Abstract: We included three trials with 3851 participants. All three were cluster-RCTs. Two of the trials were of complex, single-component, non-pharmacological interventions and one trial was a feasibility trial of a complex, multicomponent, non-pharmacological intervention. Risk of bias ratings were mixed across the three trials. Due to the heterogeneous nature of the interventions, we did not combine the results statistically, but produced a narrative summary. It was not possible to determine the effect of a hydration-based intervention on delirium incidence (RR 0.85, 95% confidence interval (CI) 0.18 to 4.00; 1 study, 98 participants; very low-certainty evidence downgraded for risk of bias and very serious imprecision). This study did not assess delirium prevalence, severity or mortality. The introduction of a computerised system to identify medications that may contribute to delirium risk and trigger a medication review was probably associated with a reduction in delirium incidence (12-month HR 0.42, CI 0.34 to 0.51; 1 study, 7311 participant-months; moderate-certainty evidence downgraded for risk of bias) but probably had little or no effect on mortality (HR 0.88, CI 0.66 to 1.17; 1 study, 9412 participant-months; moderate-certainty evidence downgraded for imprecision), hospital admissions (HR 0.89, CI 0.72 to 1.10; 1 study, 7599 participant-months; moderate-certainty evidence downgraded for imprecision) or falls (HR 1.03, CI 0.92 to 1.15; 1 study, 2275 participant-months; low-certainty evidence downgraded for imprecision and risk of bias). Delirium prevalence and severity were not assessed. In the enhanced educational intervention study, aimed at changing practice to address key delirium risk factors, it was not possible to determine the effect of the intervention on delirium incidence (RR 0.62, 95% CI 0.16 to 2.39; 1 study, 137 resident months; very low-certainty evidence downgraded for risk of bias and serious imprecision) or delirium prevalence (RR 0.57, 95% CI 0.15 to 2.19; 1 study, 160 participants; very low-certainty evidence downgraded for risk of bias and serious imprecision). There was probably little or no effect on mortality (RR 0.82, CI 0.50 to 1.34; 1 study, 215 participants; moderate-certainty evidence downgraded for imprecision). The intervention was probably associated with a reduction in hospital admissions (RR 0.67, CI 0.57 to 0.79; 1 study, 494 participants; moderate-certainty evidence downgraded due to indirectness). Our review identified limited evidence on interventions for preventing delirium in older people in LTC. A software-based intervention to identify medications that could contribute to delirium risk and trigger a pharmacist-led medication review, probably reduces incidence of delirium in older people in institutional LTC. This is based on one large RCT in the US and may not be practical in other countries or settings which do not have comparable information technology services available in care homes. In the educational intervention aimed at identifying risk factors for delirium and developing bespoke solutions within care homes, it was not possible to determine the effect of the intervention on delirium incidence, prevalence or mortality. This evidence is based on a small feasibility trial. Our review identified three ongoing trials of multicomponent delirium prevention interventions. We identified no trials of pharmacological agents. Future trials of multicomponent non-pharmacological delirium prevention interventions for older people in LTC are needed to help inform the provision of evidence-based care for this vulnerable group.

Plain-language summary: The evidence is current to February 2019. We found three studies that included 3851 participants. Two studies took place in the US and one study in the UK. One study tested whether delirium could be prevented by calculating how much fluid an older person in a care home needs each day and ensuring hydration was maintained. There were 98 people in the study, which lasted four weeks. One study tested the effect of a computer program which searched for prescriptions of medications that might increase the chance of developing delirium, to enable a pharmacist to adjust or stop them. There were 3538 people in the study, which lasted 12 months. One study tested an enhanced educational intervention which included learning sessions on delirium with care home staff and group meetings to identity targets for preventing delirium. There were 215 people in the study, which lasted 16 months. It was not possible to determine if the hydration intervention reduced the occurrence of delirium. This was a small study of short duration with serious design problems. The study of a computerised medication search programme probably reduced delirium, but there was no clear reduction in hospital admissions, deaths or falls. A potential problem is that it might not be possible to use this computer program in different countries that do not have similar computer systems available. It was not possible to determine if the enhanced education intervention reduced the occurrence of delirium and there was no clear reduction in the number of deaths. The intervention was probably associated with a reduction in hospital admissions. This is based on findings from a small study. There is very low-quality evidence on the effectiveness of hydration interventions for reducing the incidence of delirium. Therefore, it was not possible to draw firm conclusions. There is moderate-quality evidence that a computerised medication search programme may reduce the incidence of delirium. There is no clear evidence for reducing hospitalisations, mortality or falls. There is very low-quality evidence of the effectiveness of an enhanced educational intervention for reducing delirium. Therefore, it was not possible to draw firm conclusions. There is moderate-quality evidence for reducing hospital admissions. As this review only found a small number of research studies, we recommend that further research be conducted, testing different ways of preventing delirium for older people in LTC.