0698 PER3 POLYMORPHISM PREDICTS DIFFERENTIAL COGNITIVE IMPACTS OF CIRCADIAN MISALIGNMENT IN SHIFT WORKERS

Abstract

Introduction: Some night-shift workers are more impacted by circadian misalignment than others, resulting in differential impairments to cognitive performance. One explanation may be a polymorphism in the period 3 gene, as 4- and 5-repeat alleles have been shown to predict differences in cognitive performance and alertness after sleep loss. However, the role of Per3 polymorphism in shift workers has not been examined, and may have implications for circadian interventions. This study examined if Per3 genotypes differed in the cognitive consequences of circadian misalignment in night-shift workers. Methods: Thirty fixed night-shift workers (22 female) were enrolled in a large observational study examining the health and performance consequences of circadian misalignment. Participants were genotyped as having the 5-repeat allele (Per35/-; n=20) or not (Per34/4; n=10). Circadian phase was assessed hourly via salivary melatonin for 24 hours (dim light melatonin onset). Nocturnal sleepiness was assessed using Multiple Sleep Latency Tests (every two hours from 11pm to 5am). Cognitive flexibility was measured using a computerized task-switching paradigm (tested at 5:30am), which indexed switch-cost (efficiency in switching to a new task) and set-inhibition (efficiency in suppressing previous task rules). Results: As expected, individuals with a delayed circadian phase exhibited less sleepiness (r = -.50, p < .01), though this relationship did not differ by Per3 genotypes. Individuals with delayed circadian phase also showed greater cognitive flexibility (r = .40, p .05). Conclusion: Results suggest that Per35/- shift workers may experience cognitive deficits resulting from factors beyond circadian misalignment. As prior studies have demonstrated increased susceptibility to sleep disruption in Per35/- individuals, future studies may explore the role of variable sleep timing in cognitive performance, particularly because night shift workers commonly switch to nighttime sleep on nights-off.