Background. First responders have a higher risk of developing dementia before the age of 65. The Los Angeles fires of January 2025 was one of the largest fires in U.S. history, requiring deployment of over 4,700 firefighters. We aimed to assess the baseline cognitive function of active-duty Los Angeles Fire Department (LAFD) firefighters.

Methods. We enrolled active-duty LAFD firefighters to undergo cognitive testing with the Montreal Cognitive Assessments (MoCA), with total scores categorized as normal (≥26), mildly abnormal (23-25), and moderately abnormal (<23). We analyzed data overall and by age.

Results. Of the 235 firefighters (mean age 42; 96% male), 79 (33%) had mildly impaired cognitive performance (MoCA 18-25), with 65 (28%) of firefighters having mildly abnormal and 14 (6%) having at least moderately abnormal MoCA scores. Of the 61 firefighters aged >50, 11.5% had moderately abnormal MoCA scores.  A substantial proportion of abnormal scores were attributable to the delayed recall (75.3%) and sentence repetition (43.4%) subdomains. Linear regression analyses revealed a significant association of MoCA scores with self-reported pre-encounter hours of sleep (P<0.001) among participants age <40 years but not in participants aged 40 years or older.

Conclusion. A standardized neurocognitive assessment revealed a relatively high prevalence of abnormal scores in active-duty Los Angeles firefighters, especially in those age 50 or older. The extent to which cognitive testing results reflect transient situational as opposed to early neurodegenerative changes requires further investigation