Potential Risk Factors for, and Clinical Implications of, Delirium during Inpatient Rehabilitation: A Matched Case-Control Study

To investigate the association between a wide set of baseline characteristics (age, sex, rehabilitation discipline), functional scores [Functional Independence Measure (FIM), cumulative Illness Rating Scale (CIRS)], diseases, and administered drugs and incident delirium in rehabilitation inpatients and, furthermore, to assess clinical implications of developing delirium during rehabilitation. Matched case-control study based on electronic health record data. We studied rehabilitation stays of inpatients admitted between January 1, 2015, and December 31, 2018, to ZURZACH Care, Rehaklinik Bad Zurzach, an inpatient rehabilitation clinic in Switzerland. We conducted unconditional logistic regression analyses to estimate adjusted odds ratios (AORs) with 95% CIs of exposures that were recorded in ≥5 cases and controls. Among a total of 10,503 rehabilitation stays, we identified 125 validated cases. Older age, undergoing neurologic rehabilitation, a low FIM, and a high CIRS were associated with an increased risk of incident delirium. Being diagnosed with a bacterial infection (AOR 2.62, 95% CI 1.06-6.49), a disorder of fluid, electrolyte, or acid-base balance (AOR 2.76, 95% CI 1.19-6.38), Parkinson's disease (AOR 5.68, 95% CI 2.54-12.68), and administration of antipsychotic drugs (AOR 8.06, 95% CI 4.26-15.22), antiparkinson drugs (AOR 2.86, 95% CI 1.42-5.77), drugs for constipation (AOR 2.11, 95% CI 1.25-3.58), heparins (AOR 2.04, 95% CI 1.29-3.24), or antidepressant drugs (AOR 1.88, 95% CI 1.14-3.10) during rehabilitation, or an increased anticholinergic burden (ACB ≥ 3) (AOR 2.59, 95% CI 1.41-4.73) were also associated with an increased risk of incident delirium. We identified a set of factors associated with an increased risk of incident delirium during inpatient rehabilitation. Our findings contribute to detect patients at risk of delirium during inpatient rehabilitation.