Association between low income and ICU delirium among critically ill older patients: A retrospective cohort study in Japan

Abstract

Background

The social determinants of delirium have yet to be well-studied. We explored the association between low-income and intensive care unit (ICU) delirium among critically ill older patients in Japan, where universal healthcare coverage is provided.

Methods

This was a retrospective cohort study. Study patients included 2705 adults aged 70 years or older who were admitted to the ICU of St. Luke's International Hospital in Tokyo for a mean duration of 4.3 (SD = 6.0) days between March 2014 and April 2022. Patients classified in the low-income categories of the public health insurance system or receiving public assistance were designated as the low-income group. ICU delirium was assessed using the Confusion Assessment Method-ICU. The Cox proportional hazards model was used to estimate the associations between low income and delirium.

Results

508 patients (18.8%) were categorized as low-income. Delirium occurred in 1055 patients (39.0%) during ICU stay. After adjustment for age, sex, hearing or vision impairment, alcohol abuse, psychiatric disorders, cognitive impairment, cerebrovascular disease, and physical function, low-income showed a 1.20 times greater risk of ICU delirium (95%CI: 1.04−1.39, p = 0.014). After adjustment for potential mediators in addition to the confounding factors, low-income remained at 1.17 times greater risk of ICU delirium (95%CI: 1.01−1.36, p = 0.035).

Conclusions

In a Japanese ICU, low income was found to be an independent risk factor for ICU delirium. Future studies are needed to elucidate the mechanism of the association between low income and delirium in Japanese critically ill older patients.