When considering drug use among the elderly, it is helpful to consider substances of misuse in three broad categories: medications, both prescribed and non-prescribed; socially sanctioned psychoactive substances; and illicit substances. Self-evidently this classification will differ between countries due to religious, cultural and legal differences.3 Among the elderly, drugs from the medicines category are over-represented in people with harmful use when compared with other age groups.4 This reflects the increased access to medicines among this group, allied to the physical and social barriers that make accessing other drugs harder for this group.

This chapter focuses on drug misusers who display ‘harmful use’, which is defined as ‘a pattern of psychoactive drug use that causes damage to health, either mental or physical’.5 The damage may be physical (as in cases of hepatitis from the self-administration of injected psychoactive substances) or mental (e.g. episodes of depressive disorder secondary to heavy consumption of alcohol).6 It excludes cases where omission of a psychoactive medication may be harmful, for example, in cases of underuse of antidepressants.

While drug absorption shows little variation with age, ageing results in an increase in the percentage of body fat, a reduction in lean body mass and a fall in total body water. Hydrophilic drugs, such as alcohol, are distributed in body water, such that with increasing age the volume of distribution falls and the peak concentration for a given dose may rise by 20%,7 resulting in lower levels of intake giving the same intoxicant effect. Conversely, lipophilic drugs, such as benzodiazepines, that are stored in fatty tissue will remain in the body for longer, which could cause prolonged clinical symptoms such as disturbed cognition and mood.8 A fall in plasma albumin in old age results in increased bioavailability of protein-bound drugs, such as warfarin and diazepam.

Drug elimination, through direct excretion or metabolism, is reduced in the elderly. Glomerular filtration rates fall steadily in old age, leading to the accumulation of renally excreted drugs. This may be compounded by renal damage due to drug misuse, for example, analgesic abuse.9 Hepatic metabolism is reduced due to a reduced liver mass and blood flow, which may also be compounded by toxic drug effects. The efficiency of microsomal oxidation also falls with age, leading to reduced drug excretion of hepatically metabolized drugs.10 The combination of these effects may greatly alter pharmacokinetics in the elderly. For example, the half-life of diazepam in the very elderly has been shown to be over 3 days, compared with 20 h in younger subjects.11

Multiple drug use complicates the pharmacokinetics of a substance, due to competition for binding sites and metabolic pathways. Polypharmacy has different effects, depending on whether it is acute or chronic. Alcohol will inhibit microsomal enzyme activity in acute use, while prolonged administration will induce the same enzymes. Hence alcohol will acutely raise concentrations of benzodiazepines, while lowering them if used chronically.12

Pharmacodynamics also alter in the elderly. Few studies of age-related changes in the brain have focused on how these changes affect the function of the reward system and/or its sensitivity to drugs of abuse.13 There are documented changes in the neurotransmitter systems (dopaminergic, glutamatergic and serotonergic) in the ageing brain. There is a reduction in dopamine receptor binding in the striatum, frontal cortex, anterior cingulated gyrus, temporal insula and thalamus plus the same change in N-methyl-D-aspartate (NMDA)-type glutamate receptors in the cortex, striatum and hippocampus.13

The elderly may display harmful use of any psychoactive substance. Illicit drug use is not commonly observed in the elderly, but numbers are on the rise.14 Shah and Fountain identified the following as factors associated with illicit drug use in the elderly: male gender, ‘young old’ age group, belonging to the post-War cohort, African-American ethnicity, prior convictions, diagnosis of mental illness or alcohol misuse, serious medical illness and past history of substance misuse with onset before age of 30 years.15

Benzodiazepines are the most frequently abused prescribed medication in elderly people.16 Chronic use may contribute to toxic effects, including cognitive impairment, poor attention and anterograde amnesia, cerebellar signs such as ataxia,17 dysarthria, tremor, impaired coordination and drowsiness,18 depression and cognitive decline.13 Increased falls and hip fractures are associated with benzodiazepine use in the elderly.16, 19–21 The risk is especially high within the first few weeks of use.

Withdrawal may be accompanied by rebound insomnia, agitation, convulsions and an acute confusional state. If benzodiazepines are required for the elderly, then short-acting drugs (i.e. with half-life less than 24 h) at the lowest effective dose may be used for a short duration.22 There is no ‘safe’ period of use but tolerance and dependence levels increase with prolonged use.23

Prevalence of Benzodiazepine Use

Establishing levels of benzodiazepine amongst the elderly is problematic. National prescription audits can reflect trends in use but are unhelpful when considering particular population subgroups.

Following the publication of guidance for the appropriate use of benzodiazepines by the Committee on Safety of Medicines (CSM) UK in 1988,24 prescribing of benzodiazepines has fallen dramatically. In England and Wales, prescriptions fell by 32% from 1987 to 1996.25 Of concern, however, is that 30% of prescriptions were for long-term treatment and 56% of prescriptions for the three most commonly prescribed benzodiazepines were issued to patients over the age of 65 years.26

A community follow-up study of 5000 over-65s in Liverpool17 revealed that 10% were using benzodiazepines on first assessment and that of these about 70% were taking a benzodiazepine 2 years and 69% 4 years later. Women were twice as likely to be taking a benzodiazepine as men at any stage in the study. In the USA, a study found 6.3% of a large sample of over-65s used a hypnotic, one-third of these daily and nine-tenths for at least 1 year.27

Use of benzodiazepines in institutional cohorts has traditionally been higher and associated with female gender, greater age, bereavement and poor health.28 Chronic benzodiazepine use in older adults in nursing homes has been associated with depression, sleep disturbances and demand for medication.21 In the USA, a study found that one-quarter of nursing-home residents were prescribed a benzodiazepine and nearly 10% of all residents had chronic benzodiazepine use.29 Studies from other countries revealed similarly high levels of benzodiazepine use among institutionalized older adults.29

Psychiatric Morbidity

Significantly high rates of psychiatric disorder have been described among elderly benzodiazepine users.30 Benzodiazepine misuse happens in comorbidity with anxiety disorders31, 32 and affective and sleep disorders.32 The incidence of comorbid alcohol abuse has not been consistently shown to be significantly greater among benzodiazepine misusers.31 However, more recent research suggests that a prior history of alcoholism may predispose to later benzodiazepine misuse in the elderly.16 Benzodiazepines are also used to reduce the undesirable effect of those substances.32

An all-age study found that DSM-III-R Axis I comorbidity existed in all cases of a sample of benzodiazepine-dependent users in Spain.32 The commonest diagnoses were insomnia, anxiety disorders and affective disorders. Obsessive–compulsive, histrionic and dependent personality disorders were found in half of cases and physical problems in one-third of cases.

Depression can occur during the use and anxiety during the withdrawal. During use and withdrawal, some patients can suffer from psychotic episodes with hallucinations and delusions; nocturnal restlessness, paradoxical excitement and delirium.33 The risk of suicide also increases.8

Gender and Age

Benzodiazepine use is over-represented among women of all ages. The likelihood of use of a benzodiazepine increases with age. There is little evidence that this gender divide narrows on reaching old age. Legislative approaches and prescribing guidelines have made some inroads into the over-representation of prescribing to the elderly.34 Increasing public awareness of the side effects of benzodiazepines and an increase in advocacy services for the elderly are likely to have a similar effect.

Unfortunately, the prevalence of substance misuse in the elderly has not been investigated thoroughly, partly because substance misuse had not been considered to be a common health problem in this population. Overall, the prevalence of illicit drug use in the elderly is low compared with younger people.15

In the Epidemiological Catchment Area (ECA) Study, only 0.1% of elderly subjects met the criteria for drug abuse of an illicit substance in the previous month. Lifetime prevalence was 1.6% for over-65s.35 Figures from the 2005 and 2006 National Survey on Drug Use and Health found similar low rates in the elderly along with higher rates in the middle aged, lending further evidence to the suggestion that prevalence rates may rise in the elderly as the younger cohort ages.36 It has been estimated that as the baby boom generation reach older age, the number of elderly drug users will also increase in the Western world. Gfroerer and co-workers predicted that, compared with 2000, by 2020 there will be a 50% increase in number of older adults and a 70% increase in treatment need among them.14 These predictions were replicated in other studies.37

In the UK, few cases of illicit drug use among the over-65s have been reported in the literature; one exception is a series of seven elderly subjects reported to have initiated injecting heroin in later life. They attributed their behaviour to a combination of loneliness and depression.38

In the USA, in a study of a Veterans’ Administration old age psychiatry inpatient facility, 3% of the patients were found to have a primary drug misuse disorder involving prescribed medication, while 1% were addicted to illicit substances.16 Also in the USA, attendance at methadone maintenance clinics by the elderly is reported to be rising, although over-60s still form only 2% of those attending.4 Similarly, a number of elders are reported to continue their use of cannabis into late life.39

Explanations for the lower prevalence of drug misuse among the elderly include increase mortality among younger substance misusers, maturation out of substance misuse habit, poor identification of elderly cases and low acceptability of substance misuse among elderly people.15

There is a significant difference between the elderly drug user and the younger generation which leads to further marginalization of this group. The concept of marginality is introduced in this context to describe this group who live at the periphery of two cultures and do not belong to either, that is, they are marginal among a marginal group.40