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Comparative Study 2011; 32(2): 158-163 PubMed PMID: 21552190 Citation  Keywords:  Adult, Circadian Rhythm:physiology, Computers, Humans, Light, Lighting, Melatonin:metabolism, Saliva:metabolism, Sleep:physiology, Students, Universities,.   

OBJECTIVES: Self-luminous electronic devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression. Melatonin suppression resulting from exposure to light at night has been linked to increased risk for diseases. The impact of luminous cathode ray tube (CRT) computer monitors on melatonin suppression was investigated.

DESIGN: Twenty-one participants experienced three test conditions: 1) computer monitor only, 2) computer monitor viewed through goggles providing 40 lux of short-wavelength (blue; peak λ ≈ 470 nm) light at the cornea from light emitting diodes (LEDs), and 3) computer monitor viewed through orange-tinted safety glasses (optical radiation <525 nm ≈ 0). The blue-light goggles were used as a "true-positive" experimental condition to demonstrate protocol effectiveness; the same light treatment had been shown in a previous study to suppress nocturnal melatonin. The orange-tinted glasses served as a "dark" control condition because the short-wavelength radiation necessary for nocturnal melatonin suppression was eliminated. Saliva samples were collected from subjects at 23:00, before starting computer tasks, and again at midnight and 01:00 while performing computer tasks under all three experimental conditions.

RESULTS: Melatonin concentrations after exposure to the blue-light goggle experimental condition were significantly reduced compared to the dark control and to the computer monitor only conditions. Although not statistically significant, the mean melatonin concentration after exposure to the computer monitor only was reduced slightly relative to the dark control condition.

CONCLUSIONS: Additional empirical data should be collected to test the effectiveness of different, brighter and larger screens on melatonin suppression....

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Clinical Trial 2010; 31(1): 92-96 PubMed PMID: 20150866 Citation  Keywords:  Adolescent, Biological Clocks:physiology, Circadian Rhythm:physiology, Eyeglasses, Female, Humans, Light, Lighting:adverse effects, Male, Melatonin:metabolism, Population, Radio Waves, Schools, Sleep Disorders, Circadian Rhythm:etiology, Students, Time Fa.   

OBJECTIVE: Circadian timing affects sleep onset. Delayed sleep onset can reduce sleep duration in adolescents required to awake early for a fixed school schedule. The absence of short-wavelength ("blue") morning light, which helps entrain the circadian system, can hypothetically delay sleep onset and decrease sleep duration in adolescents. The goal of this study was to investigate whether removal of short-wavelength light during the morning hours delayed the onset of melatonin in young adults.

METHODS: Dim light melatonin onset (DLMO) was measured in eleven 8th-grade students before and after wearing orange glasses, which removed short-wavelength light, for a five-day school week.

RESULTS: DLMO was significantly delayed (30 minutes) after the five-day intervention, demonstrating that short-wavelength light exposure during the day can be important for advancing circadian rhythms in students.

CONCLUSIONS: Lack of short-wavelength light in the morning has been shown to delay the circadian clock in controlled laboratory conditions. The results presented here are the first to show, outside laboratory conditions, that removal of short-wavelength light in the morning hours can delay DLMO in 8th-grade students. These field data, consistent with results from controlled laboratory studies, are directly relevant to lighting practice in schools....

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Clinical Trial 2005; 26(5): 493-498 PubMed PMID: 16264413 Citation  Keywords:  Adult, Circadian Rhythm:physiology, Humans, Light, Lighting, Male, Melatonin:blood, Middle Aged, Photic Stimulation, Pupil:physiology, Retina:physiology, Signal Transduction:physiology,.   

OBJECTIVES: Published data, both on nocturnal melatonin suppression in humans and on widely accepted retinal structure and function, suggest that spectral opponency plays a role in human circadian phototransduction. We directly test subadditivity, implied by spectral opponency, in human circadian phototransduction in response to nearly monochromatic and to polychromatic light.

METHODS: Adult male human subjects were exposed for 60 minutes to two intensities each of two lighting conditions, during nighttime experimental sessions. One condition consisted of light from mercury vapor lamps (450 and 1050 lx), and one condition consisted of light from these lamps filtered such that only the spectral line from this lamp at 436 nm was presented to subjects (7.5 and 15 lx).

RESULTS: Melatonin suppression from the filtered illumination at 436 nm alone was greater than mercury lamp illumination (containing energy at 436 nm in addition to other wavelengths), even when the sources exposed subjects' retinae to equal amounts of irradiance at 436 nm.

CONCLUSION: This direct test of subadditivity, together with evidence from neuroanatomy, supports the inference that spectral opponency is a fundamental characteristic of human circadian phototransduction....

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Comparative Study 2002; 23(4): 345-350 PubMed PMID: 12195239 Citation  Keywords:  Aging:metabolism, Animals, Antioxidants:metabolism, Darkness, Hippocampus:enzymology, Lighting, Lipid Peroxidation:physiology, Male, Pineal Gland:physiology, Rats, Rats, Wistar, Receptors, N-Methyl-D-Aspartate:metabolism, Superoxide Dismutase:metabolism,.   

OBJECTIVES: To investigate the effects of pinealectomy on lipid peroxidation, antioxidant status and NMDA receptor subunits 2A and 2B concentrations in hippocampus.

DESIGN: Forty-eight male Wistar-albino rats were used.

SETTINGS: Animals were divided into three groups: 24 h dark throughout the study (highest melatonin release), 24 h light exposure (light-induced functional pinealectomy) and 12 h light/12 h dark exposure (control group). Thereafter, each group was divided into two groups as young and old animals.

RESULTS: There was an increase in NR2A and NR2B concentration in DY group compared to all other treatments. CuZn and Mn SOD activities were found to be increased in CO compared to CY group. Continual light exposure for 4 weeks did not change neural CuZn and Mn SOD activities. In old rats, light exposure reduced the activities of both CuZn and Mn SOD relative to those in the young animals. In addition, CuZn and Mn SOD activities were higher in dark exposed rats than in those in the continual light exposed or LD 12:12 rats. GSH-Px activity was found elevated in the DY rats compared to the CY groups. MDA levels were significantly higher in the CO than in the CY group.

CONCLUSIONS: NR2A and NR2B receptor concentrations in hippocampus of the rats maintained in dark showed significant increases compared to the control and functional pinealectomy groups but there was no significant increase in lipid peroxidation....

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Journal Article 2002; 23(Suppl 2): 57-60 PubMed PMID: 12163850 Citation  Keywords:  Breast Neoplasms:epidemiology, Circadian Rhythm, Female, Humans, Light:adverse effects, Lighting, Risk Factors,.   

: Risk of breast cancer varies by about 5-fold among societies, and incidence and mortality have been increasing worldwide for many decades. Migrants from low-risk Asian societies to the U.S. suffer elevated risk of breast cancer in their own lifetimes, and the second or third generation Asian-Americans attain the high risk of the multi-generational European immigrants [1,2]. Something about a modern Western lifestyle apparently increases risk dramatically. Madigan et al. [3] estimate that 41% of the new U.S. cases of breast cancer are explained by "known risk factors"; these include the reproductive factors of age at first birth, menarche, menopause. They ascribe about 30% to reproductive factors when they are analyzed alone. "High income" is estimated to account for about 19% when analyzed by itself. The 41% is an analysis taking all the factors together, and since they are related, the total is less than the sum of estimates for the individual items. By itself, "High income" has no biological interpretation and must reflect attributes of lifestyle and/or environment that increase risk. So, the proportion of breast cancer cases in the U.S. that can be accounted for by known biological risk factors is about one third. Therefore, at least half of breast cancer risk in the U.S., and other Westernized/industrialized societies, is in excess of that found in non-industrialized societies and is without any agreed-upon explanation. Many candidate factors exist, each with a cadre of proponents. The sum of these may turn out to explain the bulk of the excess risk in modern societies. On the other hand, they may not, and worse, may fall woefully short....

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Journal Article 2002; 23(Suppl 2): 14-16 PubMed PMID: 12163842 Citation  Keywords:  Humans, Light:adverse effects, Lighting, Physical Phenomena, Physics, Sunlight:adverse effects,.   

: The physical properties of light, both natural and artificial, play a significant role in its interaction with humans. Although there is a yet-to-be-explained duality between light as waves and light as photons, we do understand many of the characteristics of light that affect living things. Here I review the general history of light and its properties, especially those that affect human health....

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