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Effects of Smartphone Use at Night with Light Emitting Diode Display With and Without Blue Light in Healthy Adults: A Randomized, Double-blind, Cross-over, Placebo-controlled Comparison
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| LED with bluelight | Sham Comparator | Two types of smartphone were used. One type had a conventional LED display with the full range of blue light. The LED in the other type newly developed by Samsung Display was suppressed for the blue light portion of the spectrum (wavelength 450 ~ 470 nm). The smartphones were indistinguishable from each other with the naked eye, because other wavelengths mimicked blue light in the suppressed LED. |
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| LED without bluelight | Experimental | Two types of smartphone were used. One type had a conventional LED display with the full range of blue light. The LED in the other type newly developed by Samsung Display was suppressed for the blue light portion of the spectrum (wavelength 450 ~ 470 nm). The smartphones were indistinguishable from each other with the naked eye, because other wavelengths mimicked blue light in the suppressed LED. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| smartphone display | Device |
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| Measure | Description | Time Frame |
|---|---|---|
| Changes of serum melatonin | serum melatonin levels were measured every 60 min from 7:00 PM on day 1 to 8:00 AM on day 2, from 7:00 PM on day 2 to 8:00 AM on day 3, and from 7:00 PM to 11:00 PM on day 3 for 3 days. | |
| Changes of serum cortisol | cortisol levels were measured every 120 min from 7:00 PM on day 1 to 8:00 AM on day 2, from 7:00 PM on day 2 to 8:00 AM on day 3, and from 7:00 PM to 11:00 PM on day 3 for 3 days. | |
| Changes of body temperature | body temperature was measured every 120 min from 7:00 PM on day 1 to 8:00 AM on day 2, from 7:00 PM on day 2 to 8:00 AM on day 3, and from 7:00 PM to 11:00 PM on day 3 for 3days. |
| Measure | Description | Time Frame |
|---|---|---|
| profile of mood states(POMS) | Mood was measured using the POMS,17 a well-validated self-report measure of mood states. | day 1,3 |
| Epworth Sleepiness Scale(ESS) | ESS18 is comprised of eight questions that query the subject's likelihood of dozing off or falling asleep in a particular situation that is commonly met in daily life. |
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Inclusion Criteria:
(1) Healthy males 20-40 years of age who understood the study procedure and agreed to participate after being fully informed about the study were included.
Exclusion Criteria:
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| day 1,3 |
| Fatigue severity scale(FSS) | The FSS20 is composed of 9 statements (items) that describe fatigue symptoms. Respondents select the most relevant level of agreement over the last week on a 7-point scale (1 strongly disagree; 7 strongly agree). | day 1,3 |
| continuous performance test(CPT) | Integrated visual-auditory CPTs were performed at days 1 and 3 by a psychologist who was an expert on cognitive tests | day1,3 |