Sleep and Cognitive Function in Shift Working Police Officers: Focusing on the Night Nap

Address for correspondence Sangha Lee, PhD Department of Psychology, Sungshin Women’s University, 2 Bomun-ro 34da-gil, Seongbuk-gu, Seoul 02844, Korea Tel: +82-2-920-7215 Fax: +82-2-920-2040 E-mail: xrpsychology@gmail.com Objectives: Currently, more than 80% of Korean police officers are assigned to a 24-hour rotating shift system. Shift workers’ sleep patterns change frequently, which may result in circadian rhythm desynchrony and sleep disturbance. The goal of this study was to compare sleep and cognitive functioning in different shift types. In addition, we analyzed the difference in cognitive functioning depending on whether shift workers took a night nap prior to their night shift. Methods: A total of 278 police officers working in Seoul (mean age 45.27±9.00 years, 88.5% male) participated, providing demographic information and completing selfreport questionnaires [Insomnia Severity Index, Epworth Sleepiness Scale, Munich ChronoType Questionnaire (Shift-work type), Patient Health Questionnaire-9]. Participants also performed the Psychomotor Vigilance Task, Trail Making Test A & B, and Stroop Test. Results: Participants included 57 (20.5%) day workers and 221 (79.5%) shift workers. The average Insomnia Severity Index score of shift workers was significantly higher than day workers (t=-2.861, p=0.005). Shift workers also slept about 0.78 hours less than day workers (t=4.730, p<0.001). Among shift workers, 66.3% (n=128) reported they took night naps prior to their night shift, sleeping on average 1.78 hours. Shift workers who took night naps had faster reaction times on the Trail Making Test A task [F(1, 136)=5.741, p=0.018], and significantly fewer Stroop C errors [F(1, 137)=5.638, p=0.019] than those who did not. Conclusions: Shift working police officers reported significantly worse insomnia symptoms and slept less compared to their non-shift-working counterparts. Taking a night nap improved focused and selective attention. J Sleep Med 2020;17(2):113-121