Delirium and the functional recovery of older medical inpatients after acute illness: the significance of biological factors

Abstract

Previous studies have not clarified the relationship of delirium to functional capacity during acute illness. We have investigated this relationship, incorporating the potential roles of APOE genotype and circulating cytokines in a longitudinal study of acutely admitted patients aged 70+ years. In all participants was measured the: Barthel Index (BI), mini-mental state examination (MMSE), confusion assessment method (CAM), delirium rating scale (DRS), APACHE II, APOE genotype. In a sub-sample: serum interferon-γ (IFN-γ), interleukin-1 (Levels of IL-1α, IL-1β and IL-1 receptor antagonist activity IL-1RA), interleukin-6 (IL-6), leukemia inhibitory factor (LIF), tumor necrosis factor-α (TNF-α) and insulin-like growth factor-I (IGF-I). Of 164 participants, mean age 84.6 ± 6.57 years (± S.D.), 67.1% were women. On first assessment, mean BI was 14.13 ± 4.46 and delirium prevalence was 25.6%. At discharge, the mean BI of survivors (n=150) was 15.61 ± 4.22. By discharge, survivors who had recovered from prevalent delirium had significant improvement in BI (n=38, p=0.005), but non-recovers did not (n=14, p=0.512). On, multivariate analysis, BI was significantly affected by MMSE, APOE, IL-1α, IL-6, LIF and TNF-α levels (p<0.05) but not by delirium. Delirium in acutely admitted patients is associated with functional decline only in those who do not recover. Biological factors, rather that delirium itself, may be responsible for this.