With time, effects of diabetes on the cardiovascular system, the kidneys, the retina and the peripheral nervous system, often referred to as long-term complications of diabetes, substantially increase mortality and morbidity in older adults. In general, diabetes in older adults is under diagnosed and undertreated. A growing body of evidence assessing outcomes of interventions and an increasing number of therapeutic options for diabetes management have increased the importance of making a diagnosis and offering appropriate intervention strategies to older persons who have this potentially devastating disorder. Although the incidence of new-onset type 1 diabetes in older adults is very low, effective treatment of type 1 diabetes may prevent or delay the development of long-term complications and increased mortality. Thus, people who develop type 1 diabetes earlier in life may live to old age and therefore become a part of the spectrum of diabetes mellitus in an older adult population....
Approximately 90 per cent of older adults with diabetes have type 2 diabetes. Worldwide, type 2 diabetes is an important and common disease that is steadily becoming more common. In Europe, the USA and most westernized countries, type 2 accounts for up to 85 per cent of total cases of diabetes, and probably affects five to seven per cent of the population; it is likely that many cases (perhaps up to 50 per cent) are currently undiagnosed.1,2
The prevalence of type 2 diabetes is low (less than one per cent) in many developing societies and very high (40-50 per cent) in certain groups, e.g. the Pima Indians of Arizona and the Nauruans.2,3 Both of these societies have become westernized relatively rapidly during the last few decades, and this has been paralleled by an increase in the incidence of type 2 diabetes. Several key aspects of the westernized lifestyle ('coca-colonization'3) predispose to obesity, insulin resistance and type 2 diabetes, notably a high intake of energy-rich fatty foods and physical inactivity. The diabetogenic effects of westernization are also illustrated by the several-fold increases in the prevalence of type 2 diabetes seen in immigrant populations, such as Asians living in the UK or South Africa.3,4
Type 2 diabetes is predominantly, but not exclusively, a disease of the middle aged and elderly. In Europe and the USA, about 70 per cent of patients are over 55 years of age and the average age at diagnosis is 60 years. The prevalence of type 2 diabetes increases markedly with age in all populations, and in Europe and the USA it probably affects 10 per cent or more of those over 70 years of age. The true prevalence is difficult to judge because many cases have few or no symptoms in the early stages, and are therefore undiagnosed.5,6 Overall, there appears to be a male preponderance (approximately 3:2 males:females).
Type 2 diabetes is a very costly disease, in individual, social and economic terms. Although sometimes asymptomatic, it can cause the same microvascular and macrovascular complications as type 1. Accelerated and severe atherosclerosis is the major problem and results in much morbidity through angina, heart failure, claudication and stroke; myocardial infarction, often at a young age, is the most common cause of death in type 2 diabetes. Retinopathy, nephropathy and neuropathy can all affect patients with type 2 diabetes. It cannot therefore be regarded as 'mild' diabetes, even though blood glucose levels may be only moderately raised in many cases and patients will not die acutely if treatment is withdrawn.7
Institutionalized older adults with diabetes
Since diabetes is one of the commonest chronic diseases of older adults, one might expect a higher prevalence of diabetes and its complications in residential or nursing homes. Several US studies have found diabetes in 20 per cent of nursing home residents8 and in one study almost 90 per cent of diabetic residents had coronary artery disease, strokes or peripheral vascular disease, with 6.4 major diagnoses compared with only 2.4 in non-diabetic residents. In the UK, Sinclair et al.9 report an overall prevalence rate of 12 per cent for known diabetes, and 14.8 per cent for newly detected diabetes in care home residents. Looking at the patterns of care, levels of complications and resource usage of diabetic residents in residential or nursing homes in the UK, Benbow et al.10 surveyed 44 residential and nursing homes comparing residents with diabetes with age- and sex-matched controls. The provision of care for this vulnerable group of diabetic residents was found to be inadequate despite their high morbidity levels and greater use of health service resources. Many residents had no medical team responsible for their diabetic care and had not been assessed for the presence or risk of diabetic complications, emphasizing that diabetes care in institutionalized older adults is potentially a long neglected area.
4.2 The Ageing Process
There are currently over 57 million people resident in the UK. The relative proportion of elderly people (aged 65 years or over) in this population has increased considerably and the proportion aged over 80 years shows an even more dramatic rise. In the UK in 1971, 10.9 per cent of the population were aged between 65 and 79 with 2.3 per cent over 80. The number of people over pensionable age is projected to increase from 11.2 million in 2006 to 11.9 million in 2011, and will rise to 13.1 million by 202111 (Table 3.2). These trends are also reflected in other European countries. In the USA, 12.6 per cent of the population were aged 65 or over in 1990. This proportion is expected to rise to 22.9 per cent by the year 2050 with the over 85 year old group increasing by a factor of 3.9 in this timescale.12
Ageing has been defined '. . . as a process that converts healthy adults into frail ones, with diminished reserves in most physiological systems and an exponentially increasing vulnerability to most diseases and death'.13 It is difficult to distinguish between what constitutes natural ageing and what constitutes accelerated ageing due to disease processes among elderly patients. Cross-sectional studies, comparing findings in elderly people with those in younger people, have helped to highlight changes associated with the ageing process. In certain organs, such as the kidneys, a subgroup of people appear to experience a gradual decline in function over time, roughly a one per cent loss in function per year starting around the age of 30, while in others function remains constant well into old age.12 Such changes will obviously have a profound effect on drugs which are dependent on the kidney for elimination. Age-related changes in the eye including decreased pupil size and growth of the lens lead to decreased accommodation, acuity, color sensitivity and depth of perception, 12 which can lead to difficulties for older people in distinguishing between tablets that look similar.
It is important to note that ageing is a gradual process, with many changes commencing in early adulthood, although most do not manifest themselves until later life. In addition, not everyone ages at the same rate or in the same way. Frequently, the process of ageing only becomes apparent when a particular organ is subjected to external stress; for example, older people may often have a normal resting pulse but cannot sufficiently increase cardiac output to cope with exercise.
There is considerable debate about whether the age-related decline in insulin action, for example, is an effect of age per se or is secondary to age-related changes in body composition and physical activity. An absolute or relative increase of body adiposity, particularly central body adiposity, and an associated decrease of muscle mass can each contribute to insulin resistance. Similarly, it is well known that conditions associated with decreased physical activity are associated with insulin resistance and that exercise training can improve insulin sensitivity.
Thus, diminished physical activity in an older individual can also contribute to decreased insulin sensitivity. Both in animal studies and in humans, it has been difficult to demonstrate a residual effect of ageing on insulin action when the changes in body composition and physical activity are controlled for.
Coexisting illness can be another confounding factor affecting insulin sensitivity in an older person. Furthermore, any acute illness can precipitate hyperglycemia because of effects of stress hormones released during stressful illness to inhibit insulin secretion.
Ageing is further associated with a myth of gradual yet inescapable cognitive decline. It is well established that impairments in cognitive functioning are often seen with advancing age but that such a decline is not an 'all or none' phenomenon. That is, age does not seem to affect all areas of cognition and all older adults in the same way.14 For example, it is generally accepted that over-learned, well practiced, familiar cognitive skills (i.e. ones relying on crystallized intelligence) are likely to be spared, whereas activities requiring reasoning and complex problem solving (i.e. fluid intelligence) may well be affected by the ageing process.15
Next Week: Symptoms and their Representation/Clinical Features of Diabetes
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12. Kane RL, Ouslander JG, Abrass IB. Essentials of Clinical Geriatrics, 3rd edn. New York: McGraw-Hill, 1994.
13. Miller RA. The biology of aging and longevity. In Hazzard WL, Bierman EL, Blass JP, Ettinger WH, Halter JB, Andres R. (eds), Principles of Geriatric Medicine and Gerontology, 3rd edn. New York: McGraw-Hill, 1994 Chapter 1, pp 3–15.
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15. Lezak MD. Neuropsychological Assessment. Oxford: Oxford University Press, 1995.
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