Oxford Medical Publications Oxford Handbook of Geriatric Medicine

There are many differences between old and young people. In only some cases are these changes due to true ageing, i.e. due to changes in the characteristic(s) compared with when the person was young.

Changes not due to ageing

• Selective survival. Genetic, psychological, lifestyle, and environmental factors influence survival, and certain characteristics will therefore be over-represented in older people

• Differential challenge. Systems and services (health, finance, transport, retail) are often designed and managed in ways that make them more accessible to young people. The greater challenge presented to older people has manifold effects (e.g. impaired access to health services)

• Cohort effects. Societies change, and during the twentieth century, change has been rapid in most cases. Young and old have been exposed to very different physical, social, and cultural environments

Changes due to ageing

• 1° ageing. Usually due to interactions between genetic (intrinsic, ‘nature’) and environmental (extrinsic, ‘nurture’) factors. Examples include lung cancer in susceptible individuals who smoke, hypertension in susceptible individuals with high salt intake, and diabetes in those with a ‘thrifty genotype’ who adopt a more profligate lifestyle. Additionally there are genes which influence more general cellular ageing processes. Only now are specific genetic disease susceptibilities being identified, offering the potential to intervene early and to modify risk

• 2° ageing. Adaptation to changes of 1° ageing. These are commonly behavioural, e.g. reduction or cessation of driving as reaction times ↑

Ageing and senescence

Differences between old and young people are thus heterogeneous, and individual effects may be viewed as:

• Beneficial (e.g. ↑ experiential learning, ↑ peak bone mineral density (reflecting the active youth of older people))

• Neutral (e.g. greying of hair, pastime preferences)

• Disadvantageous (e.g. ↓ reaction time, development of hypertension)

However, the bulk of changes, especially in late middle and older age, are detrimental, especially in meeting pathological and environmental challenges. This loss of adaptability results from homeostatic mechanisms that are less prompt, less precise, and less potent than they once were. The result is death rates that, from a nadir of around 8 years old, ↑ exponentially with age. In very old age (80–100 years), some tailing off of the rate of ↑ is seen, perhaps due to selective survival, but the ↑ continues nonetheless.

Theories of ageing

With few exceptions, all animals age, manifesting as ↑ mortality and a finite lifespan. Theories of ageing abound, and over 300 diverse theories exist. Few stand up to careful scrutiny, and none has been confirmed as definitely playing a major role. Four examples follow.

Oxidative damage

Reactive oxygen species fail to be mopped up by antioxidative defences and damage key molecules, including deoxyribonucleic acid (DNA). Damage builds up until key metabolic processes are impaired and cells die.

Despite evidence from in vitro and epidemiological studies supporting beneficial effects of antioxidants (e.g. vitamins C and E), clinical trial results have been disappointing.

Abnormal control of cell mitosis

For most cell lines, the number of times that cell division can occur is limited (the ‘Hayflick limit’). Senescent cells may predominate in tissues without significant replicative potential such as cornea and skin. The number of past divisions may be ‘memorized’ by a functional ‘clock’—DNA repeat sequences (telomeres) shorten until further division ceases.

In other cells, division may continue uncontrolled, resulting in hyperplasia and pathologies as diverse as atherosclerosis and prostatic hyperplasia.

Protein modification

Changes include oxidation, phosphorylation, and glycation (non-enzymatic addition of sugars). Complex glycosylated molecules are the final result of multiple sugar–protein interactions, resulting in a structurally and functionally abnormal protein molecule.

Wear and tear

There is no doubt that physical damage plays a part in ageing of some structures, especially skin, bone, and teeth, but this is far from a universal explanation of ageing.

Ageing and evolution

In many cases, theories are consistent with the view that ageing is a by-product of genetic selection—favoured genes are those that enhance reproductive fitness in earlier life but which may have later detrimental effects. For example, a gene that enhances oxidative phosphorylation may ↑ a mammal’s speed or stamina, while ↑ the cumulative burden of oxidative damage that usually manifests much later.

Many genes appear to influence ageing; in concert with differential environmental exposures, these result in extreme phenotypic heterogeneity, i.e. people age at different rates and in different ways.

Demographics: life expectancy

• Life expectancy (average age at death) in the developed world has been rising since accurate records began and continues to rise linearly

• Lifespan (maximum possible attainable age) is thought to be around 120 years. It is determined by human biology and has not changed

• Population ageing is not just a minor statistical observation, but a dramatic change that is easily observed in only a few generations

• In 2002, life expectancy at birth for women born in the United Kingdom (UK) was 81 years, and 76 years for men

• This contrasts with 49 and 45 years, respectively, at the end of the nineteenth century

• Although worldwide rises in life expectancy at birth are mainly explained by reductions in perinatal mortality, there is also a clear prolongation of later life

• Between 1980 and 2013, UK life expectancy at age 65 ↑ by 5.3 years for men and 3.9 years for women (see Table 1.1)

• While projections suggest this trend will continue, it is possible that the modern epidemic of obesity might slow or reverse this

Table 1.1 Predicted UK life expectancy at age 65

Period	Women (years to live)	Men (years to live)
1980–82	16.9	13
1996–98	18.4	15
2011–13	20.8	18.3

Adapted from data from the Office for National Statistics licensed under the Open Government Licence v.3.0.

Individualized life expectancy estimates

UK population statistics (Office for National Statistics) reveal that mean ♂ life expectancy is 78.7 years. However, this is not helpful when counselling an 80-year-old. Table 1.2 demonstrates that as a person gets older, their individual life expectancy actually ↑. This has relevance in deciding on healthcare interventions.

Table 1.2 Predicted life expectancy at various ages for men (UK)

Age at time of estimate	Years left to live	That is, death at age
Birth	78.7	78.7
65	18.2	83.2
85	5.8	90.8
95	2.8	97.8

Adapted from data from the Office for National Statistics licensed under the Open Government Licence v.3.0.

More accurate individualized estimates should take into account sex, previous and current health, longevity of direct relatives, as well as social and ethnic group.

Life expectancy at age 65 is also improving with time, as shown in Table 1.1.

Demographics: population age structure

Fertility

Fertility is defined as the number of live births per adult ♀. It is currently around 1.9 in the UK. If this rate were maintained, then in the long term, the population would fall unless ‘topped up’ by net immigration. In contrast, during the ‘baby boom’ years of the 1950s, fertility rates reached almost 3. This bulge in the population pyramid will reach old age in 2010–2030, ↑ the burden on health and social services.

Deaths and cause of death

The driver of mortality decline has changed over the twentieth century, from reductions in infant/child mortality to reductions in old age mortality.

• Infant mortality accounted for 25% of deaths in 1901 but had fallen to 4% of deaths by 1950. Currently, over 96% of deaths occur at >45 years

• Deaths at age 75 and over comprised 12% of all deaths in 1901, 39% in 1951, and 65% in 2001

The most common cause of death in people aged 50–64 is cancer; 39% of ♂ and 53% of ♀ deaths are due to cancer. Over the age of 65, circulatory diseases (heart attacks and stroke) are the most common cause of death. Pneumonia as a cause of death also ↑ with age to account for 1 in 10 among those aged 85 and over.

All these statistics rely on the accuracy of death certification (see Documentation after death, pp. 648–649) which is likely to reduce with ↑ age.

Population ‘pyramids’

These demonstrate the age/sex structure of different populations. The shape is determined by fertility and death rates. ‘Pyramids’ from developing nations (and the UK in the past) have a wide base (high fertility, but also high death rates, especially in childhood) and triangular tops (very small numbers of older people). In the developed world, the shape has become more squared off, with some countries having an inverted pyramidal shape—people in their middle years outnumber younger people—as fertility declines below replacement values for prolonged periods.

An interactive UK population pyramid can be seen on the Office for National Statistics website ( http://www.ons.gov.uk/ons/interactive/uk-population-pyramid---dvc1/index.html).

Demographics: ageing and illness

Healthy life expectancy and prevalence of morbidity

Healthy life expectancy is that expected to be spent in good or fairly good health. As total life expectancy rises, it is better for society and the individual to spend as much of this extended life in good health as possible.

It is not known whether ‘compression of morbidity’—where illness and disability are squeezed into shorter periods at the end of life—can be achieved. Trends in data from the United States (USA) suggest that compression of morbidity is occurring, but challenges to public health are different in the UK. Obesity and lack of exercise may negate diminishing morbidity from infectious diseases; as more people survive vascular deaths, they might develop dementia (and other old age-associated diseases). The UK Office for National Statistics compared estimates of healthy life expectancy from 2000 to those from a decade later and showed that we are living longer and that more of this time will be in relative health. A 65-year-old in 2011 should expect to live over half their upcoming life free from disability. However, there are significant variations, depending on the region, socio-economic status, and sex.

Social impact of ageing population

Those >80 are the fastest growing age group in the UK. Currently, around a quarter of the population is >60 years old, but by 2030, this will rise to a third. Governments can encourage migration (economic migrants are mostly young) and extend working lives (e.g. ↑ pensionable age for women), but these will have little effect on the overall shift. The impact of this demographic shift on society’s attitudes and economies is huge. Examples include:

• Financing pensions and health services—in most countries, these are financed on a ‘pay-as-you-go’ system, so they will have to be paid for by a smaller workforce. This will inevitably mean greater levels of taxation for those in work or a reduction in the state pension. Unless private pension investment (which works on an ‘insurance’ system of personal savings) improves, there is a risk that many pensioners will continue to live in relative poverty

• Healthcare and disability services—the prevalence and degree of disability ↑ with age. American Medicare calculations show that more than a quarter of healthcare expenditure is on the last year of a person’s life, with half of that during the last 60 days

• Families are more likely to be supporting older members

• Retired people comprise a growing market and companies/industries that accommodate the needs/wishes of older people will flourish

• Transport, housing, and infrastructure must be built or adapted

• Political power of older people (the ‘grey lobby’ in America) will grow

Successful versus unsuccessful ageing

How can success be defined, i.e. towards what aim should public health and clinical medicine be striving? The following definitions are, to some extent, stereotypical and culture-sensitive. More flexible definitions would acknowledge individual preferences.

• Successful ageing. Without overt disease, with good physical and cognitive function, a high level of independence, and active engagement with the broader society. Usually ended by a peaceful death without a prolonged dying phase

• Unsuccessful ageing. Accelerated by overt disease, leading to frailty, poor functional status, a high level of dependence, social and societal withdrawal, and a more prolonged dying phase where life quality may be judged unacceptable

Illness in older people

One of the paradoxes of medical care of the older person is that the frequency of some presentations (‘off legs’, delirium . . . ) and of some diagnoses (infection, dehydration . . . ) encourages the belief that medical management is straightforward and that investigation and treatment may satisfactorily be inexpensive and low-skilled (and thus intellectually unrewarding for the staff involved).

However, the objective reality is the reverse. Diagnosis is frequently more challenging, and the therapeutic pathway less clear and more littered with obstacles. However, choose the right path, and the results (both patient-centred and societal (costs of care, etc.)) are substantial.