Is there a link between alertness and fatigue in patients with traumatic brain injury?

Many patients with traumatic brain injury (TBI) report chronic fatigue, and previous studies showed a potential relationship between sleepiness and fatigue in these patients. Our study first looked at the impact of objective and subjective sleepiness on fatigue in patients with TBI. We then investigated how fatigue could affect driving performance in these patients.

Nocturnal polysomnography, the Fatigue Severity Scale (FSS), the Epworth Sleepiness Scale (ESS), and five 40-minute maintenance of wakefulness tests (MWT) were collected in 36 patients with TBI. Fitness to drive was assessed in a subsample of 22 patients compared to 22 matched controls during an hour simulated driving session.

In patients with TBI, FSS, ESS, and mean MWT scores (+/-SD) were 27 +/- 10, 8 +/- 4, and 35 +/- 7 minutes vs 15 +/- 2.5, 5 +/- 3, and 37 +/- 5 minutes in controls. Patients with TBI reported more chronic fatigue (W = 99, p < 0.001) than controls, and, unlike in controls, the level of chronic fatigue was correlated to their MWT scores. Patients' driving performances were worse than the controls' (W = 79, p < 0.001). The best predictive factors of driving performance were fatigue scores and body mass index (multiple R = 0.458, 41.8% of explained variance).

In patients with TBI, chronic fatigue is significantly related to subjective and objective levels of alertness, even though these levels are not highly pathologic. This might suggest that a small level of sleepiness (i.e., MWT scores between 33 and 39 minutes) worsens fatigue in these patients. Chronic fatigue and body mass index could predict driving simulator performance in patients with TBI.