Background
Individuals with dementia often present with swallowing difficulties (dysphagia). The consequences can include choking, dehydration, malnutrition, weight loss, pneumonia and death. Modification of food and liquid is a popular management strategy. It is believed that increasing the viscosity of liquids or altering the consistency of food allows individuals a better opportunity to swallow, with a reduced risk of choking or liquids entering the airway. However, there is growing evidence suggesting that this strategy can lead to dehydration, malnutrition, negative psychological/social consequences, and can affect quality of life for the person with dementia.
Review question
We wished to find out if changing the viscosity or consistency of food or fluids, or both, makes swallowing safer and has positive outcomes for people with dementia in terms of respiratory status, nutritional status and quality of life. We wanted to examine if modifying food or fluids, or both, also had any adverse effects for the person with dementia.
Study characteristics
We found two studies, which were both part of the same multicentre trial and included people with dementia and people with or without dementia and Parkinson's disease. We included data on people with dementia only. The first of the two studies looked at the immediate effects of two viscosities of liquids compared to regular thin liquids on aspiration (entry of food or fluid into the lungs) in 351 people with dementia. This study also compared drinking regular thin liquids using a chin down head posture as well as drinking regular thin liquids without any changes to head position; the main outcome was fluid entering the lungs. Using a subgroup of 260 people with dementia from the first study, the second study compared the effect of the same liquid viscosities with a chin down head posture. The effectiveness of these interventions on the incidence of pneumonia and adverse effects of these interventions was examined over a three-month period.
Study results
Honey thick viscosity liquids, which clinically are similar to descriptions of 'very thick liquids', had a more positive immediate impact on preventing fluid entering the lungs when examined during videofluoroscopy (specialised swallow x-ray) examination. However, during the three-month follow-up period there were a greater number of incidents of pneumonia in the group of people with dementia receiving these honey thick liquids, than those receiving nectar thick liquids and those receiving regular thin liquids with a chin down posture. There were no deaths classified as 'definitely related' to the type of liquids that the person with dementia was receiving.
Conclusion
There were a number of methodological flaws in both studies in this review and these were acknowledged by the authors. While thickening fluids may have an immediate positive effect on swallow function, clinicians should consider the effects of this intervention on the person with dementia in the longer-term. People with dementia on thickened fluids require long-term follow-up. The overall risk of bias of included studies is high. The quality of evidence is low. Further well-designed research is needed.
We are uncertain about the immediate and long-term effects of modifying the consistency of fluid for swallowing difficulties in dementia as too few studies have been completed. There may be differences in outcomes depending on the grade of thickness of fluids and the sequence of interventions trialled in videofluoroscopy for people with dementia. Clinicians should be aware that while thickening fluids may have an immediate positive effect on swallowing, the long-term impact of thickened fluids on the health of the person with dementia should be considered. Further high-quality clinical trials are required.
People with dementia can have feeding and swallowing difficulties (dysphagia). Modification of the consistency of food or fluids, or both, is a common management strategy. However, diet modification can affect quality of life and may lead to dehydration and malnutrition. Evidence on the benefits and risks of modifying food and fluids is mandatory to improve the care of people with dementia and dysphagia.
To determine the effectiveness and adverse effects associated with modifying the consistency of food and fluids in improving oral intake and eliminating aspiration in adults with dysphagia and dementia.
We searched ALOIS (the Specialised Register of the Cochrane Dementia and Cognitive Improvement Group), the Cochrane Library, MEDLINE via Ovid SP, Embase via Ovid SP, PsycINFO via Ovid SP, CINAHL via EBSCOhost, LILACS via BIREME, ClinicalTrials.gov and the World Health Organization (WHO) Portal on 9 May 2018. We also checked the reference lists of relevant articles to identify any additional studies.
We included randomised controlled trials (RCTs), quasi-RCTs and cluster-RCTs published in any language that measured any of the outcomes of interest. We included trials with adults with a clinical diagnosis of dementia with symptoms and signs of dysphagia confirmed on instrumental assessment. We included participants with all types, stages and severities of dementia. Control groups received either no intervention or interventions not involving diet modification or modification to sensory properties of food.
Two review authors independently assessed for inclusion all potential studies identified. Data were extracted independently along with assessment of methodological quality using standard Cochrane methods. We contacted study authors for additional unpublished information.
No trials on modification of food met the inclusion criteria. We included two studies that examined modification to fluids. Both were part of the same large multicentre trial and included people with dementia and people with or without dementia and Parkinson's disease. Participation in the second trial was determined by results from the first trial. With unpublished data supplied by study authors, we examined data from participants with dementia only. The first study, a cross-over trial, investigated the immediate effects on aspiration of two viscosities of liquids (nectar thick and honey thick) compared to regular liquids in 351 participants with dementia using videofluoroscopy. Regular liquids with a chin down head posture, as well as regular liquids without any intervention were also compared. The sequence of interventions during videofluoroscopy may have influenced response to intervention. The second study, a parallel designed RCT, compared the effect of nectar and honey thick liquids with a chin down head posture over a three-month period in a subgroup of 260 participants with dementia. Outcomes were pneumonia and adverse intervention effects. Honey thick liquids, which are more consistent with descriptors for 'spoon thick' or 'extremely thick' liquids, showed a more positive impact on immediate elimination of aspiration during videofluoroscopy, but this consistency showed more adverse effects in the second follow-up study. During the second three-month follow-up trial, there were a greater number of incidents of pneumonia in participants receiving honey thick liquids than those receiving nectar thick liquids or taking regular liquids with a chin down posture. There were no deaths classified as 'definitely related' to the type of fluids prescribed. Neither trial addressed quality of life. Risk of bias for both studies is high. The overall quality of evidence for outcomes in this review is low.