risk of falls and the risk of fr
actures to bones is greater. Balance problems and dizziness are considerably more common the older the person—three out of five women aged 80 and over experienced one or both of these at least sometimes, compared with only one out of five women in their 50s. Repeated falls can lead to the need for long-term care. Difficulties with walking and climbing stairs are all too common amongst those over 75. More than 2,300 older people fall every day and 80,000 of those who have fallen during the year are afraid to leave their homes. Exercise programmes can help in preventing falls.
Older people have an abnormal gait when walking, and this is evident in about one third of those over 65. The characteristics include slow speed, short step length and large variability, narrow stride width, and stepping frequency. Uneven pavements—in London one in five pavements is in a poor state of repair—can be hazardous. Elderly people could one day be relying on a bodysuit, rather than a Zimmer frame, for support. Scientists in Japan are developing the ‘Michelin gran’ Lycra suit which is covered in pairs of inflatable ‘muscles’ which assist the wearer’s real muscles. When they inflate, they help the wearer move their limbs with more strength and stability.
Type 2 diabetes is most often seen in older adults, with half of all cases diagnosed in people of 55 and over. It is by far the most common form of diabetes, and occurs when the body produces insulin but the cells no longer respond by allowing entry of glucose, especially in muscle, fat and liver cells. About 90 per cent of patients who develop type 2 diabetes are obese. Both being overweight and lack of mobility promote the disease.
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