This is a guest blog post by Mariana Figueiro, Light and Health Program Director at the Lighting Research Center (LRC) and Associate Professor at Rensselaer Polytechnic Institute. Her talk at TEDMED 2014 reveals, surprising facts about the effect of light – its presence, its absence, and its patterns – on human health.
All creatures, great and small, are governed by the natural 24-hour, light-dark cycle. Every cell and physiological system in plants and animals exhibits a circadian cycle. In the absence of a regular 24-hour light-dark cycle, a circadian cycle in humans runs with a period close to, but not exactly, 24 hours. Daily exposures to morning light, especially blue light, reset the timing of our biological clock and synchronize our circadian rhythms to the local sunrise and sunset. Disruption of these circadian rhythms resulting from exposure to irregular light-dark patterns or exposure to light at the wrong time of day can compromise health. For example, it has been shown in animal models that circadian disruption is linked to increased risk for diabetes, obesity, cardiovascular disease and even cancer.1-5 Therefore, receiving the right light at the right time can be the key to good sleep, good health and wellbeing. We are swimming in an ocean of light, but like fish that take water for granted, we generally pay little attention to our environmental light. Light is the conductor of our internal symphony, influencing when we sleep and wake, our cognitive abilities, how much we eat, and even how well our medicine works.6-8
Recognizing the impact of light on the individual and on a global scale, the United Nations has proclaimed 2015 as the International Year of Light, citing that light plays a vital role in our daily lives, has revolutionized medicine, and that light-based technologies promote sustainable development and provide solutions to global challenges in energy, education, agriculture and health.
Just last year, the Nobel Prize in Physics was presented to the inventors of the blue LED, Isamu Akasaki, Hiroshi Amano and Shuji Nakamura.
At the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute, we focus on the myriad effects of light on human health at all ages. We are working on developing a lighting system that can be used with premature infant incubators in the NICU to provide cycled lighting, which has been shown to improve health outcomes in premature infants. We are also investigating effective ways to deliver light as a treatment to improve sleep, depression and agitation in Alzheimer patients.
Beyond the long-term health benefits of synchronizing our circadian rhythms to the local time on Earth, light has an acute effect, an alerting boost, like a cup of coffee, which can help give us the energy we need when we wake up in the morning and also help to fight the post-lunch dip. We are trying to figure out how red light impacts alertness and performance during the day and at night. This could benefit shift workers, because red light can increase alertness without affecting melatonin levels. The suppression of melatonin by light at night has been implicated in health problems such as breast cancer in these shift workers.
Aside from the special light needs of these select populations, there is every reason to believe that introducing a regular 24-hour pattern of light and dark by modifying the amount of electric lighting we are exposed to daily, could improve the health and productivity of everyone. We are currently looking at the impact of artificial light and natural daylight on the health and wellbeing of federal employees working in buildings owned and leased by the U.S. General Services Administration. To further study this question in the home environment, we are also developing a lighting system that could be incorporated into the design of Swedish homes. The availability of daylight in Sweden during winter months is very limited, and so we are designing a “healthy home” using lighting principles that will promote health and wellbeing not only in Swedish homes, but in other places where daylight availability is limited. The system will provide cycled electric lighting with cool, high light levels during the day and warm, low levels at night. This type of cycled lighting is ideal for circadian health, encouraging restful sleep at night and increased alertness and performance during the day – not to mention many other general health benefits, such as improved mood and reduced risk of diabetes, obesity, cardiovascular disease and cancer.1-5, 9
An important component of the healthy home concept is the “Daysimeter” – a personal circadian light measurement device. The Daysimeter measures how much circadian light an individual receives over a 24-hour period, and then via smartphone it automatically adjusts lighting in the home and office to provide the ideal type of light needed to support health and wellbeing.
Imagine wearing this small, unobtrusive device, that would measure a dark, snowy day in January with little or no circadian-effective light, and then adjust the lighting in the morning to provide cool, high light levels to entrain you to the 24-hour solar day and give you an alerting boost of energy. In the afternoon, light levels would be adjusted based on how much light was received during the day, as measured by the Daysimeter. In the evening, the lighting would automatically adjust to provide warm, low levels of soothing light to ensure restful sleep. Thanks to advances in LED technology, the healthy home of the future could realistically happen in the next decade. We have developed the 24-hour lighting scheme and Daysimeter and have completed extensive testing in the lab and in the field, and are now working to study the real-world effects of this lighting scheme with people living their normal, daily lives. Today, many people think of light as just part of a building. In the future, we believe light will become more personalized, customizable, and tailored to the needs of each individual. Perhaps 2015 is the year that we will see the world in a new light.
References 1. Leproult R, Holmback U and Van Cauter E. Circadian misalignment augments markers of insulin resistance and inflammation, independently of sleep loss. Diabetes. 2014; 63: 1860-9. 2. Ye HH, Jeong JU, Jeon MJ and Sakong J. The association between shift work and the metabolic syndrome in female workers. Annals of Occupational and Environmental Medicine. 2013; 25: 33. 3. Young ME and Bray MS. Potential role for peripheral circadian clock dyssynchrony in the pathogenesis of cardiovascular dysfunction. Sleep Medicine. 2007; 8: 656-67. 4. Maemura K, Takeda N and Nagai R. Circadian rhythms in the CNS and peripheral clock disorders: role of the biological clock in cardiovascular diseases. Journal of Pharmacological Sciences. 2007; 103: 134-8. 5. Schernhammer ES, Laden F, Speizer FE, et al. Rotating night shifts and risk of breast cancer in women participating in the Nurses’ Health Study. Journal of the National Cancer Institute. 2001; 93: 1563-8. 6. Hrushesky W. Circadian timing of cancer chemotherapy. Science. 1985; 228: 73-5. 7. Hrushesky W, Wood P, Levi F, et al. A recent illustration of some essentials of circadian chronotherapy study design. Journal of Clinical Oncology. 2004; 22: 2971-2. 8. Zhang R, Lahens NF, Ballance HI, Hughes ME and Hogenesch JB. A circadian gene expression atlas in mammals: Implications for biology and medicine. Proceedings of the National Academy of Sciences. 2014; 111: 16219-24. 9. Figueiro MG, Plitnick B, Lok A, et al. Tailored lighting intervention improves measures of sleep, depression and agitation in persons with Alzheimer’s disease and related dementia living in long-term care facilities. Clinical Interventions in Aging. 2014; 9: 1527-37.
Watch Mariana’s talk from TEDMED 2014