Impact of smartphone use duration before bedtime on university students' sleep quality, total and concentration performances, and reaction time.

From a neurophysiological perspective, using a smartphone before bedtime may impact sleep quality and cognitive performance. This is because it can suppress melatonin production due to exposure to light. These effects can impact attention, information processing, and reaction time. This study aimed to investigate the impact of smartphone usage duration before bedtime on the sleep quality, total performance, concentration, and reaction time of university students. A total of 263 university students participated in the study. After applying inclusion and exclusion criteria, a final sample of 187 participants was selected for analysis. The PSQI questionnaire was used to assess the participants' sleep quality. Reaction time was evaluated through the ruler drop test. Total and concentration performances were measured using the U-cancellation software. Total performance (TP) is defined as the total number of items presented minus the number of errors (misses and false alarms). On average, students spend 75.78 min using their smartphones with the light on before bedtime, and 38.50 min with the light off. 70.1% (n = 131) of students reported poor sleep quality (score ≥ 5). The mean total and concentration performances were evaluated in the letter test (281.32 and 134.63) and picture test (281.49 and 135.63), respectively. 39.6% of students had reaction times categorized as below average or average. There was a significant positive correlation of moderate and weak strength between the duration of smartphone use before bedtime in both situations with the light on/off and sleep quality (r = 0.49, r = 0.33, p = 0.000) as well as reaction time (r = 0.47, r = 0.37, p = 0.000). Additionally, a significant inverse relationship was found between smartphone usage before bedtime and total performance (r = - 0.15, p = 0.037) and concentration (r = - 0.19, p = 0.009) letters. Students who use smartphones for over 1 h before bedtime with the light on, or for over 30 min with the light off, have 2.4 (CI:1.131-5.340; p = 0.023) to 3.7 (CI: 1.753-8.105; p = 0.001) times higher odds of experiencing poor sleep quality. In this sample, using smartphones for more than 60 min before bedtime, with the lights on, and for more than 30 min with the lights off, can be associated with higher odds of lower sleep quality. Furthermore, long-term smartphone use may be linked with prolonged reaction times, leading to slower responses among students. Additionally, smartphone usage may have a negative impact on their total performance and concentration. These thresholds should be interpreted with caution as they are derived from a specific sample and require further validation in larger and more diverse populations to confirm their generalizability.