Weekend effect in emergency hospitalizations of older adults in Hong Kong

The impact of the weekend effect on hospitalization outcomes remains debated. This study evaluated the "weekend effect" by defining two distinct patterns based on admission-discharge timing: "weekend-admission/discharge" (either admission or discharge occurring on weekends) and "weekday-admission-discharge" (both admission and discharge occurring on weekdays). Utilizing 3,447,877 emergency hospitalization spells among older patients in Hong Kong from 2012 to 2021, multivariable logistic regression with a random effect of hospital revealed that the weekend-admission/discharge pattern accounted for 42.5% of hospitalizations and was associated with significantly higher in-hospital mortality (5.0% vs. 3.8%; adjusted odds ratio [aOR] = 1.359, 95% CI: 1.344-1.373). Paradoxically, this pattern demonstrated minimally protective effects for post-discharge outcomes, with lower 30-day mortality (aOR = 0.963, 95% CI: 0.948-0.978) and reduced 30-day emergency readmission risk (aOR = 0.986, 95% CI: 0.979-0.992). Subgroup analyses confirmed consistent elevation of in-hospital mortality risk across all spell groups, while revealing substantial variations by length of stay, clinical specialty, and principal diagnosis. The protective post-discharge effects were predominantly observed among those with longer hospitalizations. These findings demonstrate a complex duality in weekend care outcomes and suggest that the weekend effect reflects systemic care integration challenges and selective discharge patterns rather than simple temporal variations in care quality. Future quality improvement initiatives should focus on enhancing care continuity and developing targeted approaches for high-risk clinical contexts. Meanwhile, more research is needed to elucidate the underlying mechanisms driving these paradoxical outcomes.