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Caffeine addiction and its effects

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VOL: 97, ISSUE: 31, PAGE NO: 42

Simon Joseph, BSc, RMN, is a staff nurse, Oakwood House, Blackberry Hill Hospital, Bristol

The popularity of coffee, tea, cola and chocolate make caffeine the most extensively used stimulant in the world (Shapiro and McCall-Smith, 1997). It affects every cell in the body and makes people more active (Kolb and Whishaw, 1996).

Nurses in all areas need to be aware of how caffeine affects people and the wide range of symptoms with which it can present, including irritability, panic, drowsiness and seizures.

How caffeine works

Caffeine is found in more than 60 plant products, including tea, coffee and kola nuts. It stimulates the heart and increases tension in the skeletal muscles while relaxing smooth respiratory muscle (Groves and Rebec, 1992).

Caffeine acts in two main ways: stimulating cellular metabolism and mimicking neurotransmitters to stimulate the brain and nervous system. This increases alertness, staving off the effects of fatigue and sleep deprivation. For this reason it is often used by shift workers and those who are chronically deprived of sleep (Shapiro and McCall-Smith, 1997).

But it is physically addictive, producing tolerance and unpleasant withdrawal effects, and there is a need to evaluate the role it plays in some presenting symptoms. It is recommended that nurses promote moderation in the use of products that contain caffeine, with a gradual reduction rather than sudden cessation.

Dosages

It is not possible to predict the stimulant effect of caffeine because the amount contained in individual drinks varies widely. A cup of coffee will contain 100-200mg, while tea and cola contain 50-75mg (Table 1).

The half-life of caffeine, which is an indicator of the time it remains in the body, varies from three to seven hours. After ingestion, it reaches peak plasma levels in 15 to 45 minutes (Shapiro and McCall-Smith, 1997).

Caffeine affects people in different ways as its potency depends on each person’s usual consumption and age. It tends to be more potent and has a longer half-life in older people (Oswald and Adam, 1983). For these reasons, the amount consumed is not a reliable indicator of its stimulant effects.

Acute high doses

There is a condition known as caffeinism or caffeine intoxication (Pasquali et al, 1989). Its symptoms are anxiety, psychomotor agitation, tinnitus, insomnia and, occasionally, panic attacks (Carson and Arnold, 1996).

These can occur as a result of doses as low as 250mg, the equivalent of drinking two cups of strong coffee, in people who are particularly sensitive or already anxious. Even those who are not vulnerable can succumb with doses of about 500mg (Pasquali et al, 1989).

Mental health nurses therefore need to be aware of patients’ caffeine consumption if they are to treat anxiety disorders, including panic attacks, effectively. General nurses and doctors should also be aware that chronic, severe overdose can lead to cardiac arrhythmias, tonic-clonic seizures and even respiratory collapse (Carson and Arnold, 1996).

Tolerance and withdrawal

Caffeine is physically addictive. It results in tolerance, requiring progressively higher doses to produce an effect, and people experience the effects of withdrawal after chronic use (Carson and Arnold, 1996). A day of unusually high consumption may result in a withdrawal headache that could last as long as three days (Sutcliffe, 1991). Complete withdrawal can result in up to six weeks of depression, headache, irritability and drowsiness.

Mental health nurses who try to reduce patients’ anxiety by encouraging them to exclude caffeine from their diets may inadvertently generate the symptoms of depression.

Caffeine produces tolerance and causes withdrawal symptoms because the body’s excitatory nerves and endocrine glands compensate for their potentiation by producing progressively lower amounts of the catecholamine neurotransmitters and hormones (Merkley, 1993).

Sleep

Like other stimulants, caffeine is a powerful sleep inhibitor. By stimulating the central nervous system and increasing alertness, the onset of sleep (latency) is delayed and subsequent sleep is lighter and shorter (Shapiro and McCall-Smith, 1997). Its half-life of three to seven hours makes it advisable for susceptible patients to avoid drinking caffeine in the afternoons and evenings. About 60% of night-time panic attacks and nightmares are linked to caffeine consumption (Carson and Arnold, 1996).

Conditions influenced by caffeine

Caffeine can cause or exacerbate premenstrual syndrome (Carson and Arnold, 1996), so nurses and doctors in primary care should recommend a reduction in intake. It can also exacerbate tinnitus, especially in high doses.

Caffeine is a weak diuretic because it promotes the production of urine (Smith, 1986), which could be detrimental to the quality of a patient’s sleep.

Eliminating caffeine from the diet

Encouraging moderation is more effective and less damaging than persuading the patient to cut out caffeine completely. An initial daily limit of 800mg is the most effective strategy (Smith, 1986), and patients who are not able to sleep at night should be advised to avoid it after 6pm.

If patients want to exclude caffeine from their diet, a gradual reduction over several weeks or months should be recommended, with the morning dose the last to go. It is a good idea to warn them about the signs of withdrawal so that they can avoid them by weaning themselves off caffeine in stages.

Some patients prefer to mix caffeinated and decaffeinated coffee, gradually increasing the proportion of decaffeinated coffee. People who prefer to stop suddenly should be offered positive encouragement when they are feeling irritable.

Conclusion

To enable nurses to assess patients accurately and meet their needs, particularly in view of the widespread use of this stimulant, it is important for them to be aware of the potential effects of caffeine.

In moderation, it can be used as a short-term stimulant to improve performance that is impaired because of unavoidable sleep deprivation. But it may be the underlying cause of a number of symptoms (Box 1).

When adopting a health promotion role, it is most beneficial to initially recommend moderation (up to 800mg a day), with little after midday, rather than an immediate cessation of caffeine.

- Further information can be found at:

www.drugshouse.org.uk/history/

www.indwes.edu/faculty/bcupp/things/thought1.htm#coffee

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