Effects of Smartphone Screen Colour Temperature on Sleep Quality: A Comparative Analysis of PSG, Smartwatch, and Sleep Questionnaire Methods

The use of smartphones at night could affect sleep cycles and even disrupting circadian rhythms. This study examines the effect of different smartphone screen colour temperatures on sleep quality, comparing low CCT (LC, 4000K), medium (MC, 5000K), and high (HC, 7300K) conditions. Sleep quality was measured using polysomnography (PSG), smartwatches, and sleep questionnaires. The results of three measurements consistently indicated that sleep quality was higher under the 5000K condition compared to 4000K, while the 7300K condition led to the poorest sleep quality. Notably, using a smartphone with a 7300K screen significantly reduced the proportion of REM sleep compared to reading printed books. Additionally, the study summarized the advantages of the three sleep assessment methods. PSG provided the most precise data, sleep questionnaires were easier to analyze, and smartwatches showed potential in detecting total sleep time but struggling with Rapid Eye Movement (REM) detection and sleep onset latency (SOL).