Impact of Blue Light Emitted by Smart Phones on Sleep Architecture and Chronotypes Among MBBS Students

CONTEXT: Smartphone usage has increased considerably over past two decades. Smartphone screens emit light rich in blue wavelength that has significant effects on neurophysiological functions. METHODS: 50 students from third MBBS were examined for sleep quality and sleep archetypes with Pittsburg Sleep Quality Inventory (PSQI) and Revised Morningness Eveningness Questionnaire (RMEQ). Their perceived smartphone usage was assessed with Smartphone Addiction Scale-Short Version (SAS-SV). Telemetric apps were used to measure their cumulative smartphone usage and lock-unlock cycles in a pre-determined 7-day period. Brightness of the smartphone screen was assessed with Lux-Meter-100k. RESULTS: We found 50% of the students suffering sleep problems as per PSQI cut off score. Students were non-significantly divided in terms of sleep archetypes. Mean cumulative smartphone usage was 2418±1052 minutes and mean lock-unlock cycle count was 483±216. Linear regression (F (2,47) = 8.625, P =0.001) showed that bed time (ß = -0.312, t = -2.497, P = 0.016) and smartphone usage post sunset (ß = 0.392, t = 3.134, P =0.003) to be the only significant predictors of PSQI score. Significant correlation was found between daytime dysfunction sub scale of the PSQI and cumulative smartphone usage (r=0.435, P<0.05) and total lock-unlock cycle count (r=0.394, P<0.05). CONCLUSIONS: Smartphone use affects sleep measures qualitatively and quantitatively. Continuous smartphone use as well as intermittent exposure affects certain measures of sleep quality. Telemetrical measurement of smartphone usage is an effective, simple and objective method for smartphone research.