Allostatic load and delirium in the hospitalized older adult

Delirium is a state of acute confusion and is common in hospitalized older adults. Risk factors for delirium have been described; however, less clearly defined are the pathophysiological mechanisms that lead to the development of delirium.

The purpose of this study was to investigate the relationship of allostatic load (AL), a cumulative measure of physiological dysregulation resulting from adaptation to acute and chronic stress, and delirium in the hospitalized older adult.

In this descriptive study, participants 65 years and older admitted to the hospital were included. Participants were excluded if they had severe cognitive dysfunction or had prevalent delirium. Ten parameters reflecting physiological activity across a range of regulatory systems were measured on admission. Separate scores were calculated for primary mediators and secondary outcomes, subsets of overall AL. Incident delirium was assessed 48 to 72 hours after admission.

Mean age was 75.7 years (range = 66 to 93 years). The incidence of delirium was 29%. The AL score derived from primary mediators, urinary cortisol, epinephrine and norepinephrine, and serum dehydroepiandrosterone sulfate predicted the incidence of delirium (odds ratio = 2.54, 95% confidence interval = 1.12-5.79, p < .05). The overall AL score, the score derived from secondary outcomes, and the individual AL measures were not related significantly to the incidence of delirium.

AL has been shown to be an important construct in the early identification of physiological dysfunction related to exposure to psychosocial and environmental stress. The findings from this study suggest that AL, particularly the primary mediators score, may be a useful measure in determining delirium risk in hospitalized older adults, leading to improved surveillance and prevention of delirium. A better understanding of AL may lead to interventions focused on reducing the impact of AL on the older adult's physiological function.