Disease Prevalence and Drug Use in the Elderly

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Chapter: Pharmacovigilance: Drugs and the Elderly

The prevalence of many diseases is age related and several may co-exist in the same patient.


DISEASE PREVALENCE AND DRUG USE IN THE ELDERLY

The prevalence of many diseases is age related and several may co-exist in the same patient. These include hypertension (Hawthorne, Greaves and Beevers, 1974), osteoarthrosis (Lawrence, 1977) and prostatic hypertrophy (Berry et al., 1984). Age-specific mortality rates for cardiovascular and cere-brovascular diseases, together with data for cancers, are shown in Table 42.1 (British Heart Foundation, 2000) and morbidity data in Table 42.2 (British Heart Foundation, 2001).


Cardiovascular and cerebrovascular problems related to atheroma are the most common causes of death in the elderly and are also a major source of suffering. Nevertheless, a huge majority of old people have osteoarthrosis of the joints and the lower limbs (Blackburn et al., 1994) causing pain and disability without threatening life.

Several studies have examined the nature and preva-lence of medicines prescribed for old people living in the community. One of the best known is that by Cartwright and Smith (1988) which was based on a random sample of people aged 65 and over drawn from the electoral registers of 10 parliamentary constituencies in England. Information was obtained from 805 patients (78%) of the 1032 included in the original sample. Of these 805 patients, 60% had taken one or more prescribed medicines within the preceding 24 hours. Drugs for the diseases of heart and circulation were widely prescribed, and diuret-ics formed a therapeutic category in most widespread use. Diuretics were followed by analgesics, hypnotics, sedatives and anxiolytics, drugs for rheumatism and gout and then -adrenoceptor antagonists. Similar findings were recorded in two studies from Southamp-ton (Ridout Waters and George, 1986; Sullivan and George, 1996). A review by Jones and Poole (1998) confirmed the rising use of cardiovascular drugs amongst elderly people and widespread use of agents with an effect on the central nervous system. There was, however, some geographic variation in the use of medicines for musculo-skeletal and joint disease. By contrast, the use of drugs with an action on the central nervous system varies according to individual circumstances: psychotropic agents are used particu-larly in patients in residential nursing homes and in long-term care (McGrath and Jackson, 1996). A recent investigation, however, has shown that medication undertreatment is a problem of equivalent magni-tude to that of medication overuse in long-term care settings of elderly residents (Sloane et al., 2004). Overall, the use of prescription medications by older persons is increasing rapidly both to treat a large range of diseases as well as non-disease-specific symptoms.

Besides prescribed medicines, elderly people as a group are high consumers of non-prescription medi-cation. Indeed, it has been estimated that over 50% of elderly people take one or more over the counter (OTC) preparations every day (Chrischilles, Segar and Wallace, 1992b). Those OTCs most commonly taken are oral analgesics, vitamins and tonics, but recently, the popularity of herbal medicines has increased (Barnett, Denham and Francis, 2000). Women are particularly likely to consume OTC medicines and some of these can interact with prescription medicines to cause adverse events.

There are two other features which are character-istic of drug therapy in the elderly: long duration and polypharmacy. Drug treatment for older people is often for chronic conditions, which means that once started, medicines tend to be continued for 6 months or longer (Ridout Waters and George, 1986). This may account for the increased rates of gastroin-testinal bleeding in patients taking non-steroidal anti-inflammatory drugs (NSAIDs) (Langman et al., 1994). This latter problem highlights the need for improve-ments in repeat prescribing and for regular review of medication in the elderly.

POLYPHARMACY

There are several legitimate reasons for polypharmacy in the elderly. First, as indicated previously, the preva-lence of many diseases is age related and several may co-exist in the same patient. Secondly, it may not be possible to achieve an adequate therapeutic response from the use of a single drug. There is an increas-ing promotion of therapeutic regimens, including two or more drugs used in combination for the optimum management of a number of conditions including diabetes, heart failure, hypertension and ischaemic heart disease (Gurwitz, 2004). A third reason for giving more than one drug simultaneously is to coun-teract or minimise the risk of side effects (type A adverse reaction) occurring. The difficulty with this approach is that adverse drug effects may be misinter-preted as a new medical condition and another drug is prescribed to treat the observed effects leading to a ‘prescribing cascade’ (Rochon and Gurwitz, 1997). Finally, patients are also being targeted by pharmaceu-tical companies in the so-called direct-to-consumer advertising, which is likely to have the effect of increasing polypharmacy in older people.

In the study by Cartwright and Smith (1988), the average number of medicines prescribed for the patient was 2.8, but many patients living in the community received more than this. In an American telephone survey of non-institutionalised ambulatory adults, the highest overall prevalence of medication use was in those over 65 years, of whom 12% took at least 10 medications (including prescription, OTC and herbal treatments) during the preceding week; and 23% of females and 19% of males had used five or more prescription drugs over the same time (Kaufman et al., 2002). Such polypharmacy can cause confu-sion leading to errors in medicine taking, particularly amongst those over the age of 85 (Parkin et al., 1976; Vestal, 1978).

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