Review: Xerostomia: A symptom which acts like a disease

Age and Ageing,  Sept, 1996  by Ronald L. Ettinger

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Saliva is one of the most complex but versatile and important body fluids and contains a number of systems which serve a wide spectrum of physiological needs. Saliva is required to swallow food, to speak and to protect the oral mucosa and the teeth from infection. This fluid contains a variety of electrolytes, peptides, glycoproteins, and lipids which have:

(a) antimicrobial properties to kill bacteria and viruses,

(b) mucins to coat and protect the mucosa from trauma and dehydration

(c) buffers to maintain pH levels in spite of the daily use of acidic and basic foods and fluids,

(d) calcium and phosphates which protect the teeth and prevent demineralization and dissolution of the teeth within the oral cavity [1-3].

A loss or reduction of saliva results in significant problems such as caries, periodontal diseases, difficulties with denture wearing, eating, talking, altered taste sensation, as well as higher risks of candidiasis and mucositis, which result in an overall reduction in the quality of life [4-7].

Sreebny [8] has defined xerostomia as the 'subjective feeling of oral dryness' and it is the result of salivary gland hypofunction. This symptom is more common in ageing populations, but is not caused by ageing. It has been shown to be related to some specific drugs and diseases or therapies [9-16]. The prevalence of xerostomia varies from 13 to 28% in most older populations (Table I) and increases up to 60% in patients living in long-term care facilities [12-17].

Table I. Prevalence of xerostomia

Reference      No.       Age (years)          Population
12            1148       70                      Ind
13             154       64+                     Int
14             259       60+                     Ind
15             157       86.6 [+ or -] 5.6       Int
16             149       71 - 99                 Int
17             907       63 [+ or -] 8           Ind

               Percentage with hypofunction

Reference      Men       Women     All
12             16.0      25.0      21.0
13             52.0      27.0      42.0
14             27.3      28.3      27.7
15             --        --        61.0
16             37.0      60.0      48.6
17             13.8      20.7      17.7

Ind = independent or community living. Int = institutionalized or nursing-home population.

The rate of salivary secretion is related to incidence of disease and the rate of secretion is further diminished with an increase in the number of diseases. Although reduced salivary flow is an age-related change, xerostomia is not likely to occur unless the patient's health is compromised by diseases and the drugs used to treat these diseases [18, 19]. The older the patients, the more likely they are to have some form of disease or to be taking medications which might have a xerostomic potential [12-18].

Mason and Glenn [20] have stated that as the secretion of saliva is regulated by the autonomic nervous system and is subject to reflex stimulation from physical and psychic causes, then xerostomia may result from four basic causes:

A. Factors affecting the salivary centre:

1. Emotions--fear, excitement, stress

2. Depression

3. Organic disease, e.g. brain tumour, Parkinson's disease

4. Drugs, e.g. levodopa, morphine.

Of these factors [21-26], depression is the most important, for its incidence increases greatly in ill and dependent old people.

B. Factors affecting the autonomic outflow pathway:

1. Encephalitis

2. Brain tumours

3. Stroke

4. Neurosurgical operations

5. Drugs.

There are over 400 drugs which older people take to control some of the diseases they have acquired, which have anticholinergic properties and dry out the mouth [27-32]. The most common groups are: antidepressants, antihistamines, antiparkinsonian drugs, diuretics, antipsychotics, antihypertensives, anticholinergics, and antineoplastic agents.

Drug-related changes vary in intensity from person to person [4, 32]. In dentate persons, the caries risk--especially root surface caries--will depend upon the duration of administration of the drug, the person's susceptibility to caries, the degree of dietary alteration, the severity of the xerostomia the drugs produce, as well as the effectiveness of the person's oral hygiene regimen. Root surface caries is decay which occurs on the exposed roots of the teeth after periodontal disease or gum disease has caused bone loss and exposure of the root surfaces to the oral environment. These root surfaces are at a higher risk to become decayed because their chemical structure has less mineral contents than enamel. The consequences are that these lesions can be very hard to restore adequately and can result in loss of the natural teeth. For elderly people, neuromuscular co-ordination becomes a major factor in the ability to maintain an adequate level of oral hygiene. If oral side-effects are noticed, it may be possible for a dentist to ask the patient's physician either to adjust the drug dosages, to modify the drug schedules, to change drugs, or to treat the induced xerostomia jointly [4].