Background: 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.

Objectives: 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.

Search methods: 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.

Selection criteria: 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.

Data collection and analysis: 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 We contacted study authors for additional unpublished information.

Main results: 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 With unpublished data supplied by study authors, we examined data from participants with dementia only.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.

Authors' conclusions: 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.

Eadaoin Flynn ‐ none known Christina H Smith ‐ none known Cathal D Walsh ‐ none known Margaret Walshe ‐ none known