Lay summary – Some research studies have shown different results about whether deaths after traumatic brain injury (TBI) are increasing, decreasing, or staying the same. We still do not know enough about death rates among the most seriously ill TBI patients, especially those treated in intensive care units. It is also unclear how decisions to stop life-support treatment may have affected these trends. This study looked at TBI patients admitted to intensive care in England, Wales and Northern Ireland over the last 15 years. The aim was to understand how hospital death rates have changed over time, and how often life-support treatment was withdrawn.