Does using a smartphone before bedtime affect sleep patterns?

April 1, 2019

The NHRI investigation shows smartphone use before bedtime delays circadian rhythm and reduces sleep times. The 2017 Nobel Prize in Physiology or Medicine Winning Theme “Controlling the molecular mechanisms for circadian rhythm”, pointed out that irregular sleep patterns may increase the risk of psychiatric and medical illnesses. For academia and clinicians, there is difficulty in long-term (months or years) naturalistic and objective recording of daily sleep patterns. The NHRI Team led by Dr. Yu-Hsuan Lin, has developed a smartphone-based automatic sleep recording system – “Rhythm” which successfully solves this barrier to research. By using this system, Dr. Lin’s team have precisely estimated that smartphone use before bedtime affects circadian rhythm and sleep time.

Dr. Lin’s research discovered, that one hour of smartphone use during the day delays circadian rhythm by 3.5 minutes and decreases total sleep time by 5.5 minutes. Smartphone use before bedtime was only around 14.3% of total use, but had around 44% of the impact on sleep. Previous literature shows light exposure significantly impacts circadian rhythm. Dr. Lin’s research team demonstrated that use before bedtime significantly affects circadian rhythm. The research results have recently been published in the March 2019 issue of the Journal of Psychiatric Research.

The research team comprises researchers from National Health Research Institutes (NHRI), National Taiwan University Hospital, Mackay Memorial Hospital, Chiao Tung University, and Dan Jiang University, with expertise in the fields of psychiatry, psychology, statistics, electrical engineering and computer science. The investigation utilized the “Rhythm” app and continuously collected smartphone use data for 14 days along with a questionnaire. A significant amount of data was collected and analyzed for use patterns and sleep times.

The method in which the “Rhythm” App collects sleep and use data is based on the times of the screen turning on and off. Most importantly, Dr. Lin’s team is the first one to propose “proactive use” (turning on the smartphone, making phone calls, using applications) and “reactive use” (receiving calls, receiving notifications) in their analytical algorithm to predict sleep times and to precisely calculate the impact of smartphone use on sleep times. Statistical analysis shows our methodology has 84% correlation to results from the user questionnaire.

Dr. Lin notes that most apps currently on the market must be manually set and the users have to wear or place the devices bedside in order to monitor and record behavior. Once the user forgets to set, wear, or properly place the device, the data collection will be interrupted. The “Rhythm” App is completely automatic and collects data continuously and calculates sleep times from this data. The App is also power efficient.

Dr. Lin also notes that the “Rhythm App” can continuously and automatically record use patterns and sleep times over long periods, and therefore can be utilized for sleep and health monitoring. In addition, the “Rhythm” App can precisely calculate smartphone use and its impact on sleep, and the collected data from the App is more objective then a user’s self-report or questionnaire. The “Rhythm” App is considered to be a breakthrough in research methodology, and will have great application potential in the fields of sleep medicine and psychiatry.

For the full text of our publication in the Journal of Psychiatric Research, please visit:

Media contact:

Dr. Yu-Hsuan Lin, Institute of Population Health Sciences, National Health Research Institutes, TEL: +886-37-246-166 ext.36383, E-mail:   

Nathalie Huang, Secretariat, National Health Research Institutes, TEL: +886-37-246-166 ext.32113, E-mail:

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