Three methods for examining trajectories in neuropsychological performance across the first 4 years after mild Traumatic Brain Injury

Emerging data suggest that recovery from mild traumatic brain injury (mTBI) takes longer than previously thought. This paper examines trajectories for cognitive recovery up to 48 months post-mTBI, presenting these visually using a Sankey diagram and growth curve analysis.This sample (n = 301) represents adults (≥16 years) from a population-based Brain Injury Outcomes in the New Zealand Community study over a 4-year follow-up on the CNS-Vital Signs neuropsychological test. Data were collected within 2 weeks of injury, and then at 1, 6, 12 and 48 months post-injury.Significant improvement in cognitive functioning was seen up to 6 months post-injury. Using growth curve modelling, we found significant improvements in overall neurocognition from baseline to 6 months, on average participants improved one point per month (0.9; 95% CI 0.42–1.39) p < 0.001. No change in neurocognition was found within the time periods 6–12 months or 12–48 months. The Sankey highlighted that at each time point, a small proportion of participants remained unchanged or declined. Proportionally, few show any improvement after the first 6 months.Most individuals remained stable or improved over time to 6 months post-injury. Summary statistics are informative regarding overall trends, but can mask differing trajectories for recovery. The Sankey diagram indicates that not all improve, as well as the potential impact of individuals moving in and out of the study. The Sankey diagram also indicated the level of functioning of those most likely to withdraw, allowing targeting of retention strategies.