Smartphone ownership and screen time are increasing across the world, but there have been few attempts to quantify smartphone addiction on a global scale. We conducted a meta-analysis of studies published between 2014 and 2020 that used the Smartphone Addiction Scale, the most common measure of problematic smartphone use. We focused on adolescents and young adults (aged 15 to 35) since they tend to have the highest screen time and smartphone ownership rates. Across 24 countries, 83 samples, and 33,831 participants, we demonstrate that problematic smartphone use is increasing across the world. China, Saudi Arabia, and Malaysia had the highest scores while Germany and France had the lowest. We suggest that the clinical interpretation of these scores should be updated given current global trends.

No abstract

No abstract

Objective: Shift work causes circadian rhythms to misalign with the demands of the environment, which has been associated with sleep difficulties and cognitive impairments. Although bright light exposure during night shifts can improve circadian alignment, its implementation is often infeasible. Here, we tested whether light exposure in the evening, before the night shift, could improve fatigue, work performance, mood, and sleep. Methods: Fifty-seven healthy nurses who worked full-time rapidly rotating shift schedules completed the study. In a mixed-design randomised controlled trial, participants completed a baseline observation period before following one of two interventions. The experimental intervention aimed to improve circadian alignment using evening light exposure and morning light avoidance; the control intervention aimed to improve alertness and reduce sleep disturbances by modifying diet. Every morning and evening for 30 days, participants completed measures of fatigue, work-related errors, sleepiness, mood, sleep duration, and sleep quality. Results: Compared to the baseline observation period, the experimental intervention reduced errors by 67% while the control intervention reduced them by only 5%. This reduction was partially mediated by fatigue; experimental participants reported less fatigue on work days than control participants (d = 0.25 [0.12, 0.38]). The experimental group also showed a small improvement in mood. Both groups showed reductions in fatigue (d = .29 [.20, .35]) and sleepiness (d = 0.21 [0.13, 0.29]) as well as a small increase in sleep duration. Conclusion: Interventions based on evening light may thus be a feasible and effective strategy to reduce fatigue and errors in night shift workers.

Bright light exposure at night can help shift workers adapt to their schedules, but there has been relatively little research on evening light. We conducted a systematic review of studies that manipulated light exposure in the evening (broadly defined as 16:00 to 22:00) before real or simulated night shifts. Across the five eligible studies, evening light produced phase delays in melatonin, body temperature, and sleep propensity; increased sleep quality and duration; and improved memory and work performance. There were mixed effects for mood, no changes in sleepiness, and no negative effects. The confidence in these results ranged from moderate for physiological markers of circadian phase delays to very low for mood. Future studies should compare the relative effectiveness and safety of evening versus night-time light exposure. Overall, the benefits of evening light for shift workers are promising though tentative.