Smartphone viewing distance and sleep: an experimental study utilizing motion capture technology

Abstract

There are studies reporting the negative impact of smartphone utilization on sleep. It is considered that reduction of melatonin secretion under the blue light exposure from smart-phone displays is one of the causes. The viewing distance may cause sleep disturbance, because the viewing distance determines the screen illuminance and/or asthenopia. However, to date, there has been no study closely investigating the impact of viewing distance on sleep; therefore, we sought to determine the relationship between smartphone viewing distance and subjective sleep status. Twenty-three nursing students (mean age ± standard deviation of 19.7±3.1 years) participated in the study. Subjective sleep status was assessed using the Pittsburgh Sleep Quality Index, morningness–eveningness questionnaire, and the Epworth sleepiness scale. We used the distance between the head and the hand while holding a smartphone to measure the viewing distance while using smartphones in sitting and lying positions. The distance was calculated using the three-dimensional coordinates obtained by a noncontact motion-sensing device. The viewing distance of smartphones in the sitting position ranged from 13.3 to 32.9 cm among participants. In the lying position, it ranged from 9.9 to 21.3cm. The viewing distance was longer in the sitting position than in the lying position (mean ± standard deviation: 20.3±4.7 vs 16.4±2.7, respectively, P<0.01). We found that the short viewing distance in the lying position had a positive correlation to a poorer sleep state (R2=0.27, P<0.05), lower sleep efficiency (R2=0.35, P<0.05), and longer sleep latency (R2=0.38, P<0.05). Moreover, smartphone viewing distances in lying position correlated negatively with subjective sleep status. Therefore, when recommending ideal smartphone use in lying position, one should take into account the viewing distances.

Associations between problematic Internet use and psychiatric symptoms among university students in Japan

“…In addition, based on recent studies on melatonin, the blue light emitted from a display such as a smartphone may play some role in sleep disturbance by altering melatonin . Moreover, we found that smartphones, when used in bed, are placed closer to subjects’ faces compared to other times of use, so any effects caused by the blue light may be stronger in that position …”

“…62 Moreover, we found that smartphones, when used in bed, are placed closer to subjects' faces compared to other times of use, so any effects caused by the blue light may be stronger in that position. 63 Furthermore, in research that examined Internet dependence over different years in the same region and with the same age group, the prevalence of PIU was found to be higher in newer surveys. 64 Increased accessibility to the Internet and commercial development of attractive devices and applications will likely continue to increase PIU scores in the future.…”

Decompensated esophoria and asthenopia correlated with electronic screens overuse in childhood: a case report

“…Yoshimura et al recently found that the viewing distance in the lying position was shorter than that in the sitting position, considering smartphones distances correlated negatively with subjective sleep status [16]. An American pilot study compared asthenopia using e-readers VS traditional paper format, constating a significantly higher rate of eyestrain (p = 0.008) and irritation (p = 0.011) in electronic devices group [17].…”

Difference in autonomic nervous effect of blue light depending on the angle of incidence on the eye

“…We therefore need to investigate and accumulate our knowledge to control the negative biological effects of blue light. Previous studies have suggested the influences of the distance to light source emitting blue light [14] and the angle of incidence on the eye. Studies reported that white light exposure to the inferior retina causes greater melatonin suppression than exposure to the superior retina [15,16].…”