Does architectural lighting contribute to breast cancer?
ABSTRACT There is a growing interest in the role that light plays on nocturnal melatonin production and, perhaps thereby, the incidence of breast cancer in modern societies. The direct causal relationships in this logical chain have not, however, been fully established and the weakest link is an inability to quantitatively specify architectural lighting as a stimulus for the circadian system. The purpose of the present paper is to draw attention to this weakness.
We reviewed the literature on the relationship between melatonin, light at night, and cancer risk in humans and tumor growth in animals. More specifically, we focused on the impact of light on nocturnal melatonin suppression in humans and on the applicability of these data to women in real-life situations. Photometric measurement data from the lighted environment of women at work and at home is also reported.
The literature review and measurement data demonstrate that more quantitative knowledge is needed about circadian light exposures actually experienced by women and girls in modern societies.
Without such quantitative knowledge, limited insights can be gained about the causal relationship between melatonin and the etiology of breast cancer from epidemiological studies and from parametric studies using animal models.
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ABSTRACT: Background: There is convincing evidence that circadian disruption mediated by exposure to light at night promotes mammary carcinogenesis in rodents. The role that light at night plays in human breast cancer etiology remains unknown. We evaluated the relationship between estimates of indoor and outdoor light at night and the risk of breast cancer among members of the California Teachers Study. Methods: Indoor light-at-night estimates were based on questionnaire data regarding sleep habits and use of nighttime lighting while sleeping. Estimates of outdoor light at night were derived from imagery data obtained from the US Defense Meteorological Satellite Program assigned to geocoded addresses of study participants. Analyses were conducted among 106,731 California Teachers Study members who lived in California, had no prior history of breast cancer, and provided information on lighting while sleeping. Five thousand ninety-five cases of invasive breast cancer diagnosed 1995-2010 were identified via linkage to the California Cancer Registry. We used age-stratified Cox proportional hazard models to calculate hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for breast cancer risk factors and neighborhood urbanization and socioeconomic class. Results: An increased risk was found for women living in areas with the highest quintile of outdoor light-at-night exposure estimates (HR = 1.12 [95% CI = 1.00-1.26]; test for trend, P = 0.06). Although more pronounced among premenopausal women (HR = 1.34 [95% CI = 1.07-1.69]; test for trend, P = 0.04), the associations did not differ statistically by menopausal status (test for interaction, P = 0.34). Conclusions: Women living in areas with high levels of ambient light at night may be at an increased risk of breast cancer. Future studies that integrate quantitative measurements of indoor and outdoor light at night are warranted.Epidemiology (Cambridge, Mass.) 07/2014; 25(5). DOI:10.1097/EDE.0000000000000137 · 6.18 Impact Factor
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ABSTRACT: Background Light therapy has shown great promise as a nonpharmacological method to improve symptoms associated with Alzheimer’s disease and related dementias (ADRD), with preliminary studies demonstrating that appropriately timed light exposure can improve nighttime sleep efficiency, reduce nocturnal wandering, and alleviate evening agitation. Since the human circadian system is maximally sensitive to short-wavelength (blue) light, lower, more targeted lighting interventions for therapeutic purposes, can be used. Methods The present study investigated the effectiveness of a tailored lighting intervention for individuals with ADRD living in nursing homes. Low-level “bluish-white” lighting designed to deliver high circadian stimulation during the daytime was installed in 14 nursing home resident rooms for a period of 4 weeks. Light–dark and rest–activity patterns were collected using a Daysimeter. Sleep time and sleep efficiency measures were obtained using the rest–activity data. Measures of sleep quality, depression, and agitation were collected using standardized questionnaires, at baseline, at the end of the 4-week lighting intervention, and 4 weeks after the lighting intervention was removed. Results The lighting intervention significantly (P<0.05) decreased global sleep scores from the Pittsburgh Sleep Quality Index, and increased total sleep time and sleep efficiency. The lighting intervention also increased phasor magnitude, a measure of the 24-hour resonance between light–dark and rest–activity patterns, suggesting an increase in circadian entrainment. The lighting intervention significantly (P<0.05) reduced depression scores from the Cornell Scale for Depression in Dementia and agitation scores from the Cohen–Mansfield Agitation Inventory. Conclusion A lighting intervention, tailored to increase daytime circadian stimulation, can be used to increase sleep quality and improve behavior in patients with ADRD. The present field study, while promising for application, should be replicated using a larger sample size and perhaps using longer treatment duration.Clinical Interventions in Aging 09/2014; 9:1527-37. DOI:10.2147/CIA.S68557 · 1.82 Impact Factor
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ABSTRACT: Technologies are needed to provide information about the state of our circadian system to our conscious awareness such that we can take appropriate action to avoid and to correct light-induced circadian disruption. In addition to the implicit promises of solid-state lighting to improve energy efficiency and the quality of the visual environment, solid-state lighting also promises to maintain our health and well-being by precisely tailoring light and dark throughout the 24-hour day.Proceedings of SPIE - The International Society for Optical Engineering 02/2011; DOI:10.1117/12.876409 · 0.20 Impact Factor