Background: Delirium is a distressing, common and serious condition in older people in hospital. Evidence suggests that it could be prevented in about one-third of patients using multicomponent interventions _targeting delirium risk factors, but these interventions are not yet routinely available in the NHS.

Objective: The objective was to improve delirium prevention for older people admitted to the NHS.

Design: Project 1 comprised case studies employing qualitative methods (observation, interviews, workshops) in three NHS hospitals to develop the Prevention of Delirium system of care. Project 2 comprised case studies using mixed methods in five NHS hospitals to test the Prevention of Delirium implementation, feasibility and acceptability, and to modify the Prevention of Delirium system of care. Project 3 comprised a multicentre, cluster randomised, controlled, pragmatic feasibility study in eight hospitals, with embedded economic evaluation, to investigate the potential clinical effectiveness and cost-effectiveness of the Prevention of Delirium system of care, compared with standard care, among older patients admitted to hospital for emergency care. The primary objectives related to gathering information to design a definitive trial. Criteria for progression to a definitive trial were as follows: a minimum of six wards (75%) completing the Prevention of Delirium manual milestone checklist and an overall recruitment rate of at least 10% of the potential recruitment pool.

Setting: This study was set in NHS general hospitals.

Participants: In project 1, participants were staff, volunteers, and patient and carer representatives. In project 2, participants were staff, volunteers, patients and carers. In project 3, participants were older patients admitted to elderly care and orthopaedic trauma wards.

Intervention: The developed intervention (i.e. the Prevention of Delirium system of care).

Main outcome measures: For the feasibility study (project 3), the primary outcome measure was the Confusion Assessment Method. The secondary outcome measures were the Nottingham Extended Activities of Daily Living scale, the Clinical Anxiety Scale and the Geriatric Depression Scale Short Form.

Results: Project 1: understanding of delirium prevention was poor. Drawing on evidence, and working with ward teams, we developed the Prevention of Delirium system of care, which _targeted 10 delirium risk factors. This multicomponent intervention incorporated systems and mechanisms to introduce and embed delirium prevention into routine ward practices. Project 2: five out of six wards implemented or partially implemented the Prevention of Delirium intervention. A prominent role for hospital volunteers was intended, but most wards were unable to recruit or sustain the numbers needed. We identified four conditions necessary to implement and deliver the Prevention of Delirium intervention: (1) commitment of senior nurse, (2) a named person to drive implementation forward, (3) dedicated time (1 day per week) of an experienced nurse to lead implementation and (4) adequate ward staffing levels. Overall, the intervention was acceptable to staff, volunteers, patients and carers, and did not increase nursing staff workload. In the light of these findings, the Prevention of Delirium system of care was modified for use in project 3. Project 3: 16 wards in eight hospitals (two wards per hospital) were recruited. Out of 4449 patients screened, 3274 (73.6%) were eligible and 713 were registered, resulting in a recruitment rate of 16.0%. Thirty-three (4.6%) participants withdrew. The screened and registered participants were similar, but some between-treatment group imbalances were noted among those registered to the trial. All eight wards allocated to the intervention group completed the Prevention of Delirium manual milestone checklist and delivered the Prevention of Delirium intervention (median time 18.6 weeks for implementation). Overall, fidelity to the intervention was assessed as being high in two wards, medium in five wards and low in one ward. Of the expected 5645 Confusion Assessment Method delirium assessments, 5065 (89.7%) were completed during the first 10 days of admission. The rates of return of the patient-reported questionnaire booklets were 98.0% at baseline, 81.8% at 30 days and 70.5% at 3 months. The return rate of the EuroQol-5 Dimensions questionnaire was 98.6% at baseline, 77.5% at 1 month and 65.3% at 3 months (94–98% fully completed). The completion rate of the resource use questionnaire was lower (48.7%). The number of people with new-onset delirium at 10 days was 24 (7.0%) in the Prevention of Delirium group and 33 (8.9%) in the control group. Multilevel logistic regression analysis showed that participants in the Prevention of Delirium group had non-significant lower odds of developing delirium (odds ratio 0.68, 95% confidence interval 0.37 to 1.26; p = 0.2225). The average cost of the Prevention of Delirium intervention was estimated as £10.98 per patient and the mean costs for the Prevention of Delirium and usual-care groups were £5332 and £4412, respectively, with negligible between-group differences in quality-adjusted life-years. There was conflicting evidence from the trial- and model-based analyses relating to the cost-effectiveness of the Prevention of Delirium intervention. Given this, and in view of issues with the data (e.g. high levels of missingness), the results from the economic evaluation are highly uncertain. The criteria for continuation to a future definitive randomised controlled trial were met. Such a trial would need to recruit 5200 patients in 26 hospital clusters (200 patients per cluster).

Conclusions: The Prevention of Delirium system of care was successfully developed, and a multicentre feasibility study showed that the intervention is capable of implementation and delivery in routine care, with acceptable intervention fidelity and preliminary estimate of effectiveness.

Limitations: A prominent role for volunteers was originally intended in the Prevention of Delirium system of care, but only three of the eight wards allocated to the trial intervention group involved volunteers.

Future work: The findings indicate that a definitive multicentre evaluation of the Prevention of Delirium system of care should be designed and conducted to obtain robust estimates of clinical effectiveness and cost-effectiveness.

Trial registration: Current Controlled Trials ISRCTN28213290 (project 1), ISRCTN65924234 (project 2) and ISRCTN01187372 (project 3).

Funding: This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 9, No. 4. See the NIHR Journals Library website for further project information.