The Adverse Effects and Events of Thickened Liquid Use in Adults: A Systematic Review

Practice pattern studies suggest that liquid modification is currently a primary strategy used by speech-language pathologists to manage dysphagia; however, the breadth of negative consequences associated with their use is not well understood. The purpose of this review was to summarize the evidence on adverse events and effects of thickened liquid (TL) use in adults.

Six databases were searched in February 2022: EMBASE, MEDLINE (PubMed), Speechbite, AMED, AgeLine, and CINAHL. Articles were included if they compared adults receiving different TL viscosities and discussed at least one adverse event or effect of consuming TLs. Articles were excluded if they were review articles, rehabilitation studies, rheological analyses, not in English, or not peer reviewed. Screening and data extraction were completed by two independent reviewers. Risk of bias was assessed using Cochrane tools.

Thirty-three studies (N = 4,990 participants across all studies) were eligible for inclusion (2,405 unique records screened). Reported adverse events included dehydration (n = 5), pneumonia (n = 4), death (n = 2), urinary tract infection (n = 1), and hospitalization (n = 1); adverse effects included reduced quality of life (n = 18), aspiration (n = 12), reduced intake (n = 8), increased residue (n = 4), and reduced medication bioavailability (n = 2). Results were mapped on to codes and domains of the International Classification of Functioning, Disability and Health.

A range of adverse outcomes associated with TL use were identified. Adverse outcomes should be monitored and reported in dysphagia research. Given current research evidence, it is vital for clinicians to weigh the risks and benefits of TL use to mitigate potential adverse outcomes.