n = 13 M = 13 mean age 23.8 ± 5.0 years | ~75 lx | 5 h (7:30 p.m.–12:30 a.m.) | 1. LED screen—6953 K 2. No LED screen—4775 K | <8 lx | Laboratory | MEL in saliva | SIGN effects for screen, time of day, interaction screen vs. time of day | (Bues et al. 2012) [121] |
n = 12 M = 6, F = 6 mean age 24.92 ± 2.87 years | Printed book 0.91 lx LED ebook 31.73 lx | 4 h before bed time every day (6:00–10:00 p.m.) 5 days each session | N/A | ~3 lx ambient room light level | Laboratory | MEL in plasma | LED ebook: −55.12 ± 20.12% * Printed book: 18.77 ± 39.57% NS between sessions * | (Chang et al. 2015) [139] |
n = 16 M = 16 (20–28 years) | 40 lx | 2 h (9:30–11:30 p.m.) | Fluorescent lamps: 6500 K 2500 K incandescent lamp: 3000 K | 0 lx | Laboratory | MEL in saliva | 6500 K: * MEL increase to pre-light exposure levels: 6500 K: 29.5 ± 5% 3000 K: 49 ± 7.6% 2500 K: 42 ± 8.6% | (Chellappa et al. 2011) [122] |
n = 9 M = 6; F = 3 mean age 25.7 ± 3.0 years | LED tablet: 38.4 ± 23.2 lx (min–max: 1.5–148.2 lx) | 2× 5 consecutive evenings (6:00–8:45 p.m.) | N/A | Printed book: 0.7 ± 0.2 lx (min–max: 0.2–1.4 lx) | Laboratory | MEL in plasma | LED tablet: 54.17 ± 18%; printed: 9.75 ± 22.75%; LED tablet delayed bedtime for 30 min, MEL secretion for ~1 h and sleep onset for 30 min | (Chinoy, Duffy, and Czeisler 2018) [140] |
n = 67 M = 38; F = 29; pre- to mid-pubertal group (9.1–14.7 years); late- to post-pubertal group (11.5–15.9 years) | 15 lx 150 lx 500 lx | 4 consecutive nights 1 h evening group (11:00 p.m.–12:00 a.m.) morning group (3:00–4:00 a.m.) | N/A | 0.1 lx | Laboratory | MEL in saliva | Evening light exposure: pre- to mid-pubertal group MEL SUP: 15 lx: −9.2 ± 20.5% 150 lx: −26 ± 17.7% 500 lx: −36.9 ± 11.4% late- to post-pubertal group MEL SUP 15 lx: −5.3 ± 17.7% 150 lx: −12.5 ± 17.3% 500 lx: −23.9 ± 21.7% Evening light exposure between age groups: SIG Morning light exposure between age groups: NS | (Crowley et al. 2015) [135] |
n = 4 M = 4 (20–21 years) | 1. 18 lx (29 μW/cm2) for blue LED 2. 450 lx (170 μW/cm2) for mercury vapor | 1 h (1:00–2:00 a.m. and 5:00–6:00 a.m.) | Blue LED, mercury vapor lamp | Dimly illuminated area | Laboratory | MEL in plasma | 1: −34 ± 9% * 2: −18 ± 6% *
| (Figueiro, et al. 2004) [123] |
n = 40 M = 22 (18–54 years, median = 21 years) F = 18 (18–35 years, median = 23 years) | 1. 30 lx 2. 100 lx 3. 300 lx 4. 1000 lx (at the cornea) | 40 min, 2 experimental sessions (2:00–2:40 a.m., 3:40–4:20 a.m.) | 4100 K 8000 K | Dim light (red LED) | Laboratory | MEL in plasma | SIGN effect of light level and spectrum 4100 K: 1: 3 ± 11% 2: 10 ± 4% 3: 38 ± 7% 4: 38 ± 6% 8000 K: 1: 10 ± 8% 2: 32 ± 7% 3: 47 ± 4% 4: 34 ± 9% | (Figueiro, Rea, and Bullough 2006) [150] |
n = 21 mean age 28.0 ± 9.9 years | 1. Computer monitor 7 lx 2. Computer monitor 7 lx + 40 lx blue safety glasses (peak λ ~470 nm) | 2 h (11:00 p.m.–1:00 a.m.) | N/A | Computer monitor 7 lx + orange-tinted glasses (<525 nm ~0) | Laboratory | MEL in saliva | 1: −11% NS 2: −30% * | (Figueiro et al. 2011) [130] |
n = 116 study 1 n = 104, study 2 n = 12 (18–30 years) | <200 lx | overnight illumination Study 1: 9–10 days Study 2: 14 days | 4100 K | ˂3 lx | Laboratory | MEL in plasma | Exposure during sleep: ~−50% in 85% trial exposure before bedtime: SUP MEL, later MEL onset in 99.0% of individuals and shortened MEL duration by ~90 min | (Gooley et al. 2011) [131] |
n = 9 M = 9 mean age 22.11 ± 0.69 years | 200 lx 500 lx 1000 lx 5000 lx 10,000 lx | 3 h (6:00–9:00 a.m.) | N/A | ˂200 lx | Laboratory | MEL in plasma | 200 lx NS ˃500 lx *, first hour of exposure ~35–50% | (Hashimoto et al. 1996) [124] |
n = 22 M=22 mean age 30.95 ± 4.15 years | 2 types of smartphones: LED with blue light, LED with suppressed blue light | 150 min (7:30–10:00 p.m.) | N/A | <3 lx | Laboratory | MEL in blood serum | LED with blue light: lower levels and later onset of MEL secretion than LED with SUP blue light MEL between groups: NS | (Heo et al. 2017) [125] |
n = 34, F young (n = 13), mean age 24 ± 3 years F postmenopausal (n = 21), mean age 57 ± 5 years | 456 nm: ~11.4 lx (3.8 μW/cm2) 29.4 lx (9.8 μW/cm2) 548 nm: 84 lx (28 μW/cm2) 186 lx (62 μW/cm2) | 30 min during the rising phase of melatonin synthesis | Monochromatic light: 456 nm 548 nm
| 0 lx | Laboratory | MEL in plasma | 456 nm, postmenopausal women: ~11.4 lx: −1.4 ± 5% NS 29.4 lx: −12.5 ± 4% NS Young women ~11.4 lx: −18.4 ± 4.8% * 29.4 lx: −25.5 ± 6.4% * 548 nm: SIGN SUP in both age group, NS difference between age groups | (Herljevic et al. 2005) [120] |
n = 11 M = 11 mean age 21.2 ± 0.9 years | 1. Non-visor: 500 lx 2. red visor: 160 lx 3. blue visor: 160 lx | 2–4 h (11:00 p.m.–3:00 a.m.) | 4200 K | ˂15 lx | Laboratory | MEL in saliva | 2-h exposure: 1: −57.0 ± 26.6% 2: -20.3 ± 32.1% * to non-visor 3: −31.1 ± 41.5% 4 h exposure: 1: −52.6 ± 22.4% 2: −7.7 ± 3.3% * 3: −3 ± 67.6% * | (Higuchi et al. 2011) [126] |
n = 12 M = 12 mean age 21.3 ± 1.1 years | 200 lx | 1.5 h (1:00–2:30 a.m.) | Fluorescent lamps: 2300 K 3000 K 5000 K | <10 lx | Laboratory | MEL in saliva | 5000 K: * 3000 K: * 5000 K more than 3000 K 2300 K: NS | (Kozaki et al. 2008) [127] |
(Experiment 2) n = 16 M = 9, F = 7 (19–28 years) | 200 lx | 4 h (10:00 p.m.–2:00 a.m.) | L1—1600 K L2—1950 K L3—2750 K L4—3900 KL5—6100 K L6—7100 K L7—14,000 K | <0.1 lx | Laboratory | MEL in saliva | Small MEL SUP under CCT <2000 K and strong MEL SUP with CCT ≥3900 K AUC under L4–L7 were SIGN lower than under L1 and AUCs under L3-L7 were SIGN smaller than under L2 | (Kraneburg et al. 2017) [141] |
n = 6 M = 4, F = 2 mean age 32.3 + 6.2 years | 200 lx 400 lx 600 lx | 3 h (12:00–03:00 a.m.) | N/A | ˂10 lx | Laboratory | MEL in plasma | 200 lx: −21% NS 400 lx: −50% * 600 lx: −65% * | (McIntyre et al. 1989) [145] |
n = 18 M = 6; F = 12; mean age 23.2 ± 3.3 years | Evening light: orange (OL) ~100 lx; blue-enriched (BL) ~500 lx Morning light: mixed blue-enriched (MBL) 750 lx; control (CON) 40 lx | EL: 30 min (10:00–10:30 p.m.) ML: 3 h (8:00–11:00 a.m.)
| OL—1500 K BL—6500 K DL—2700 K MBL—3,537 K CON—2600 K | Dim light (DL) <7 lx
| Laboratory and home settings | MEL in saliva
| Evening light: BL to D: * OL to DL: * OL to BL: * Phase shifts greater under CON than MBL, phase delays after 3 days: MBL to CON * phase advances: NS
| (Münch et al. 2017) [142] |
n = 24 12 adolescents: M = 3, F = 9 mean age 16.5 ± 1.9 years 12 adults: M = 2, F = 10 mean age 46 ± 5.2 years | 295 lx for 2700 K 209 lx for 5600 K (CS at the eye level = 0.25)
| 4 h (11:00 p.m.–3:00 a.m.) | Blue light, 2700 K 5600 K
| <5 lx | Laboratory | MEL in saliva | Greater MEL SUP for longer exposure duration, SIGN interaction between light spectrum and age Adolescents: 5600 K: −43 ± 4% * 2700 K: −29 ± 4% * Adults: 5600 K: −33% ± 3% * 2700 K: −33% ± 2% * | (Nagare, Plitnick and Figueiro 2019) [136] |
n = 41 18 adolescents (13–18 years) 23 adults (24–55 years) | 40–1000 lx (CS = 0.07, 0.14, 0.30, 0.50) | 0.5–3.0 h (11:00 p.m.–2:00 a.m.) | White light, 2700K 6500 K | <5 lx | Laboratory | MEL in saliva | SIGN effects of light intensity, spectrum, exposure duration; effect of light diminishes with increasing exposure duration for age groups and spectra. 6500 K: −24.7 ± 1% * 2700 K: −18.4 ± 1% * | (Nagare et al. 2019) [137] |
n = 54, study 1: M = 22 (19–34 years), F = 21 (20–56 years) study 2: M = 4 (27–58 years), F = 7 (25–51 years) | Study 1: 200 lx study 2: 500 lx | 1h (12:00–1:00 a.m.) | 5000 K | 10–20 lx | Laboratory | MEL in plasma | Study 1: M: 16,9% F: 14,5% study 2: M: 35% F: 45% NS differences between the sexes | (Nathan, Burrows, and Norman 1997) [151] |
n = 10 M = 5, F = 5 mean age 25.0 ± 2.5 years | 200 lx 500 lx 1000 lx 3000 lx | 1h (12:00–1:00 a.m.) | 5000 K | 10–20 lx | Laboratory | MEL in plasma | 200 lx: −17% NS 500 lx: −40% * 1000 lx: −56% * 3000 lx: −74% * No differences between the sexes | (Nathan et al. 2000) [143] |
n = 528; dark LAN group n = 383 LAN group n = 145 Seniors (min 60 years) mean age 72.8 years | LAN group ≥ 3 lx | Continuous overnight exposure | N/A | Dark LAN <3 lx | Home settings | aMT6s in urine | LAN 6.8 g (4.3–10.5); Dark LAN group: 6.5 g (3.9–9.5); NS | (Obayashi et al. 2013) [119] |
n = 56 M = 27, F = 29 mean age 20.8 ± 2.6 years | 10, 30, 50, 100, 200, 400, and 2000 lx | 5 h (4 h before sleep and 1 h after sleep start) | 4100 K | <1 lx | Laboratory | MEL in saliva | −50% * at group level ~24.6 lx; high variability for individuals: −50% * from 6 to 350 lx | (Phillips et. al. 2019) [117] |
n = 36, each experiment n = 12 M = 29, F = 7 mean age 21.91 ± 2.03 years | 100 lx, partial illumination of the retina | 4 h (12:00–4:00 a.m.) | N/A | <10 lx | Laboratory | MEL in saliva | −22% * after temporal and −58% * after nasal exposure | (Rüger et al. 2005) [138] |
n = 16 M = 9; F = 7 mean age 36.2 ± 8.6 years | ~175 lx | 3 h 2 h before and 1 h after habitual bedtime | White light, similar CCT 2700 K 2 spectral powers: low 52.03 µW/cm2 high 90.85 µW/cm2 | <5 lx | Laboratory | MEL in saliva | High MEF: ~−50% * low MEF: NS | (Souman et al. 2018) [146] |
n = 22 M = 18, F = 4 mean age 27.0 ± 7.0 years | 0.70–65 µW/cm2 | 30 min (11:30 p.m.–2:30 a.m.) CT 16–18 | Monochromatic light, λmax 424, 456, 472, 496, 520, and 548 nm | No light exposure | Laboratory | MEL in plasma | MEL concentrations SUP in a dose-dependent manner. No SIGN MEL SUP at the lowest irradiances (0.70–3.3 µW/cm2) of 520 nm | (Thapan, Arendt, and Skene 2001) [144]
|
n = 6 M = 6 (18–22 years, mean age 20.2 years) | 250 lx 500 lx 1000 lx 2500 lx | 3 h individually determined 1h before MEL onset | N/A | <50 lx | Laboratory | MEL in plasma | Complete MEL SUPPR compared to CON in all treatments | (Trinder et al. 1996) [128] |
n = 33 M = 33 study 1 n = 17 study 2 n = 16 (22.6 ± 2.2 years) | 1. Short-wavelength attenuated polychromatic white light (SWL): 193 lx 2. Full-spectrum light (FWL): 256 lx | 3 nights, overnight exposure (11:00 p.m.–7:00 a.m.) | 3000 K | 3 lx | Laboratory and home settings | MEL in saliva aMT6s in urine | SWL: −6 ± 4% NS FWL: −45 ± 6% * SWA to CON * | (Van De Werken et al. 2013) [129] |
n = 6 (19–37 years) | 8.1 log photons/cm2·s 9.2 log photons/cm2·s 10.3 log photons/cm2·s | 1 h (10:00–11:00 p.m.)
| 460 nm | Complete darkness | Laboratory | MEL in saliva | Threshold for human melatonin suppression ~10 log photons/cm2·s at 460 nm | (Vartanian et al. 2015) [132] |
n = 9 M = 6; F = 3 mean age 26.3 ± 4.2 (22–33 years) | 1. 130 lx 2. 130 lx 3. 500 lx 4. 500 lx 5. 500 lx | 30 min (10:30–11:00 p.m.) | 1. 2000 K 2. 6000 K 3. 6000 K 4. 5000 K 5. 2800 K | <10 lx | Laboratory | MEL in saliva | 1: NS 2–5: * | (Wahnschaffe et al. 2013) [147] |
n = 10 M = 6, F = 4 18–41 years | 500–1000 lx full spectrum 500–1000 lx green light | 1 h (2:00–3:00 a.m.) | N/A | 20–50 lx full spectrum (dim) | Laboratory | MEL in saliva | All light treatments SIGN different from CON. None of the treatment conditions SIGN different from each other | (Whitmore, French, and Fischer 2001) [149] |
n = 13 mean age 18.9 ± 5.2 years | Tablet + blue LED 59 ± 5.0 lx tablet only 18 ± 3. 8 lx | 1–2 h (11:00 p.m.–1:00 a.m.) 3 weekends, 1 week apart | blue light λmax ~470 nm | Tablet + orange-tinted glasses 9.8 ± 1.9 used as control | Laboratory | MEL in saliva | 1 h exposure: Tablet + blue LED: −48 ± 4% * Tablet only: −7 ± 4% NS 2 h exposure: Tablet + blue LED: −66 ± 4% * Tablet only: −23 ± 6% * | (Wood et al. 2013) [133] |
n = 15 M = 5, F = 10 mean age 31.8 ± 11.9 years | 130 µW/cm2 (received by each eye) | 2 h (12:00–2:00 a.m.) | 1. 660 nm 2. 595 nm 3. 525 nm 4. 497 nm 5. 470 nm | No light | Laboratory | MEL in saliva | 1: −5% NS 2: −10% NS 3: −70% * 4: −80% * 5: −65% *
| (Wright and Lack 2001) [148] |
n = 23 mean age 27.8 ± 8.91 (18–44 years) | 3 lx 106 lx 9100 lx | 6–5-h pulse | Cool light | Dim light | Laboratory | MEL in plasma | 3 lx: −11% N/A 106 lx: −88% N/A 9100 lx: −98% N/A | (Zeitzer et al. 2000) [134] |