Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.

May combine two claims.

In humans, evening and early-night light exposure, even at low intensity, suppresses melatonin release and shifts the circadian clock later, making it harder to fall asleep at night.

“In humans, exposure to light in the evening and early part of the night, even at low intensity, suppresses the release of the sleep-facilitating hormone melatonin (3 -5) and shifts the circadian clock to a later time (3, 6), both of which make it more difficult to fall asleep at night.”

• cites [3] Zeitzer JM, Dijk DJ, Kronauer R, Brown E, Czeisler C (2000) Sensitivity of the human circadian pacemaker to nocturnal light: Melatonin phase resetting and suppression. J Physiol 526(Pt 3):695 -702. sourceSupported
• cites [4] McIntyre IM, Norman TR, Burrows GD, Armstrong SM (1989) Human melatonin suppression by light is intensity dependent. J Pineal Res 6(2):149 -156. sourceNot checked — no full text of the source
• cites [5] Brainard GC, et al. (1988) Dose-response relationship between light irradiance and the suppression of plasma melatonin in human volunteers. Brain Res 454(1-2):212 -218. sourceNot checked — no full text of the source
• cites [6] Khalsa SBS, Jewett ME, Cajochen C, Czeisler CA (2003) A phase response curve to single bright light pulses in human subjects. J Physiol 549(Pt 3):945 -952. sourcePartly supported

  The Abstract and Results (pages not provided) report that bright-light exposure caused phase delays when timed before the core body temperature minimum; the Discussion also suggests small phase-shifting effects of dim light. The paper does not establish that low-intensity evening light suppresses melatonin release or makes it harder to fall asleep. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Lux is an inappropriate measure for estimating light's impact on melatonin suppression, circadian-phase shifting, and other non-image-forming retinal effects.

“For this reason, it has recently been proposed that lux is an inappropriate measure for estimation of the impact of light on melatonin suppression, circadian-phase shifting, and other non -imageforming effects of retinal light exposure (35).”

• cites [35] Lucas RJ, et al. (2014) Measuring and using light in the melanopsin age. Trends Neurosci 37(1):1 -9. sourceSupported

May combine two claims.

Using light-emitting devices just before bedtime is a concern because light is the strongest environmental signal affecting the human circadian clock and may help perpetuate insufficient sleep.

“The use of light-emitting devices immediately before bedtime is a concern because light is the most potent environmental signal that impacts the human circadian clock and may therefore play a role in perpetuating sleep deficiency (1).”

• cites [1] Czeisler CA (2013) Perspective: Casting light on sleep deficiency. Nature 497(7450): S13. sourceSupported

Classified as probably not a substantial claim.

The circadian-timing system synchronizes many internal physiological and biochemical processes, including the daily rhythm of sleep propensity, to external environmental time cues.

“The circadian-timing system synchronizes numerous internal physiological and biochemical processes, including the daily rhythm of sleep propensity (2), to external environmental time cues.”

• cites [2] Dijk DJ, Czeisler CA (1995) Contribution of the circadian pacemaker and the sleep homeostat to sleep propensity, sleep structure, electroencephalographic slow waves, and sleep spindle activity in humans. J Neurosci 15(5 Pt 1):3526 -3538. sourceSupported

May combine two claims.

Recent evidence links chronic melatonin suppression by nocturnal light exposure to increased risk of breast, colorectal, and advanced prostate cancer associated with night-shift work, which WHO has classified as a probable carcinogen.

“The results of this study are of particular concern, given recent evidence linking chronic suppression of melatonin secretion by nocturnal light exposure with the increased risk of breast, colorectal, and advanced prostate cancer associated with night-shift work (for review, see ref. 10), which has now been classified as a probable carcinogen by the World Health Organization (11, 12).”

• cites [10] Costa G, Haus E, Stevens R (2010) Shift work and cancer - considerations on rationale, mechanisms, and epidemiology. Scand J Work Environ Health 36(2):163 -179. sourcePartly supported

  The “Shift work and cancer” section reports moderately increased breast-cancer risk after prolonged shift work, more limited observations for colorectal and prostate cancers, and IARC’s classification of shift work involving circadian disruption as probably carcinogenic (page unavailable). “Concluding remarks” links light-at-night melatonin suppression to breast cancer and possibly prostate cancer, but the copy does not establish that mechanism for colorectal cancer or specify advanced prostate cancer. The WHO-classification clause has separate citations in the citing sentence. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [11] Straif K, et al. (2007) Carcinogenicity of shift-work, painting, and fire-fighting. Lancet Oncol 8(12):1065 -1066. sourceNot checked — no full text of the source
• cites [12] Erren TC (2010) Shift work, cancer and ' white-box ' epidemiology: Association and causation. Epidemiol Perspect Innov 7:11. sourcePartly supported

  The Discussion (pages not provided) describes nocturnal light as suppressing melatonin and reports increased breast-cancer risk in shift workers and findings compatible with increased prostate-cancer risk. It does not report a colorectal-cancer association or distinguish advanced prostate cancer, and it cautions that the observed risks may not reflect a real association with chronodisruption. The probable-carcinogen classification is attributed to other references in the citing sentence. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The Karolinska Sleepiness Scale is a 9-point Likert scale with valid point values, where odd numbers have descriptions from 1 (extremely alert) to 9 (extremely sleepy).

“The KSS is a 9-point Likert scale with all numbers having valid point values, but only the odd numbers have descriptions: 1 representing ' extremely alert, ' 3 representing ' alert, ' 5 representing ' neither alert nor sleepy, ' and 9 representing ' extremely sleepy ' (9, 41).”

• cites [9] Åkerstedt T, Gillberg M (1990) Subjective and objective sleepiness in the active individual. Int J Neurosci 52(1 -2):29 -37. sourceNot checked — no full text of the source
• cites [41] Gillberg M, Kecklund G, Åkerstedt T (1994) Relations between performance and subjective ratings of sleepiness during a night awake. Sleep 17(3):236 -241. sourcePartly supported

  The Methods (p. 2) describe the KSS as a nine-point scale from 1 (“very alert”) to 9 (“very sleepy, fighting sleep, an effort to keep awake”), with verbal descriptions at every second point. Our copy does not give the descriptions for points 3 and 5, so those specific labels in the citing sentence are not verified. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Other studies have not found a relationship between alertness and melatonin levels during light exposure, or have shown light-induced alertness changes during the day when melatonin is low or undetectable.

“Other studies, however, have not found a relationship between alertness and melatonin levels during light exposure (20, 21) or have shown changes in alertness induced by light exposure during the day, when melatonin levels are at low or undetectable levels (22 -24).”

• cites [20] Dollins AB, Lynch HJ, Wurtman RJ, Deng MH, Lieberman HR (1993) Effects of illumination on human nocturnal serum melatonin levels and performance. Physiol Behav 53(1):153 -160. sourceNot checked — no full text of the source
• cites [21] Chang AM, Scheer FA, Czeisler CA, Aeschbach D (2013) Direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans depend on prior light history. Sleep 36(8):1239 -1246. sourceNot checked — no full text of the source
• cites [22] Phipps-Nelson J, Redman JR, Dijk DJ, Rajaratnam SM (2003) Daytime exposure to bright light, as compared to dim light, decreases sleepiness and improves psychomotor vigilance performance. Sleep 26(6):695 -700. sourceNot checked — no full text of the source
• cites [23] Rüger M, Gordijn MC, Beersma DG, de Vries B, Daan S (2006) Time-of-day-dependent effects of bright light exposure on human psychophysiology: Comparison of daytime and nighttime exposure. AmJPhysiol Regul Integr Comp Physiol 290(5):R1413 -R1420. sourceSupported
• cites [24] Vandewalle G, et al. (2006) Daytime light exposure dynamically enhances brain responses. Curr Biol 16(16):1616 -1621. sourceNot checked — no full text of the source

May combine two claims.

The LE-eBook condition suppressed evening melatonin by 55.12 ± 20.12%, while the print-book condition showed no suppression (-18.77 ± 39.57%) on the fifth night (P < 0.001).

“The LE-e-book condition suppressed evening levels of melatonin by 55.12 ± 20.12%, whereas the print-book condition showed no suppression ( -18.77 ± 39.57%) as measured during the fifth night ( P &lt; 0.001; Fig. 2 A and B ).”

May combine two claims.

Reading the LE-eBook was associated with decreased evening sleepiness; an hour before bedtime, participants rated themselves less sleepy (P < 0.01) and had less EEG delta/theta power (1.0-7.5 Hz) in the LE-eBook condition.

“Reading the LE-eBook was associated with decreased sleepiness in the evening. An hour before bedtime, study participants rated themselves as less sleepy ( P &lt; 0.01; Fig. 3 D ), and their EEG showed less power within the delta/theta frequency range (1.0 -7.5 Hz; Fig. 3 D and E ) in the LE-eBook condition.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Measurements from several other light-emitting devices are also enriched for short-wavelength light.

“As shown in Table S1, measurements from several other lightemitting devices are also enriched for short-wavelength light.”

May combine two claims.

There was no difference between the LE-eBook and print-book conditions in total sleep time, sleep efficiency, or duration of non-REM sleep (stages 1-3).

“There was no difference between conditions in TST, sleep efficiency, or the duration of non-REM sleep (stages 1 -3; Fig. 3 C ) in the sleep episode, which were scheduled for eight hours each.”

May combine two claims.

Light from the LE-eBook is short-wavelength-enriched, peaking at 452 nm in the blue range, compared with broad-spectrum white light peaking at 612 nm.

“Light from the LE-eBook is short-wavelength -enriched, with a peak at 452 nm in the blue light range, compared with broad-spectrum light (white light), with a peak at 612 nm.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Twelve young healthy adults (six women, six men; mean age 24.92 ± 2.87 years) completed the 14-day in-patient protocol.

“Twelve young healthy adults completed the 14-d in-patient study protocol (six females and six males; mean age ± SD: 24.92 ± 2.87).”

May combine two claims.

The LE-eBook's peak irradiance is about 450 nm, while the reflected light from the printed book peaks at 612 nm.

“The peak irradiance for the LE-eBook eReader is ∼ 450 nm and for the reflected light is 612 nm.”

The quote only partly states this claim.

Under dim room light, the LE-eBook at maximum brightness produced much higher photopic and melanopic illuminance than the printed book.

“LE-eBook | 31.73 | 31.64 | 31.03 | 31.68 | 31.84 | 30.69”

• Also stated in: § Materials and Methods · p. 5 · plain

  “Print book* | 0.91 | 0.45 | 0.65 | 0.68 | 0.81 | 0.92”

May combine two claims.

The decreased evening sleepiness and longer sleep latency in the LE-eBook condition are likely due to both an acute alerting effect of light and a circadian timing delay.

“The decreased sleepiness before bedtime and longer sleep latency we observed in the LE-eBook condition is likely due to both an acute alerting effect of light and a delay of the circadian timing system.”

May combine two claims.

The study did not include a longer-wavelength light-emitting device for comparison, so the findings may be due to differences in irradiance rather than spectral composition.

“Lastly, although the short-wavelength light from the LEeBook may have been responsible for the effects reported here, this study did not include a light-emitting device with longer wavelength for comparison, so our findings may be due to the difference in irradiance level rather than spectral composition.”

May combine two claims.

The change in REM sleep timing likely represents a delay in the circadian rhythm of REM sleep propensity, which coincides temporally with the sleep propensity rhythm.

“The change in the timing of REM sleep likely represents a delay in the circadian rhythm of REM sleep propensity, which is temporally coincident with the sleep propensity rhythm (25).”

• cites [25] Czeisler CA, Zimmerman JC, Ronda JM, Moore-Ede MC, Weitzman ED (1980) Timing of REM sleep is coupled to the circadian rhythm of body temperature in man. Sleep 2(3):329 -346. sourceNot checked — no full text of the source

May combine two claims.

The difference in morning sleepiness between conditions is most likely due to differences in the prior sleep episode and/or the circadian-phase delay.

“Therefore, the difference in morning sleepiness between the conditions is most likely due to differences in the prior sleep episode and/or the circadian-phase delay.”

Classified as probably not a substantial claim. May combine two claims.

All participants completed both reading conditions but were randomized to the order.

“All participants completed both reading conditions but were randomized to the order.”

May combine two claims. The quote only partly states this claim.

Melatonin suppression was assessed on the fifth and final evening of each condition; using the shifted AUC from the following evening should control for any phase shift, so the greater suppression was not due to a delayed phase in the LE-eBook condition.

“Therefore, the greater suppression seen was not due to an effect of a delayed phase in the LE-eBook condition.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The LE-eBook reader was held at a fixed distance (30-45 cm) from the eye, which is farther than many people might choose, reducing retinal light exposure, especially for users of smaller devices held closer.

“Moreover, in this study, the LE-eBook reader was held at a fixed distance (30 -45 cm) from the eye, further from the eye than many people might have chosen (therefore reducing retinal light exposure), particularly for users of smaller devices who may hold the smaller screens closer to the eyes.”

Classified as probably not a substantial claim.

Participants' abstinence from medications, drugs, alcohol, nicotine, and caffeine for three weeks before admission was confirmed by toxicological testing.

“Participants were instructed to refrain from use of medications, drugs, alcohol, nicotine, or caffeinated products for 3 wk before admission, which was verified by toxicological testing upon admission to the laboratory.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The Karolinska Drowsiness Test provided standardized and reproducible conditions for waking EEG recording with minimized movement artifacts.

“The KDT allowed for waking EEG recording under standardized and reproducible conditions where artifacts from movement were minimized.”

• cites [9] Åkerstedt T, Gillberg M (1990) Subjective and objective sleepiness in the active individual. Int J Neurosci 52(1 -2):29 -37. sourceNot checked — no full text of the source

Classified as probably not a substantial claim.

Sleep and circadian measures were compared between reading conditions using a mixed model with condition, order, and condition×order as factors.

“We compared sleep and circadian measures between reading conditions using a mixed model analysis with factors Condition (LE-eBook or printed book), Order , and their Interaction ( Condition X Order ).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Participants were randomized to the order of the reading conditions.

“Participants were randomized to the order of reading condition.”

Probably not a substantial claim: may not pass S3 (load-bearing).

KSS scores and EEG power were compared using a mixed model with condition, order, time, and condition×time as factors.

“Mixed model was also used for comparing KSS score and EEG power with factors Condition , Order , Time (repeated measures in the first hour after awakening), and the Interaction ( Condition X Time ).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

A technician was present at all reading sessions to ensure compliance and to collect light measurements.

“A technician was present for all reading sessions to coordinate and administer the reading session, ensure compliance of the participants, and collect and record the light measurements.”

Classified as probably not a substantial claim. The quote only partly states this claim.

Participants maintained a fixed 8-hour sleep schedule (10 PM to 6 AM) for three weeks before admission, verified by wrist actigraphy.

“Participants were also required to maintain a fixed 8-h sleep schedule (10:00 PM to 6:00 AM), to complete a daily sleep/wake log, and to call in their bedtimes and wake times every day during this 3-wk interval. This sleep schedule was verified by wrist actigraphy (Actiwatch-L; Philips/Respironics) during the week before admission.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The melatonin radioimmunoassay used had a functional sensitivity of 0.9 pg/mL, analytical sensitivity of 0.3 pg/mL, intraassay precision of 7.9-8.2%, and interassay precision of 11.7%.

“Plasma melatonin samples were assayed (SolidPhase Inc., Portland, ME) using the BÜHLMANN Melatonin Radio-immunoassay (ALPCO Diagnostics, Salem, NH), which has a functional sensitivity of 0.9 pg/mL and an analytical sensitivity of 0.3 pg/mL, an intraassay precision of 7.9 -8.2%, and interassay precision of 11.7%.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Melatonin suppression and phase were each determined in 11 participants because one participant was excluded from each analysis due to missing blood samples.

“Because of missing blood samples during the fifth night of one reading session, one study participant was excluded from analysis of melatonin suppression. Another participant was excluded from analysis of DLMO timing due to missing blood samples during one of the CPs. Therefore, melatonin suppression and phase were each determined in 11 participants.”

Classified as probably not a substantial claim. May combine two claims.

The study used a randomized crossover design with two conditions: reading an LE-eBook versus reading a printed book.

“The randomized, crossover protocol design consisted of two conditions: ( i ) reading an LE-eBook (iPad; Apple Inc., Cupertino, CA) in otherwise very dim room light for ∼ 4 h before bedtime for five consecutive evenings, and ( ii ) reading printed books in the same very dim room light for ∼ 4 h before bedtime for five consecutive evenings (Fig. 1).”