System-Level Variability in Trauma Center Utilization for Seriously Injured Older Adults

Many seriously injured older adults are not transported to trauma centers (TCs), a phenomenon known as undertriage. System-level factors that contribute to undertriage are poorly understood. One important system-level factor is the regional supply of TCs. We hypothesized that regions with greater supply of TCs would have higher rates of transport to a TC for seriously injured older adults.

In this retrospective cross-sectional study using Medicare data from 2014 to 2015, we measured the proportion of seriously injured (injury severity score > 15) older adults (age ≥ 65 y) who were transported to a level I or level II TC within trauma service areas (TSAs), which consist of United States counties aggregated into contiguous geographic regions based on the most frequent hospital destinations for emergency conditions. Patients residing in rural regions were excluded. The primary outcome was transported to a level I or level II TC. The exposure was the supply of TCs within TSAs, grouped into terciles based on the number of TCs per capita. We performed a multivariable hierarchical logistic regression for the odds of TC transport with a random intercept for TSA and fixed effects for TC supply, patient demographics, and injury characteristics.

Our study included 68,128 seriously injured older adults residing in 309 TSAs. The tercile of TSAs with the lowest supply of TCs had 1.13 TCs per 1,000,000 population, and 38.8% of seriously injured older adults were transported to a TC. In contrast, the tercile with the highest supply of TCs had 4.15 TCs per 1,000,000 population, and 68.5% were transported to a TC. On multivariable hierarchical logistic regression, TSAs with the highest supply of TCs had four times higher odds of transport to a TC compared to TSAs with the lowest supply of TCs (odds ratio 4.23; 95% confidence interval: 3.32-5.38; P < 0.001).

Older adults with serious injuries are more likely to be transported to a TC in TSAs with greater supply of TCs. Ensuring an appropriate supply of TCs within TSA regions may help to reduce rates of undertriage for seriously injured older adults.