Study of Heart Rate and Blood Pressure Subject to Pulsed LED Lighting

ABSTRACT It has been proved that lighting has nonvisual effects on the human body, including changes in heart rate and blood pressure. Heart rate and blood pressure are associated with the autonomic nervous system and can indicate stress level. The present study investigates whether heart rate and blood pressure are influenced by the frequency or duty cycle of pulsed light, together with the duration of lighting. Twelve healthy young subjects were recruited for the investigation. Subjects were exposed to pulsed light of varying frequencies (40 Hz, 100 Hz, 300 Hz) and duty cycles (10%, 50%, 90%). Exposure time was divided into two groups: short-time (20 min) and long-time (3 hours). Heart rate and blood pressure were measured during the experiments. Results showed that after a short lighting period (20 min), heart rate and blood pressure were significantly higher under 40 Hz pulsed than that under stable light, while 100 Hz and 300 Hz had no significant difference. After 3 hours of exposure time, the two indices became higher under 100 Hz (no flicker perceived with eyes) with 10% duty cycle, while 50% and 90% duty cycle showed no significant difference. These findings indicate that pulsed light will cause a deviation of heart rate and blood pressure from that under stable light.