Xerostomia: a silent burden for people receiving palliative care – a qualitative descriptive study

Abstract

Background

The prevalence of dry mouth in the palliative care population is well documented and increases due to polypharmacy, radiotherapy and systemic conditions. Saliva as a lubricant for the mouth and throat has implications for swallowing, chewing, and speech. The literature about the experience of xerostomia (perceived feeling of dry mouth) in palliative care is scarce. Clinical evidence suggests that xerostomia has a negative impact on people’s comfort, however, no recent studies explored this impact in detail. This new knowledge is paramount to adhere to the principles of palliative care.

Aims

To evaluate the impact of xerostomia on the lives of people receiving palliative care with particular reference to eating and speaking. 

Design

A qualitative descriptive study (interview design). Thematic analysis was used for data analysis.

Setting

A single specialist palliative care centre in Ireland.

Results

The majority of participants (35/40) had cancer. Xerostomia was reported to have multiple physical, psychological, and daily life consequences. Participants provided insights into the impact of xerostomia on sleeping, eating, talking, denture wearing, and they described in detail their intra-oral sensations associated with xerostomia. The negative effect of xerostomia on speech was reported as the most significant to participants.

Conclusion

Xerostomia has a profound impact on the daily lives of people receiving palliative care, including physical and psychological consequences. Speaking is often affected, which can impede the person’s ability to communicate. There needs to be increased awareness of the impact of xerostomia and more research is required to understand how best to manage xerostomia in a palliative care setting.

Introduction

Historically, oral health has been described as a neglected area of health management [1]. More recent studies [2,3,4] exhort that due attention be paid to this important aspect of the body as it has been linked with increased mortality [5]. For all patients and especially patients receiving palliative care, oral health includes management of mucosa integrity, saliva levels, avoidance of pain, maintenance of teeth, and overall ensuring that patients in palliative care do not succumb to oral illness of any kind [6]. The issue of maintaining saliva levels and preventing dry mouth is particularly problematic in palliative populations [7]. In people receiving palliative care, the prevalence of dry mouth increases due to polypharmacy, radiotherapy, and systemic conditions [8,9,10,11].

Prevalence of dry mouth in palliative populations varies greatly depending on which measures are used but several studies rate perceived dryness at over 70% [3, 7, 12]. The National Institute for Health and Care Excellence (NICE) guidelines suggest a level as high as 88% in the terminally ill [13] and a more recent review article [14] reports that the level of xerostomia in end-of-life patients varied from 64 to 92%. In patients who are approaching death, dry mouth has been reported to be as high as 91% [15]. A further study rated it as the 3rd most prevalent symptom in a palliative population [16]. Yet, little is known as to why dry mouth receives so little attention as a symptom. The perceived sensation of dry mouth is called xerostomia [17, 18]. Xerostomia may be present even when there is no evidence of reduced salivary flow on oral examination [19]. Thus, the oral symptoms, as experienced by the patient, may differ significantly from visual observations. The issue of quality of saliva is also critical to the development of xerostomia [20].

Saliva is a complex substance [21]. Although saliva is comprised of over 99% water, in the remaining 1%, there are proteins and inorganic substances which make saliva different to plain water and which also give it crucial importance for oral comfort [22, 23]. The key functions of saliva such as protection, facilitation of food breakdown, bolus cohesion and transference through the gut, taste mediation, lubrication of mucosa, neutralisation of acid and oral pH maintenance are well documented [8, 22,23,24,25,26,27,28]. More recent articles suggest that the function of saliva extends far beyond what was previously thought regarding its antimicrobial properties [29]. The rapid healing of internal oral wounds when compared with external skin injuries has been attributed to saliva and its important enzymes such as histatins and leptin [29, 30].

It is recognised that the consequences of xerostomia for people receiving palliative care may be severe. Physical discomfort includes excessive thirst, unrelieved by water drinking [31]. Patients report interminable dryness extending from the lips to the throat [32] with fluctuations in levels which often worsens at night. This then can contribute to disrupted sleep patterns and increase in fatigue [33]. Other documented oral symptoms include poor mouth opening, candida, erythema, ulceration, stomatitis, mucositis, and dental decay [3, 12, 15, 26, 31, 34]. Denture fit can become a problem in cases of xerostomia and associated ulceration is a further reason for poor denture tolerance, which in turn can affect the quality of oral intake and chewing ability [35].

Apart from physical discomfort, xerostomia has been shown to result in several functional impacts which include difficulty speaking and eating [7, 32, 35,36,37]. Swallowing in cases of significant oral dryness can result in increased perceived swallow effort [38]. However, studies of palliative populations do not tend to refer to effort but note issues with mouth opening [34, 35], difficulty with chewing [35], higher levels of oral debris [34], or the need for softer foods or a change of diet [7, 32]. The issue of oral intake in the presence of xerostomia is further compounded by problems with the taste of food. A recent systematic review of taste and smell in palliative care patients found that the prevalence rate of taste and smell alterations varied between 60 and 86% [39]. However, methods of evaluating taste and swallow changes are often limited to self-reported ratings and no actual physical testing occurs in these studies. The actual nature of difficulties remains hidden as patients report that they self-manage eating issues through the use of increased amounts of water at mealtimes [7].

A second functional impact of xerostomia is difficulty with talking. Past studies of the effects of dry mouth suggest that the over-riding features observed include addition of a “click” while articulating; tiredness and struggle to speak is increased; changes in phonatory effort occur, as well as changes to voice range, vocal pressures and vocal stability [40,41,42]. Studies of the effects of xerostomia on the speech of patients receiving palliative care are few [7, 32, 35,36,37]. Findings refer to the high levels of effects on speech with difficulty talking being rated as the most important function affected in two most recent studies [7, 36]. However, studies do not detail the types of effect xerostomia has on speech or what exactly is happening as patients talk. Numerical rating scales are often used and older qualitative studies [32, 35] reflect on many themes without specific detailing of speech effects. Unlike previous research, this study provides personal accounts directly from patients about how their speech has been affected.

While the issue of xerostomia is well reported in certain systemic conditions such as Sjögren’s disease [19], renal dialysis [43], or diabetes [44], research in people receiving palliative care is scarce. A recent review on xerostomia in the population of people with advanced cancer concluded that the number of studies on this topic is still relatively small [45].

The majority of studies to date are completed by dentists and tend to be focused on the general area of oral care and they do not tend to address the issue of xerostomia specifically [15, 34, 36]. The identified prevalence of speech and swallowing issues [7, 27, 36] suggest that there is a need to investigate this area in more detail and particularly Speech and Language Therapists (SLTs) need to understand and manage these symptoms appropriately. Hearing the opinions of patients receiving palliative care and how xerostomia is affecting them is an important step in improving our understanding of this critical area of care.

According to the World Health Organisation (WHO) a key goal of palliative care is the relief of suffering through the early identification, correct assessment and management of any problems whether these are physical, psycho-social, or spiritual [46]. Increasing the comfort of patients receiving palliative care is paramount. Palliative care guidelines suggest that core values of palliative care include the need for comprehensive interdisciplinary assessment and to evaluate current practice so that new evidence is incorporated into protocols, policies, and procedures [47, 48]. This study aims to examine the impact of dry mouth for patients in palliative care, and to increase our understanding of how it is experienced by this group of patients. The hope is that this information may then contribute to changes in the way dry mouth is assessed and managed by the wider team and by SLTs.

Methods

A qualitative descriptive study [49, 50] was conducted to investigate the impact xerostomia has on the daily life of people receiving palliative care, particularly how does it influence their swallowing and speech. It was a part of a larger mixed-method study investigating the prevalence and severity of dry mouth in people receiving palliative care. Only the qualitative findings are included in this article. The method section is reported according to the Consolidated Criteria for Reporting Qualitative Research (COREQ).

Design

This qualitative descriptive study aimed to examine the experiences of xerostomia at a surface level [50], where the findings were interpreted and remained close to original data [51]. The study was underpinned by the naturalistic approach, which acknowledges the subjectivity/variability of participants’ experiences [48]. Similar qualitative descriptive designs have been used in the populations of cancer and palliative care [52, 53].

This research was initially planned before the Covid-19 pandemic. The design was subsequently modified prior to data collection in line with public health guidelines. Demographic data were collected through a chart review and qualitative data were collected via semi-structured interviews. A short interview guide was developed for this study (Appendix 1). All interviews were completed in person with safety measures in place and were time-limited to 15 min. This design was piloted on the first two participants. The research team met to discuss the pilot. Subsequently, no changes were made to the design and pilot data were included in the group analysis.

Participants and setting

Participants were recruited from a Specialist Palliative Care Service (SPCS) in Southern Ireland (in-patients and out-patients). The Australia-modified Karnofsky Performance Status scale (AKPS) is widely used as an indicator of phase of illness [54, 55]. On this scale, ranging from 10 to 100, the status of the patient is rated according to state of alertness, mobility (in bed/out of bed) and need for care. A level of 10 equates a patient who is barely rousable and patients above 70 are self-caring. For this study, only participants above 30 were eligible, as at this level patients are mostly bedfast and were deemed too unwell to participate. Thus, participants were not bedbound, continued to be communicative, but may have required significant care assistance.

As this research was part of a larger mixed methods study, where an examination of the mouth was also completed, a certain level of mouth opening was required, and this explains why patients with poor mouth opening (< 20 mm), or temporomandibular joint issues were excluded. Some potential participants were excluded on medical reasons. These included patients with medical contra-indications such as active Covid-19, severe respiratory distress, those using masks to support their breathing, medically unstable or those receiving active investigations/treatments which meant they were not available to participate even though xerostomia had been identified. Gatekeepers were medical and nursing staff who identified potential participants based on reports of xerostomia. Every potential participant was provided with a study invitation and information leaflet. Full list of eligibility criteria is in Table 1.

Table 1 Eligibility criteria

Data collection

Data were collected in 2019/2020 over a period of a year by the first author (EM), a Clinical Specialist Speech & Language Therapist experienced in specialist palliative care. Following written explanation about the study and informed consent, participants were interviewed (Appendix 1: Interview guide). All interviews were completed in a quiet room at a time suitable to the participant. Every effort to minimise interruptions was made. Interview times varied from early morning to late afternoon. Audio was recorded and investigator’s reflective diary was also maintained throughout the process. Medical files were consulted for demographic information (Table 2).

Data analysis

Raw data were imported to NVivo12 software [56]. In order to achieve familiarisation with the data and to begin the process of thematic analysis [57], the interviews were listened to and transcriptions completed. The transcripts were checked for accuracy against the original recordings, and corrections applied as necessary. Codes were applied to the raw data using the annotation system in NVivo12. A sample of data was independently coded by two authors (EM and DL) using an inductive approach, and EM then proceeded with coding. Codes were then reviewed, discussed by the research team, and themes were generated. A hierarchy of themes was established. The reflective diary also provided additional clarity and context when establishing themes.

Ethical issues

Ethical approval (ECM(00)14/01/2020) was received from the Clinical Research Ethics Committee Cork Teaching Hospitals and the Munster Technological University where EM was registered as a master’s student. The principles of justice, benevolence, non-malevolence, and autonomy [58, 59] guided the research procedures. The vulnerability of the population involved was considered at all times. Prior to being interviewed, the medical and emotional status of each participant was checked with the personnel in charge to ensure that no harm or undue stress would occur by participation. The interviewer also monitored for fatigue/discomfort during interviews and permitted a brief interruption of the interview where medications were necessary or due to be administered. All participants were carefully selected and were made aware both verbally, and in the participant information leaflet, that they could withdraw from the process at any stage. Procedures for informed consent and careful storage of all data adhered to the guidelines of the Ethics Committees and General Data Protection Regulations.

Results

52 participants were recruited for the study. 12 were excluded for the following reasons: condition deterioration (N = 7), early discharge home (N = 1), unsuitable visual or cognitive levels (N = 2), change of mind (N = 1) or xerostomia resolution (N = 1). Data were collected from a total of 40 participants (20 males and 20 females). 34 were in-patients, and 6 were out-patients (Table 2). The majority of participants were over 60 years (75%). Cancer was the most frequent diagnosis (87.5%) with gastro/colo/rectal comprising the largest group (30%). 24/40 participants had metastatic cancer. Only 5% of participants presented with progressive neurological conditions as their primary diagnosis. Multi-factorial co-morbidities, including heart, renal and respiratory conditions, were common among participants. Over 37% of participants were either independent or required only occasional assistance with self-care. The remainder, (62.5%), were in bed over half of the time or required frequent care.

Table 2 Participant demographics

Data analysis resulted in 10 codes [57], which were then grouped further into three main themes: (1) Physical effects of xerostomia, (2) Daily activity effects, and (3) Psychological effects (Table 3). Each theme will now be described.

Table 3 Table of themes

Theme 1. Physical effects of xerostomia

Having a sample of 40 participants resulted in a wide variety of terms being used to describe the overall physical sensation of xerostomia. While some participants could not find words to describe it apart from “just dry”, others provided more in-depth insights into precisely what was happening through the language of their descriptions. A sample of the responses provided include:

“It’s like superglue in your mouth” (P6).

“My tongue feels just like sandpaper” (P30).

Initial analysis of the above statements suggests that the over-riding sentiment is discomfort with negative connotations. However, when further analysed the statements give information about the possible differences in experiences for the participants. While for some the main symptom is dryness, for others the predominant physical sensation has more to do with “stickiness” and another sub-group refer to “coating” and “roughness”. Thus the perceived sensations experienced by all are not uniform.

In the sub-group of participants who referred to the predominantly sticky nature of saliva, the resulting physical manifestation was often serious and debilitating:

“It’s a nightmare, sometimes when I wake up my tongue is stuck to the roof of my mouth and you’ve got to peel it off and it’s very painful so I have to do it slowly………. I have to keep thinking “is my mouth frothy?” Because it goes all gooey, you know.” (P30).

Soreness, ulceration, tongue coating, or burning of the tongue were also listed as problematic tongue issues and while a few suggested that this might relate to thrush, many considered that friction or rubbing inside the mouth, which was more to do with dryness, was at the source of these painful intraoral sensations.

“It’s very unpleasant because my teeth are stuck to the inside of my mouth, it has created mouth ulcers on account of the friction.” (P26).

Many participants referred to specific locations of dryness. Some described it reached their throat and how it affected mouth opening:

“When I wake up in the morning my teeth would be clung to my mouth and my palate and you could hardly open the mouth you have to get some saliva from somewhere in your mouth to wet it but you can’t because it’s so dry.” (P9).

Others localised specific areas affected such as the lips, and a large cohort referenced issues with the tongue:

“This morning when I got up I felt the tongue had the cracks from the dry mouth.” (P12).

Theme 2. Daily activity effects of xerostomia

The following theme is categorised into a series of sub-themes which describe the effects of xerostomia on normal activities of daily living.

Effect on speech

Difficulty speaking (either at some point or on an ongoing basis) due to xerostomia was the richest and most frequent theme identified by the majority of participants (34/40). The predominant description related to difficulty forming words, slurring or mispronunciation of words. Participant 9 referred to the mouth as “seizing up” and Participant 30 also reported that the mouth was so stuck she could only mouth words. Descriptions such as “tongue tied” (P18), “stuttering” (P33), and “slushy” speech (P9) were also reported.

Participant 6, who reported severe xerostomia, also gives insight into the rapidity of how quickly xerostomia affected her when she was talking:

“It’s dry now and my lips are sticking to my lips as I’m speaking to you under the mask………… But, it’s down in my voice box and it’s very very dry and it seems to work its way up and then I could be talking and talking, I can’t talk no more now because I need something and it’s all starting to get dry now there and all the corners of my mouth go dry, my tongue. It’s like, it’s so, so dry….you could actually touch it, you get no saliva, no nothing off of it “. (P6)

Several referred to the need to have water nearby as a solution to allow them to speak more easily. However, for some people, the effects of taking the water were short-lived and it was only a very temporary solution:

“It’s just that people don’t find me distinct………No matter, as they say, what you drink ‘tis as bad as ever two seconds later again.” (P2).

When asked about why participants felt that their speech was affected, several reported a feeling that their lips were stuck to their teeth or denture and that this was the source of the issue in mispronouncing words:

“Yeah it’s just there the whole time, even while I’m talking to you now my lips are starting to stick to my teeth again.” (P38).

For others, the tongue was stuck “to the mouth”:

“It feels, have you ever heard the saying “stuck to the top of my mouth”, your tongue is stuck to the mouth and I find it hard to bring out words and talk.” (P17).

A few reported difficulty with mouth opening as being related to the speech issue:

“I’m like talking to you and I can feel my speech getting worse. It’s cos my mouth is getting drier. Then I haven’t had a sip in long time……. it’s words….unclear…I can’t keep my mouth open.” (P20).

Participant 6 reported that the difficulty extended to her throat and affected speech on all levels:

“It just hits you all of a sudden when you’re talking. If I’m talking for too long, my mouth goes dry and it actually goes dry from my tongue, my cheeks, my gums, all the way down to the back of my throat, down here in the voice box I can feel it.” (P6).

While others too referred to the effect on speech as a reduction in volume or talking more quietly sometimes associated with hoarseness:

“P: It makes it very quiet ……. And not clear”’ (P5).

Effect on eating, swallowing, and taste

Examination of the data relating to effects on eating or swallowing revealed that approximately half of the participants reported that xerostomia had little or no effect on their eating. Several referred to the fact that eating seemed to reduce the dry mouth effect. This stands to reason as the salivary glands are stimulated by chewing and the presence of food [30]:

“R: How is your eating at the moment do you think it’s been affected by the dry throat?

P: No problem. No, no because once you start eating it sort of nullifies the dry mouth in as much as what whatever you’re eating is helping you.” (P8).

Others suggested that eating was eased by the fact that they often used extra water when eating and this too reduced the issue of xerostomia:

“R: Has dry mouth affected your eating in any way?

P: No. It hasn’t really because I normally have water at the side of me when I’m eating anyway. (P29)

In those who did report issues with eating, the main problems related to difficulty with food sticking, oral soreness, chewing issues and difficulties with swallowing saliva when the mouth was dry. Some participants also complained of food sticking to the mouth, experiencing problems managing drier food consistencies, and difficulties swallowing tablets due to xerostomia:

“Sometimes when I swallow things get stuck, like the tablets, they won’t go because of the lumps, because it’s all dry and there’s nothing to wash them down. I usually have a drink first to wet my mouth and then take my medication, otherwise it won’t swallow. it sticks.” (P30).

Little/no influence of xerostomia on taste was reported by almost half of the sample. Participants who reported that their taste was affected (dysgeusia) attributed it to confounding factors such as chemotherapy, radiotherapy or cancer:

“I have no doubt that my taste has been affected, but there would be more to that than the dry mouth, I would think. As I said earlier, the medication would affect it also. I take a load of medication every day, and if I went to the leaflet about those medications, you’d find that this may lead to dry mouth or affect your sense of taste” (P14).

When participants reported that taste was affected by xerostomia, a wide variety of effects were reported. These included: food tasting bland, super-sensitivity of the taste buds, poor tolerance of salt in the mouth, and taste varying from meal to meal despite the same ingredients being used:

“everything in the mouth just tastes horrible…it doesn’t matter what it is….it could be cooked by Gordon Ramsey and I’d still find it’s just not…it’s horrible and then as I said ….next day, same thing cooked and it’s perfect” (P23).

Effects on other daily life activities

While speech and swallowing were a clear focus of this study, several other key daily activities were referred to as problematic because of xerostomia. Some participants specifically mentioned sleeping as being negatively affected by xerostomia:

“You’d be about to sleep but it won’t let you sleep. No, no, you would have to be sipping on the fluid all the time. I’d often wonder should I be on a drip at night”. (P15)

Kissing was also reported as influenced by xerostomia, as mentioned by Participant 1:

“And I can’t kiss even like this (demonstrates kiss on back of her hand).” (P1).

This participant demonstrated that even a “peck on the cheek” for her son was rendered difficult by xerostomia and it was clear that this was a daily frustration.

Issues with denture wearing were also reported but not consistently. Of the full or partial denture-wearers (16/40), only four participants made reference to xerostomia affecting denture wearing. A link between the length of wearing dentures and xerostomia was reported:

P: It gets a bit dry sometimes, especially if I leave my false teeth in too long so that the dentures are the main reason I get the dry mouth” (P11).

Theme 3. Psychological effects of xerostomia

A range of psychological effects of xerostomia was evident. For some, there was acceptance of the physical problem, and managing it so that it does not become psychologically challenging:

“It is quite dry but you get on with it.” (P25).

Frequently, this was directly linked with solutions that participants had found that soothed the physical elements which then prevented xerostomia from becoming a psychological issue:

“It’s no big deal really. I always carry a glass of water. I’m in a happy position where I do not need to let it bother me…. Because I can solve the problem by liquidising my mouth, by taking a sip of water. If I have the glass beside me all the time, it doesn’t bother me.” (P14).

For others it was evident that xerostomia affected them in more than just the physical sense of discomfort:

“P: It’s very very awkward and it affects your tongue and when you are moving your tongue I realise it, you don’t realise it if it isn’t doing that and when you are touching the roof of your mouth with your tongue a lot it’s getting dry all the time and when you stick out your tongue there’s a coating on it and that’s very annoying.” (P27).

The issue related often to the persistence of xerostomia and the fact that it was something additional that needed to be dealt with:

P: No, I haven’t learned to live with it. I would like to know that something out there is going to cure it. I would like that very much. Every day it is a nuisance. I can’t say tomorrow will be good because it’s not, it’s going to be the same. Dry mouth, goo, … stays the same.” (P30).

Some participants reported that xerostomia affected them profoundly. For example, Participant 15 rated xerostomia as high a burden as pain for the reason that it seemed never ending and that he had no cure for the dryness:

R: Describe to me how it feels to you .

P: All the time. No let up……. You’d be about to go to sleep but it won’t let you go to sleep. No, no, you would have to sipping on the fluid all the time……….

R: And in terms of all the symptoms you experience as a patient…. How does a dry mouth rate as a bother to you?

P: Number one anyway, is the lethargy. Not being able to walk from here to there without sitting down. Drained all the time. It is up there with two…. Pain, it’s not up there with pain, its next to pain. But why is it not up there with pain? Because I have pain control. (P15)

Some of the common emotions that were expressed by participants included: anguish, sadness, fear (particularly of suffocation), paranoia, embarrassment, fear of the judgement of others and finally mental exhaustion associated with the drudgery of dealing with xerostomia on a daily basis:

“It’s a big bother, it’s something I’m very paranoid about you know. First thing, my sister in law comes up every morning to see me and every morning it’s the same. I have to apologise because my mouth has started to froth up ……. She’s always like “don’t worry about it” but I do worry about it. It’s embarrassing and I have to keep thinking “is my mouth frothy?” (P30).

The aspect of fear associated with xerostomia was raised by several participants. For some, the issue of fear was far more serious, particularly when it referred to suffocation or choking:

“After I’d been home a few weeks, am, trying to take the tablets in the morning I says to my husband, this is horrible…my mouth is like sand. It ended up I was choking on the tablets which really frightened me…I felt that I couldn’t breathe. My mouth was getting worse. It was like tightness and I felt like I was being strangled and I was getting really panicky……. I couldn’t swallow so it was quite frightening……….You don’t think anybody will understand” (Tearful). ” (P20).

For others, the fear related to speaking and judgement by others and reference to curtailment of participation in socialising:

“Tis a funny thing that affects your speech, it affects your being…. You feel that you are afraid to make a speech or answer questions you know.” (P27).

Discussion

This study demonstrated that xerostomia is a significant and debilitating symptom for many people receiving palliative care. While water can relieve some of the temporary symptoms, the issue of the constancy of xerostomia is apparent and over time this tends to take a toll particularly when it affects speech, swallowing or results in oral soreness. This study confirms that the most common and reported as annoying consequences of xerostomia, include sticky saliva, roughness of tongue, a burning or soreness of tongue, and cracked lips. The personal accounts provided in this study indicate that while xerostomia may be an umbrella term for professionals, for those experiencing it, xerostomia has many different manifestations that may not have been reported until now.

This study indicates that xerostomia is a mainly silent burden which concurs with previous studies [60]. People receiving palliative care may not report xerostomia as they have so many other issues, such as pain, to deal with. However, when questioned it is obvious that xerostomia is having profound effects on their day-to-day lives. Although some accept it as an unpleasant inconvenience, for others it is a daily torture. While some studies [36] suggest xerostomia has a modest impact on the lives of people receiving palliative care, our study suggests that this impact is more significant, in line with other qualitative studies [32, 34] and it should not be a symptom which is overlooked. The persistent drudgery of dealing with xerostomia, evident in our participant reports, makes it clear that some were struggling psychologically with a type of “dry mouth fatigue”.

Xerostomia has multiple psycho-social consequences for people receiving palliative care [7, 32, 34], which was confirmed in our study. Loss and fear have already been reported [60] but for our participants the self-reports of how it can affect such everyday needs as sleep or kissing represents new information. Our study could be the first to report that xerostomia may have a profound influence on personal relationships, such as not being able to kiss or feeling unable to speak. There is a link between speech and how we are viewed by others especially when speech is perceived as impaired [61]. Participants referred to instances where they felt judged by others due to changes in either their voice or speech. The majority spoke of their sadness or embarrassment at not being able to produce their words immediately or to have them coming out inarticulately.

A few studies make reference to the effect of xerostomia on speech in the palliative population [7, 35, 40]. A study by Da Gama, et al., [40] where dry mouth was artificially induced, gives information about the processes happening during dry mouth speech. They found that phonemes remained unaffected and reported an additional “click” with extra speech tiredness and effort. Our participants did not refer to clicking but, instead, referred to slurring of speech, mispronounced words, difficulty forming words, etc. Thus, this seems to suggest problems with articulation and phoneme production which have not been identified in previous studies. Effects on voice quality were also mentioned by several participants in our study, This is in line with the findings of previous studies [41, 42] where dry mouth resulted in vocal instability, range changes and effort. Examination of the possible source of the difficulty with pronouncing words may be linked with participant reports of where they sourced their speech difficulty. While a few refer to their voice as the main issue, many refer to their lips being stuck together, or their lips being stuck to their teeth, or the tongue being stuck to either the teeth or palate. It is likely that lips stuck together or to the teeth will have effects on bilabial (e.g. /p/ or /b/) or labiodental sounds (/f/ or /v/), and any sticking of the tongue is likely to affect mainly alveolars (e.g. /t/, /d/ or /s/), and palatals (/ch/ or /j/) [62]. This would then result in slurred speech, but further research is necessary as several other factors such as airflow and timing must also be considered in the generation of normal speech [63]. Importantly, our study suggests that, until questioned, people with xerostomia receiving palliative care do not tend to mention their speech as an issue. At the very least SLTs need to be aware of the possibility that xerostomia can have an effect on speech in this population and should inquire about it. Assessment and management of xerostomia is necessary in the differential diagnosis of slurred speech and future research needs to examine this very prevalent finding.

In our study, for the majority of participants eating was not an issue, and may even ease the dry mouth sensation, due to the simple fact that they can use water to wash down food. As described by one participant, the act of eating “nullifies” the dry mouth sensation temporarily and it is known that eating stimulates increased saliva production [30]. With regard to chewing, while a few referred to difficulties obtaining bolus cohesion, a more frequently mentioned problem was the issue of friction which occurred during chewing. In cases where soreness co-occurred with dryness, the friction involved in chewing increased pain during eating and several reported changing to softer diets for this reason. This is problematic in itself as softer diets are likely to result in less stimulation of the periodontal membrane which helps to trigger increased saliva [30]. Management of the areas of soreness and friction are therefore primordial in such cases where this is reported. Finally, it is interesting that the issue of increased effort when swallowing with xerostomia, which has been recently reported in the literature [38], was rarely if at all mentioned by participants. This may, however, be more of a reflection of the persistent levels of fatigue experienced by most palliative patients who may not have been able to differentiate effort or fatigue associated with eating from the whole-body fatigue that they experience in doing any daily activity.

In conclusion, the impact of xerostomia in people receiving palliative care remains well hidden, perhaps overlooked, in the overwhelming plethora of other symptoms endured by this population. In the reduction of suffering, early identification of patient needs is a key principle of palliative care [46, 48, 64]. Xerostomia needs to be recognised as a potentially debilitating symptom and healthcare professionals need to be aware of the potentially profound impact of xerostomia on lives of people receiving palliative care.

Strengths and limitations

40 qualitative interviews generated a considerable wealth of qualitative data collected from people receiving palliative care, and this is therefore a strength of the study. Covid-19 related restrictions limited interview time and potentially disabled an in-depth exploration of experiences. However, given the characteristics of the population under study, longer or multiple interviews may not have been possible due to medical reasons. As this study was a part of a mixed method study involving an examination or oral mucosa, Sjögren’s syndrome was excluded from the population under study. Future qualitative studies could apply more comprehensive inclusion criteria and perhaps also consider the timing of onset of xerostomia as there may be important differences between xerostomia of short onset versus a more prolonged experience of this condition. Finally, polypharmacy is a known risk for xerostomia, and the researchers should investigate its impact on the personal experiences of people receiving palliative care.

Implications for policy, future practice, and research

Our study concluded that xerostomia is a symptom which can be persistent and problematic for many patients receiving palliative care and it requires careful assessment and questioning of the patient in order to determine the impact of xerostomia and the most appropriate management. While some may benefit from routine oral care and increased availability of water at the bedside, others are likely to require additional treatment such as the introduction of sialogogues. Further studies are also needed to determine more clearly ways to differentiate thirst from xerostomia. This may include the need for further discussion around dehydration effects and a more defined scale for evaluating thirst. A recent review of research priorities in palliative care concluded that more research capturing the voices of patients and families are required [65]. Several studies [2, 66] have shown that practices in the management of oral care vary enormously and future research needs to ensure that education turns into action [67]. The early provision of oral care and education regarding oral hygiene has been shown to be effective but is not widespread or systematic [12, 31]. While awaiting further research there is no cause for complacency and proactive education of the wider team, carers and patient, based on current best practice guidelines is advised. Finally, very frequent reports of speech effects of xerostomia are concerning and require further investigation so that appropriate management can be developed by SLTs.