Understanding the association between pain and delirium in older hospital inpatients: systematic review and meta-analysis

Abstract

Objective: Delirium and pain are common in older adults admitted to hospital. The relationship between these is unclear, but clinically important. We aimed to systematically review the association between pain (at rest, movement, pain severity) and delirium in this population.

Methods: PubMed, EMBASE, CINAHL, PsycINFO, Cochrane and Web of Science were searched (January 1982-November 2022) for Medical Subject Heading terms and synonyms ('Pain', 'Analgesic', 'Delirium'). Study eligibility: (1) validated pain measure as exposure, (2) validated delirium tool as an outcome; participant eligibility: (1) medical or surgical (planned/unplanned) inpatients, (2) admission length ≥ 48 h and (3) median cohort age over 65 years. Study quality was assessed with the Newcastle Ottawa Scale. We collected/calculated odds ratios (ORs) for categorical data and standard mean differences (SMDs) for continuous data and conducted multi-level random-intercepts meta-regression models. This review was prospectively registered with PROSPERO [18/5/2020] (CRD42020181346).

Results: Thirty studies were selected: 14 reported categorical data; 16 reported continuous data. Delirium prevalence ranged from 2.2 to 55%. In the multi-level analysis, pain at rest (OR 2.14; 95% confidence interval [CI] 1.39-3.30), movement (OR 1.30; 95% CI 0.66-2.56), pain categorised as 'severe' (OR 3.42; 95% CI 2.09-5.59) and increased pain severity when measured continuously (SMD 0.33; 95% CI 0.08-0.59) were associated with an increased delirium risk. There was substantial heterogeneity in both categorical (I2 = 0%-77%) and continuous analyses (I2 = 85%).

Conclusion: An increase in pain was associated with a higher risk of developing delirium. Adequate pain management with appropriate analgesia may reduce incidence and severity of delirium.

Keywords: analgesia; delirium; general hospitals; older people; pain; systematic review.

Figure 1

Study selection PRISMA diagram.

Figure 2

Forest plot for subgroup meta-analysis, summarising ORs for the unadjusted association between pain and delirium risk (categorical pain data). Note: where studies are included more than once, data are derived from the same group of patients, but from multiple different time points; a higher OR value means a higher risk of delirium.

Figure 3

Forest plot for meta-analysis summarising SMDs between people with and without delirium (using continuous pain data). Note: where studies are included more than once, data are derived from the same group of patients, but from multiple different time points; a higher SMD value means a higher risk of delirium.