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Australian Dental Journal

The official journal of the Australian Dental Association

Australian Dental Journal 2015; 60:(1 Suppl): 54–63 doi: 10.1111/adj.12284

Dry mouth and older people WM Thomson* *Department of Oral Sciences, Sir John Walsh Research Institute, School of Dentistry, The University of Otago, New Zealand.

ABSTRACT Dry mouth is more common among older people than in any other age group. Appropriate definition and accurate measurement of dry mouth is critical for better understanding, monitoring and treatment of the condition. Xerostomia is the symptom(s) of dry mouth; it can be measured using methods ranging from single questions to multi-item summated rating scales. Low salivary flow (known as salivary gland hypofunction, or SGH) must be determined by measuring that flow. The relationship between SGH and xerostomia is not straightforward, but both conditions are common among older people, and they affect sufferers’ day-to-day lives in important ways. The major risk factor for dry mouth is the taking of particular medications, and older people take more of those than any other age group, not only for symptomatic relief of various age-associated chronic diseases, but also in order to reduce the likelihood of complications which may arise from those conditions. The greater the number taken, the greater the associated anticholinergic burden, and the more likely it is that the individual will suffer from dry mouth. Since treating dry mouth is such a challenge for clinicians, there is a need for dentists, doctors and pharmacists to work together to prevent it occurring. Keywords: Dry mouth, medications, older people, xerostomia. Abbreviations and acronyms: AID = Automatic Interaction Detection; OHRQoL = oral health-related quality of life; SADLS = South Australian Dental Longitudinal Study; SGH = salivary gland hypofunction; SSFR = stimulated salivary flow rate; SXI = Summated Xerostomia Inventory; USFR = unstimulated salivary flow rate; VAS = visual analogue scale; XI = Xerostomia Inventory.

INTRODUCTION Dry mouth is a surprisingly common condition which can have a devastating effect, not only on sufferers’ dentitions, but also on their day-to-day lives.1,2 Saliva has been described as ‘lacking the drama of blood, the sincerity of sweat and the emotional appeal of tears’,3 yet its chronic absence has a profound impact. Dry mouth is particularly prevalent among older people, and it is well worth spending some time considering the condition. Before describing, studying, reporting on and treating dry mouth, we need to adequately define and measure it. Only then can its occurrence and risk factors be determined. What is dry mouth? On the face of it, this seems like a silly question. As undergraduates, most dentists were taught that dry mouth was invariably the result of low salivary flow; that is, that every patient who complained about having a dry mouth would have a flow rate which was considerably lower than normal (whatever ‘normal’ was understood to be). Similarly, every patient with a demonstrably low salivary flow would be sure to be 54

complaining about having a dry mouth. This notion was partly due to the absence of information to contradict such a simplistic assumption, and partly due to the profession taking a largely mechanistic, positivist view of oral conditions which relied almost entirely upon visual diagnosis. An experiential approach – whereby patients are asked about their symptoms – was viewed by most as lacking validity or reliability; patients couldn’t be trusted to be reliable observers of their own health states. Thus, an objective measure of salivary flow was seen as a better way through which to label someone as a dry mouth sufferer than actually asking that individual whether they suffered from dry mouth. Interestingly, this began to change during the late 1980s and early 1990s, when growing awareness of the usefulness of self-report information (and a formal framework through which to use it) led to the development of a number of scales to measure what is termed oral health-related quality of life (OHRQoL).4–6 The side-by-side collection of both self-report and clinical data in oral health research rapidly became the norm, rather than the exception. That particular development had a profound impact upon our understanding of dry mouth. Up to the early 1990s, only two studies had reported on both flow © 2015 Australian Dental Association

Dry mouth and older people rate and self-rated dry mouth among population samples of older people,5,6 but neither of those investigated whether the people with low flow rate were the same individuals complaining about dry mouth. A study of 1148 70-year-old Swedes7 measured dry mouth symptoms in all of them, but salivary flow rate was determined only in a small subsample (N = 111). Among the latter, women reporting subjective dryness had lower mean unstimulated salivary flow rates. However, doubts remain about the validity of the question used to measure dry mouth in that study.8 A turning point in understanding came when an epidemiological study of older South Australians found that approximately one in five had either xerostomia or SGH, but that the two conditions coincided in only one-sixth of those with either condition, or in about 6% of the overall sample.9 This was the first empirical evidence to suggest strongly that xerostomia and SGH are not necessarily concurrent. Thus, it is now understood that dry mouth can have two possible manifestations, one of which is a symptom, the other a sign. Xerostomia is the subjective feeling of dry mouth, measurable only by directly questioning individuals.10 On the other hand, people with salivary gland hypofunction (SGH) have lower-than-normal salivary output (flow rate); it must therefore be determined by sialometry.11 It appears that a relatively small proportion of dry mouth sufferers have both conditions. Understanding the innervation of the salivary glands and the physiology of salivary flow is essential for an appreciation of dry mouth and its risk factors. The autonomic nervous system plays an important role in salivation, with the glands having both sympathetic and parasympathetic innervation. Salivation is mainly under parasympathetic control from salivary nuclei in the brainstem, pons and medulla. Sympathetic stimulation will also cause salivation (via adrenergic stimulation), but the resultant saliva differs from that arising from parasympathetic (cholinergic) stimulation. b-adrenergic stimulation leads to saliva which is of low volume and high viscosity with a very high mucin concentration; a-adrenergic stimulation also produces low-volume, high-viscosity saliva, but with a low mucin concentration. Cholinergic stimulation results in high-volume, low-viscosity saliva with low concentrations of protein and mucin.12 This means that, in theory at least, sustained b-adrenergic stimulation by b-adrenergic agonists (such as the bronchodilators used in asthma treatment) could lead to viscous saliva which is of relatively low volume, and that could lead to the symptoms of dry mouth without a detectable effect on actual salivary flow rate. More consistent with current understanding, anticholinergic drugs can act to reduce salivary flow, and this appears to be greater with chronic exposure. Chew and co-workers13 intro© 2015 Australian Dental Association

duced the useful concept of the overall anticholinergic burden: other factors being equal, the greater the number and dosage of anticholinergic drugs being taken, the greater the likelihood and severity of side effects such as dry mouth. This would account for the common observation that those taking a large number of medications have higher rates of dry mouth irrespective of the actual preparations being taken. Measuring dry mouth It is important to be specific when describing the occurrence of dry mouth – whether in a patient or in a population – and it is vital that whichever aspect being investigated is measured properly (Table 1). Arriving at a diagnosis of SGH requires measurement of salivary flow, after which the flow rate is compared against a reference value or threshold; those with a salivary flow rate below that particular reference value are deemed to have SGH. On the other hand, arriving at a xerostomia diagnosis requires that the individual be asked about their symptoms of dry mouth. A useful comparison which helps to understand the latter concept is with headache: a clinical examination will not reveal whether someone has a headache; the clinician must ask the patient whether they have one. Similarly, determining whether a patient has xerostomia requires that we ask about it. Each of these approaches – measuring salivary flow and asking about symptoms – appears to be straightforward on first consideration, but there are challenges specific to each. These are considered below. Sialometry Measuring salivary flow rate with an acceptable degree of validity and reliability is challenging. First, there is a choice between measuring the unstimulated salivary flow rate (USFR) or the stimulated salivary flow rate (SSFR). Both can be measured, of course, but the former must be done first, otherwise the risk is that ‘carry-over’ stimulation of the salivary system will result in overestimation of the USFR. Second, salivary flow can be measured by collecting saliva from either individual salivary glands (or pairs of glands), or the entire mouth. The latter is known as ‘whole saliva’ (as opposed to ‘glandular saliva’). Measuring it is simpler and more common than determining the flow rate of specific salivary glands. Anyone who has had a salivary gland cannulated will tell you that it is far from pleasant, and it is not possible to collect anything other than stimulated flow in such a situation. It should be remembered that whole saliva is a better representation of the in vivo situation;14 as such, it is clinically relevant, in terms of both the cariesprotective and lubricating functions of saliva and 55

WM Thomson what is understood to be the multi-glandular nature of SGH. There is little justification for collecting anything other than whole saliva in the clinical setting. The four methods for collecting whole saliva are termed the ‘drain’, ‘spit’, ‘suction’ and ‘swab’ methods.14 All require the collection of saliva over a predetermined time (usually 3 or 4 minutes), after which its volume is determined and a per-minute flow rate calculated by dividing the volume by the collection time. The ‘drain’ method requires the patient to allow saliva to passively drain into a receptacle. The ‘spit’ method requires the patient to allow saliva to accumulate in the oral cavity and then void it into a receptacle. In the ‘suction’ method, a suction tube is used to collect saliva from the floor of the mouth. The ‘swab’ method uses preweighed swabs (such as dental cotton rolls) which are placed on the floor of the mouth and allowed to collect saliva, after which they are weighed and the salivary flow computed. Neither of the latter two methods is suitable for determining USFR, because the collection process is itself likely to stimulate salivary flow. The ‘swab’ method is the least valid or reliable.14 Patients find the ‘spit’ method to be the most acceptable; by contrast, they find the ‘drain’ method to be rather unpleasant. No-one enjoys drooling passively into a container for a few minutes. Irrespective of the method used, the mouth should be rinsed with water some minutes prior to collection in order to rid it of residues from recent intakes (whether food or tobacco smoke) which may act to stimulate flow. After rinsing, the patient should sit quietly and wait for some time before undergoing the saliva collection. Once the saliva has been collected, its volume should be determined as soon as is practicable. This can be done either volumetrically or gravimetrically. The former can be problematic and prone to error because the presence of bubbles makes it very difficult to see exactly what the fluid level is. The latter is more valid and reliable, and it involves weighing the sample, and then converting the weight to a volume estimate. It is essential to preweigh the containers and mark the baseline weight of each (including its lid and the label) on its label. Other details to be recorded are: patient identification details; the date and time of sampling; and the duration of saliva collection (to the nearest second). The rationale for individual preweighing comes from experience in the South Australian Dental Longitudinal Study,15 where it was found that, while the mean overall weight of containers was 8.63 g, those weights ranged from 8.53 g to 8.80 g. Moreover, the distribution of container weights was bimodal, suggesting that they came from two different batches. Failing to preweigh them would have introduced an error of up to nearly 0.1 ml/minute in the 56

estimates of salivary flow; this would have severely compromised the study’s findings. If stimulated salivary flow rate is to be determined, it is necessary to stimulate flow using either gustatory or masticatory stimuli. An example of the former is a 2% solution of citric acid; this can be either dropped directly or applied on blotting paper to the dorsum of the tongue. Examples of masticatory stimuli are paraffin wax or pre-softened polyvinyl acetate gum; these have a neutral taste and are chewed in order to stimulate salivary flow. Another important consideration when measuring salivary flow is the time of day when it is done. Dawes’ seminal work four decades ago highlighted the existence of diurnal variation in flow.16 He studied eight people over periods ranging from 4 to 26 days, and demonstrated circadian rhythms in salivary flow rate (and composition). He observed that the highest USFR occurred in the late afternoon, and the lowest during the dead of night. Thus, if the stability of a patient’s salivary flow is to be monitored over time, each measurement should be done at approximately the same time of day. Measuring xerostomia By definition, measuring symptoms requires asking the individual; self-report is the only method available. Asking about dry mouth symptoms can be done by using a single question (known as a ‘global item’), or by using any one of a number of multi-item methods. Each of these is considered briefly below. The single-item approach involves a single question or statement which requires the individual to integrate their perceptions, experiences and behaviours in respect of the entity being measured and arrive at an overall summary judgement. Thus, a global item on dry mouth requires the individual to consider all of those aspects of the condition in order to arrive at a summary judgement of their dry mouth status. A wide range of these have been used, and not all are useful; some appear to lack validity.8 The most useful one which has been used is that first reported in 1993:17 ‘How often does your mouth feel dry?’ (response options ‘Never’, ‘Occasionally’, ‘Frequently’ or ‘Always’). Someone reporting dry mouth ‘Frequently’ or ‘Always’ – or whose mouth usually feels dry – is likely to be a chronic sufferer of the condition and is therefore determined to be xerostomic. The global item approach to measuring xerostomia can be very useful, providing that an appropriate item is used. It is also a useful validity check when used alongside a multi-item method (described below). Multi-item approaches to measuring xerostomia include both (a) batteries of items and (b) summated rating scales. Each will be described briefly. With item © 2015 Australian Dental Association

Dry mouth and older people batteries, participants respond to each item in a list, and those usually have a simple ‘yes’/‘no’ response format. The number of positive responses to the items in the battery is counted and used as an index score, either as a simple count or after recoding the count into ordinal categories (such as ‘0’, ‘1 to 2’, ‘3 or more’). A well-known example is a study of Canadian nursing home residents18 which used a seven-question battery and a simple ‘yes’/‘no’ response format to assign participants to the following three groups: no xerostomia (0 positive responses); mild xerostomia (1 to 2); or marked xerostomia (3 to 7). The battery’s properties were found to be acceptable, but there was no comparison with a global xerostomia item, meaning that no judgement of its validity as a xerostomia scale could be made (see below). A modification of that approach used an eight-item battery with each scored using a visual analogue scale (VAS).19 It is, if anything, more restricted in its use because the individual item scores are not used together. Battery-type approaches can provide useful data for investigating the occurrence of xerostomia, but they suffer from the problem of being really just arbitrarily-determined ‘present/absent’ checklists of items or issues which

Table 1. Overview of xerostomia and salivary gland hypofunction Aspect of dry mouth Xerostomia Domain Measurable features Measurement options

Symptom(s) Experiential aspects Behavioural aspects Single-item Multi-item methods Batteries of items Summated rating scales

Salivary gland hypofunction Sign(s) Salivary flow rate Stimulated flow Unstimulated flow Whole salivary flow Glandular salivary flow

may or may not adequately represent the experience of dry mouth. They have no sound psychometric underpinning. Summated rating scales have distinct advantages over batteries. A summated rating scale is a multiitem scale which purports to measure an underlying construct, or ‘latent variable’ (such as xerostomia). The items have all been shown empirically to be correlated with the latent variable. Such scales place respondents on a continuum representing the range of experience of xerostomia (from the minimum to the maximum), and everyone is able to be placed somewhere on that continuum. This allows the exploration of subtle differences in xerostomia because the data are used as a continuous variable rather than as a binary (‘xerostomic’/‘not xerostomic’) or ordinal (‘severely xerostomic’/‘moderately xerostomic’/‘not xerostomic’) variable. The most widely used such summated rating scale is the Xerostomia Inventory (XI),20 an 11-item scale (Table 2) developed in Australia during the mid1990s as part of an investigation into the question of whether medications which cause dry mouth (xerogenic drugs) among older people are associated with greater caries experience. It was needed so that participants could be placed on a continuum of symptom experience which could represent more subtle interpersonal differences in the symptoms of dry mouth than could be done with a global item. The XI’s development involved a systematic series of steps involving item pool generation (from a literature review and interviews with sufferers), and then fieldtesting in the South Australian Dental Longitudinal Study (SADLS), a prospective cohort study of oral health among older people.21 Data analysis identified 11 experiential and behavioural items which appeared to represent the underlying latent construct of xerostomia. Confirmation of its validity was undertaken, and it has since been validated in a number of differ-

Table 2. The available versions of the Xerostomia Inventory Original version (XI) Item content

Response options Possible score range

I sip liquids to aid in swallowing food My mouth feels dry when eating a meal I get up at night to drink My mouth feels dry I have difficulty in eating dry foods I suck sweets or cough lollies to relieve dry mouth I have difficulties swallowing certain foods The skin of my face feels dry My eyes feel dry My lips feel dry The inside of my nose feels dry ‘Never’ (scoring 1), ‘Hardly ever’ (2), ‘Occasionally’ (3), ‘Frequently’ (4), or ‘Always’ (5) 11 (no xerostomia) to 55 (worst possible xerostomia)

© 2015 Australian Dental Association

Short-form version (SXI-D) My mouth feels dry when eating a meal My mouth feels dry I have difficulty in eating dry foods I have difficulties swallowing certain foods My lips feel dry ‘Never’ (scoring 1), ‘Occasionally’ (2), ‘Often’ (3) 5 (no xerostomia) to 15 (worst possible xerostomia) 57

WM Thomson ent studies internationally. A now substantial body of published evidence indicates that researchers and clinicians can be reasonably confident in its ability to place people accurately on a continuum ranging from no xerostomia symptoms at all to the worst possible symptoms. The XI now has a short-form version (Table 2), the SXI (‘Summated Xerostomia Inventory’.22 It came about when Dutch researchers who wished to use the XI in a nursing home sample were worried about its response format and the inclusion of some superfluous item content (such as dryness of the facial skin).23 They reduced it to five items and collapsed the number of response options from five to three (‘Never’, scoring 1; ‘Occasionally’, 2; and ‘Often’, 5). It worked well in that study, and so an international team investigated the validity of the SXI in Japanese, Australian and New Zealand samples, along with the original Dutch one. The new measure performed very well and is now available as a short-form alternative, so far validated in English, Dutch, Japanese21 and Chinese.24 It is prudent to measure both salivary flow and xerostomia if possible. This holds for the clinical situation just as much as it does for research into dry mouth. The choice of salivary flow measurement (stimulated or non-stimulated, whole or glandular) depends upon the patient’s needs (in the clinical situation) or the research question being investigated (in the research setting). Those measuring xerostomia should plan the concurrent use of a single item and a summated rating scale (such as the SXI), so that the former can be used as a validity check for the latter, as well as assisting in the interpretation of scale scores. The prevalence and impact of dry mouth Making generalizations about the prevalence of dry mouth with any degree of confidence is a difficult task, not because of a lack of reports from epidemiological studies, but because of differences among those studies in measurement, case definitions and sample characteristics. There is also the issue of whether xerostomia or SGH was investigated. Consequently, the range of reported estimates is wide; for example, estimates of xerostomia prevalence from studies of representative samples of older populations range from 12% to 39% (with a weighted average of about 21%). Estimates of SGH prevalence among older adults show a much wider range (from 5% to 47%), with this variation reflecting the use of different approaches and case definitions.8 Variation notwithstanding, what those estimates underline is that dry mouth is common among older people, and more so than among younger people. Indeed, most epidemio58

logical studies of the condition have been undertaken using samples of older adults, with only two reports from younger adults.25,26 The latter showed that the prevalence was about half that seen in older populations. Although comparing epidemiological estimates from studies of older populations is complicated by the abovementioned inconsistencies in measurement, case definitions and approaches, it is possible to conclude that about 1 in 5 older people suffers from dry mouth.27,28 The impact of dry mouth upon sufferers has been shown to be considerable, whether it has been investigated among older adults18,29,30 or younger adults.31 Interestingly, a strong association between dry mouth and quality of life observed among older Japanese32 was detectable with either xerostomia or SGH, suggesting that both aspects of dry mouth are important influences on quality of life. Xerostomia sufferers may have problems while eating, speaking, swallowing or wearing dentures. People with hyposalivation have difficulty in masticating and swallowing (particularly dry foods), and they may need to sip liquids while eating. There may also be taste alterations, since saliva is a key component in the gustation process.33 The halitosis, burning mouth and tongue, and intolerance to acidic and spicy foods observed in sufferers of dry mouth34 can lead to changes in food and drink intake that can (in turn) adversely affect nutritional status and quality of life. A lack of saliva in the denturemucosa interface can produce denture sores, and prosthesis wearing can be difficult. This can in turn also affect food choices. While speech and eating difficulties are perhaps most obvious in those who have undergone radiotherapy for head and neck cancer,35 they are also apparent among less severely affected dry-mouth sufferers. The mastication of food can be uncomfortable or even painful; eating requires frequent sips of water, and swallowing is difficult. An analysis of xerostomia and OHRQoL among 32-year-old New Zealanders found that those with the condition were worse off in all aspects of OHRQoL.31 That the condition can have profound and disabling social consequences has been highlighted again recently, with a recent British report36 describing how sufferers of dry mouth reported considerable social impairment arising from their condition. Earlier work by Ship37 also highlighted the social effects of dry mouth. It is clear that dry mouth is not a trivial condition. Medications and dry mouth When the various risk factors for dry mouth are considered, medication is the one which most readily springs to mind. Older people take more medications than any other age group, and most nursing home © 2015 Australian Dental Association

Dry mouth and older people residents take even more medications than those living in their own homes. Particular medication types have been shown to be associated with dry mouth, but the entire relationship is not as straightforward as it might appear to be upon first consideration. All dentists have been taught at dental school that certain medications are associated with dry mouth, but exactly what medications are involved – and whether they are associated with SGH, xerostomia, or both – is less clear. The generic term ‘xerogenic’ was coined for use in referring to medications which are associated with dry mouth, because it covers both eventualities, whether xerostomia or SGH.38 Thus, xerogenic drugs have their effect either by reducing salivary flow or by altering the threshold for dry mouth perception so that xerostomia is experienced (or by doing both). There are many challenges in the area of medications and dry mouth, whether in conducting research or in understanding that which has already been published. It is fair to say that early work in the area was not noteworthy for its methodological rigour.8 Among the more recent studies, there have been differences in: the study design used; the population studied; the representativeness (or otherwise) of samples; how dry mouth is measured; how medication use is measured; and in the sophistication of the analyses. The issue of polypharmacy (the concurrent use of a number of different medications) among older people is a difficult one, with most studies avoiding it altogether. However, a small number of published studies have attempted to deal with it and these are considered further below. There is also the problem of whether a given drug’s apparent xerogenic effect is due to its effects or whether the dry mouth is a side effect of the underlying medical condition which is being treated. In a classic example, someone taking bronchodilators for emphysema may complain about dry mouth, but that dry mouth may be due to he/she having to breathe through the mouth (and the effort required to breathe) rather than the action of the bronchodilators. Alternatively (or even concurrently), it might be that sustained b-adrenergic stimulation by the bronchodilators being taken has resulted in viscous saliva which is of relatively low volume and wettability, leading to the symptoms of dry mouth. In such a situation, there is both a physical explanation and a pharmacological explanation, and it may be that a combination of these is operating.39 The literature on medications and dry mouth has so far not really acknowledged this issue. Interpreting the dry mouth literature is rather more complicated than it really needs to be because of differences in the way in which medication use has been measured.8 In brief, three general approaches have been used to study dry mouth and exposure to medications. First, researchers have looked for associations © 2015 Australian Dental Association

between dry mouth and the overall number of medications being taken, irrespective of the medication type or its xerogenicity.25,40 The findings of such studies support the prevailing view that medication is a risk factor for xerostomia, but they do not identify which medications are actually responsible. Thus, using the total number of medications is of little value. In the second approach, researchers have used lists of purportedly xerogenic medications41–43 to count the overall number of xerogenic drugs being taken by each participant. The problems with such classifications lie in their inclusivity, their variation, and their lack of specificity in respect of which aspect of dry mouth is caused. Again, the findings from studies using such lists tell us nothing about which medications are having the effect. In the third approach, associations have been examined by therapeutic category of medication (or even by individual preparation), with no preconceptions about xerogenicity. This is the most sensible way to do it, because it enables the issue of polypharmacy to be addressed, but it is also the most challenging in analytical terms. If someone taking an antidepressant has SGH, the first consideration is whether that side effect is actually due to other drugs which are being taken. A complication is that, other factors being equal, the more medications being taken, the greater the likelihood that an individual will be suffering from dry mouth, most likely because of his/her overall anticholinergic burden.13 This is illustrated in Fig. 1, which features simple cross-tabulations of xerostomia prevalence by the categorized number of medications being taken in two study samples from New Zealand and Australia.15,26 The gradient in xerostomia prevalence by the number of medications taken is apparent in adults irrespective of age. What those data do not tell us is which medications are responsible for the dry mouth. For that, we need to tackle the vexing issue of polypharmacy. How is that

Fig. 1 Prevalence of xerostomia (data are percentages) by number of medications taken, in population samples from New Zealand and Australia.15,26 59

WM Thomson done? The conventional, a priori hypothesis-testing approach would be to identify all of the medication combinations which are present in a sample and then to conduct analyses of the occurrence of dry mouth (as, for example, the mean salivary flow or mean XI score) against each of those. However, the risk of Type I error increases with the larger number of statistical tests which would be needed; for example, even if only the most prevalent 20 medication types are examined, there are still 219 (or 524 288) different possible combinations of medications to examine, and the Bonferroni-corrected alpha value for that number of tests would be ridiculously low, and beyond the output power of the usual statistical programmes. The analyses would also require meaningful numbers in each combination subgroup, such that the number involved in the study would need to be huge. These complications mean that analyses of medications and dry mouth should therefore have more of an exploratory approach than is usually the case. This is where exploratory data analysis comes into its own. Only three studies have attempted to deal with the polypharmacy issue. They all used exploratory data analysis to examine the effects of medications on aspects of dry mouth. Two of those were conducted on older people,5,15 and the other involved 32-year-olds26 and so will not be further considered here. In the first study,5 Johnson and colleagues examined the association between medications and stimulated parotid salivary flow rate in a sample of 154 patients in geriatric care. They used Automatic Interaction Detection (AID) analyses to do this, but were limited by both the low N and their decision to include socio-demographic and dental status variables in the AID analysis along-

side the medication variables. Nevertheless, they were able to identify that people taking a combination of antidepressants, antihistamines and diuretics had very low flow rates. A South Australian study conducted a few years later refined the approach, conducting the exploratory analyses with medications only15 (Fig. 2 and 3), and then using the identified medication combinations in multivariate models for dry mouth (separately for XI scores and unstimulated whole-saliva flow rate). Sociodemographic characteristics were included only at the multivariate modelling stage. The other methodological advance was that the medication exposure was characterized longitudinally, with measurements at baseline and then five years later. In multivariate models run subsequently using the AID-identified xerogenic medications, unstimulated flow rate was lower among individuals who were female or taking antidepressants at both baseline and five years, and higher among smokers or people who were taking statins. Dry mouth symptoms were more severe among females, as well as those taking: an anginal at baseline and five years; an anginal without a concomitant beta blocker at five years; thyroxine and a diuretic at five years; or antidepressants or antiasthma drugs at both baseline and at five years. Unstimulated flow rate was found to be lower among females or those taking antidepressants at both baseline and five years. It was higher among smokers and people taking one or more statins. Unfortunately, a subsequent examination of dry mouth and medications in the same cohort44 was not able to use exploratory data analysis because cohort attrition was so severe that the numbers remaining precluded it.

Fig. 2 Automatic Interaction Detection tree pattern for resting flow-rate using medication exposure at five years only (reproduced from Thomson et al. (2000) with the kind permission of Wiley Ltd). 60

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Dry mouth and older people

Fig. 3 Automatic Interaction Detection tree pattern for resting flow-rate using medication exposure from baseline to five years (reproduced from Thomson et al. (2000) with the kind permission of Wiley Ltd).

Managing dry mouth Managing dry mouth among older people involves making an appropriate diagnosis, relieving the symptoms, managing problems with dentures, preventing dental caries and soft-tissue involvement, and monitoring (and where necessary amending) the use of medications. Symptom relief is paramount, given what is known about the effects on quality of life.32,40 Symptomatic relief can be obtained simply and cheaply by using a small, inexpensive atomizer bottle filled with water; this can be readily kept on hand for symptomatic use by the sufferer. There are also a number of proprietary products on the market for relieving dry mouth. Sialogogues have shown mixed results, but they may be appropriate for some patients. Dry mouth can affect denture retention, and the absence of saliva can exacerbate a denture’s effects upon the mucosa in older wearers of complete dentures.45 Such patients may need denture adhesives to assist in prosthesis retention.37 Partial dentures add another complication; not only can there be retention problems, but the remaining natural teeth may be at greater risk. Loss of a key abutment tooth can be problematic. Preventing dental caries is a key concern, given current understanding that the disease continues unabated in older people46 and is even more active among older residents of nursing homes.47 Although © 2015 Australian Dental Association

the long-held assumption that older people taking xerogenic medications are at higher caries risk has been largely debunked,48 it is wise to be prudent and assume that an older person taking many medications is at even higher risk than he/she would be without those. Key measures are the twice-daily use of fluoride toothpaste and the avoidance of non-milk extrinsic sugars (such as sugar added to tea or coffee). Monitoring medication use is an important strategy. All health professionals treating older people should continually review and question medication regimens, particularly those which are longstanding. General medical practitioners should be encouraged to routinely ask older patients about dry mouth. Community pharmacists should also be encouraged to enquire routinely about dry mouth when consulted by older people. Enquiries about dry mouth could be included in the standard medical histories for older people admitted to hospital. Dentists need to work more closely with general practitioners and community pharmacists in order to raise awareness of dry mouth and to ensure that those suffering from it are able to be managed and advised in a timely and appropriate manner. CONCLUSIONS Common among older people, dry mouth is a condition which has important effects on sufferers’ 61

WM Thomson day-to-day lives. Appropriate and accurate measurement is critical for complete understanding of xerostomia and salivary gland hypofunction. Medications are the most important risk factor for dry mouth, and polypharmacy is common among older people. The management of dry mouth is challenging and needs to involve a multidisciplinary approach. DISCLOSURE The author has no conflicts of interest to declare. REFERENCES 1. Cassolato SF, Turnbull RS. Xerostomia: clinical aspects and treatment. Gerodontology 2003;20:64–77. 2. Hopcraft MS, Tan C. Xerostomia: an update for clinicians. Aust Dent J 2010;55:238–244. 3. Mandel ID. The diagnostic uses of saliva. J Oral Pathol Med 1990;19:119–125. 4. Locker D. Measuring oral health: a conceptual framework. Community Dent Health 1988;5:3–18. 5. Atchison K, Dolan TA. Development of the Geriatric Oral Health Assessment Index. J Dent Educ 1990;54:680–687. 6. Slade GD, Spencer AJ. Development and evaluation of the Oral Health Impact Profile. Community Dent Health 1994;11:3–11. 7. Osterberg T, Landahl S, Hedegard B. Salivary flow, saliva, pH and buffering capacity in 70-year-old men and women. J Oral Rehabil 1984;11:157–170. 8. Thomson WM. Issues in the epidemiological investigation of dry mouth. Gerodontology 2005;22:65–76. 9. Thomson WM, Chalmers JM, Spencer AJ, Ketabi M. The occurrence of xerostomia and salivary gland hypofunction in a population-based sample of older South Australians. Spec Care Dent 1999a;19:20–23. 10. Fox PC, Busch KA, Baum BJ. Subjective reports of xerostomia and objective measures of salivary gland performance. J Am Dent Assoc 1987;115:581–584. 11. Navazesh M. Methods for collecting saliva. Ann NY Acad Sci 1993;694:72–77. 12. Aps JK, Martens LC. Review: the physiology of saliva and transfer of drugs into saliva. Forensic Sci Int 2005;150:119– 131. 13. Chew ML, Mulsant BH, Pollock BG, et al. Anticholinergic activity of 107 medications commonly used by older adults. J Am Geriatr Soc 2008;56:1333–1341.

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© 2015 Australian Dental Association

Address for correspondence: Professor WM Thomson Sir John Walsh Research Institute The University of Otago PO Box 647 Dunedin 9054 New Zealand Email: [email protected]

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