The influence of chronic cigarette smoking on neurocognitive recovery after mild traumatic brain injury

The majority of the approximately 1.7 million civilians in the United States who seek emergency care for traumatic brain injury (TBI) are classified as mild (MTBI). Premorbid and comorbid conditions that commonly accompany MTBI may influence neurocognitive and functional recovery. This study assessed the influence of chronic smoking and hazardous alcohol consumption on neurocognitive recovery after MTBI. A comprehensive neurocognitive battery was administered to 25 non-smoking MTBI participants (nsMTBI), 19 smoking MTBI (sMTBI) 38 ± 22 days (assessment point 1: AP1) and 230 ± 36 (assessment point 2: AP2) days after injury. Twenty non-smoking light drinkers served as controls (CON). At AP1, nsMTBI and sMTBI were inferior to CON on measures of auditory-verbal learning and memory; nsMTBI performed more poorly than CON on processing speed and global neurocognition, and sMTBI performed worse than CON on working memory measures; nsMTBI were inferior to sMTBI on visuospatial memory. Over the AP1-AP2 interval, nsMTBI showed significantly greater improvement than sMTBI on measures of processing speed, visuospatial learning and memory, visuospatial skills, and global neurocognition, whereas sMTBI only showed significant improvement on executive skills. At AP2, sMTBI remained inferior to CON on auditory-verbal learning and auditory-verbal memory; there were no significant differences between nsMTBI and CON or among nsMTBI and sMTBI on any domain at AP2. Hazardous alcohol consumption was not significantly associated with change in any neurocognitive domain. For sMTBI, over the AP1-AP2 interval, greater lifetime duration of smoking and pack-years were related to significantly less improvement on multiple domains. Results suggest consideration of the effects of chronic cigarette smoking is necessary to understand the potential factors influencing neurocognitive recovery after MTBI.