As evening approaches in the dementia ward at the Albany County Nursing Home, patients' irritability and confusion rises. Come nighttime, many residents have problems sleeping — wandering, wheeling or perhaps falling in the halls.
So two years ago, health researchers installed what the home's nurse manager Karen Pitcher calls "the miracle table," a repurposed flat screen TV that emits a bluish-white light. They gathered residents around it at mealtimes, and allowed them to congregate there whenever they pleased from 7 a.m. to 6 p.m. The goal was to help stimulate the residents' circadian rhythms — the hormones that ebb and flow according to light and other signals — and help correct the sleep disorders that are all too common among the ward's elderly patients, especially those with dementia.
The miracle table worked some wonders. What happened wasn't a complete reversal of symptoms, but was significant nonetheless for many patients.
One person who had been almost completely incontinent started to control her toileting with little assistance and started to "look around and perk up and do things again," Pitcher says. "I had another patient who [had often been] up fighting from 3 a.m. to 11 a.m. and stopped."
In addition, patients fell less frequently and the light had a calming effect. "They liked sitting there because it was nice and warm and bright," she says.
The light table is the brainchild of Mariana Figueiro, PhD, professor and Light and Health program director at the Lighting Research Center at Rensselaer Polytechnic Institute. The data from the study on the Albany ward, which appeared in Lighting Research and Technologyopens in new window in 2015, backed up Pitcher's observations: Patients who used the table had a 10 percent increase in sleep efficiency, and had a significant reduction in symptoms of agitation and depression.
Scientists have long known that both daylight and manufactured light delivered at the right time can have a powerful influence on our circadian rhythms, which are critical to mood, sleep and cognitive function. But new research is pinpointing how manipulating different wavelengths of electric light might be used to treat circadian disorders.
Research is also showing how light can be a boon when exposure matches a person's needs. In 2014, scientists at the University of Illinois at Urbana-Champaign, found that exposure to daylight in office settings increased workers' productivity and physical activity (Journal of Clinical Sleep Medicineopens in new window, 2014).
Conversely, too much light at the wrong time, perhaps from computer screens at night, urban light pollution and night shift workers' use of light at work, can disrupt circadian rhythms, increasing the risk of mood disorders, obesity and even some cancers, according to a reviewopens in new window by Tracy Bedrosian, PhD, of the Salk Institute for Biological Studies (Annual Review of Physiologyopens in new window, 2015).
In response, scientists, architects and lighting manufacturers are coming up with ways to help better sync our physical environments with our internal clocks. Soon, many experts say, carefully manipulating the human-made light that surrounds us will become a common step toward improving mental and physical health and well-being. That may be particularly helpful for those most vulnerable to sleep disorders due to biological and lifestyle factors, including older adults, adolescents and shift workers.
"We're only at the very beginning of our understanding, but we're learning a lot more about the positive and negative effects of light," Figueiro says. "We have new technology and have the ability to manipulate lighting color and intensity, and people can see it being applied. You'll be hearing many more people talking about electric light as an important component of the built environment in terms of health."
The right light at the right time
We receive light via three types of photoreceptors: rods that allow us to see in low light levels (nighttime conditions), cones that allow us to see in high light levels (daytime conditions) and a new class of photoreceptor discovered in 2002 known as intrinsically photosensitive retinal ganglion cells (ipRGCs). The ipRGCs, which also receive input from rods and cones, carry signals from the retinae through a different pathway, known as the retino-hypothalamic tract, to the biological clock in the brain that generates and regulates our circadian rhythms.
Different parts of the light spectrum stimulate the retinae — and thus the brain — in various ways. The ipRGCs are most sensitive to short-wavelength radiation, which we generally perceive as bluish-white light. Thanks to the invention of energy efficient light-emitting diode (LED) lights, which can deliver various combinations of light colors, we're more easily able to tap into these powerful wavelengths of light indoors.
Research is also showing that the circadian system is not the only pathway through which light can affect our physiology and behavior. Short-wavelength (blue) light is most effective at suppressing melatonin, a hormone produced by the pineal gland at night that signals the human body that it's time to sleep. Instead, blue light at night signals to our brains that it's time to be alert. Long wavelengths, however, appear to boost alertness without affecting nocturnal melatonin. For example, a study by Figueiro and colleagues suggests that long wavelength (red) light, which LEDs can also deliver, may help keep us alert and productive at night and throughout the day, which may be helpful during a postlunch dip (Behavioral Brain Researchopens in new window, 2014).
Light and the aging body
Those relationships aren't as clear-cut in older adults, however. As people age, their sleep-wake patterns often make unwelcome shifts, with up to 70 percent of older adults experiencing sleep disturbances or disorders. That may be because of underlying changes in the circadian system. Researchers have found that older adults have less activity in the suprachiasmatic nucleus, the brain area that controls circadian cycles. Blue light has less of a stimulating effectopens in new window on areas of their brains involved with alertness and cognition, according to a 2014 fMRI study in Sleep by Véronique Daneault of the University of Montreal, and colleagues. Older adults produce less melatonin overall than younger ones, and it can take longer for older adults to fall and stay asleep. In addition, lifestyle changes, such as cutting back on work, exercise and social activity can also contribute to sleep differences, and physical changes to the eye such as cataracts and macular degeneration can make it harder to receive light.
People with Alzheimer's or other types of dementia are even more likely than other older adults to have disrupted sleep schedules, including night wanderings. Studies suggest their circadian rhythms become less regular and more delayed — meaning they may have trouble falling asleep — and melatonin levels decrease. They are also more likely to suffer from degeneration of their ganglion cells.
A number of studies suggest that disordered sleep may contribute to developing disease. Scientists who disturbed sleep cycles in mice, similar to what humans experience during jet lag, discovered that the animals' brains produced less glutathione, an antioxidant that helps protect against neuron damage and brain inflammation (Journal of Alzheimer's Disease, 2015).
Sleep problems are also associated with the buildup of beta-amyloid, the protein that can form clumps and kill brain cells — a hallmark of Alzheimer's disease. A 2013 JAMA studyopens in new window by Adam P. Spira, PhD, of the Johns Hopkins Bloomberg School of Public Health used PET to show that poor and short sleep were associated with an increase of beta-amyloid. Another study of older adults in Nature Neuroscienceopens in new window in June 2015 by Bryce Mander, PhD, of the University of California, Berkeley, showed that healthy older adults with the highest buildup of the protein had poorer sleep quality and performed worse on memory tests. Some scientists suspect that sleep helps flush away beta-amyloid proteins and other potentially toxic buildups (Science, 2013).
Living in a long-term care center can also make sleep challenging for patients. They may spend more time in bed, and encounter noise and light at inopportune times. They may also have difficulty getting outside for a daily dose of sunlight that would signal their brains that is it daytime and that it is time to be awake. In addition, many care centers are dimly lit, Figueiro says, adding that older people in care homes are often in "the worst possible environment" for alertness during the day and sleeping at night.
One way to help jump-start circadian cycles is sitting in front of a simple light box. However, getting anyone — let alone seniors with dementia — to regularly bask in the sometimes uncomfortably bright light can be challenging.
"When we're talking about using light to benefit health, we're not talking about simply immediate effects. We're talking about the total daily pattern of light," says Jennifer Veitch, PhD, a psychologist at the National Research Council of Canada who researches how light affects human well-being and productivity.
That's where measured doses of indoor light come in, delivered at varying intensities in convenient locations throughout the living environment. Even modest lighting remedies — such as brighter floor and wall lamps during waking hours — can help reduce symptoms of agitation and dementia in long-term care settings, as Figueiro and colleagues found (Clinical Interventions in Aging, 2014).
One groundbreaking study showed that brighter fluorescent lights in common areas in nursing homes had a positive effect on cognitive function in Alzheimer's patients in managed-care settings, as well as lessening symptoms of depression, compared with residents who received less light (JAMAopens in new window, 2008). Another study by Figueiro and colleagues that tested bright overhead lighting for people with dementia living at home also found that the intervention reduced symptoms of depression in patients, and helped them sleep more regularly and efficiently (Sleep Health, in press).
"I have no question that if you deliver the right light in Alzheimer's patients you will improve their behavior; you will improve agitation; they will sleep better," says Figueiro. "The results are very robust."
She has also developed a 24-hour lighting schemeopens in new window for older adults for the American Institute of Architects. Its strategies include the use of bright table lamps by day and dimmer, yellowish white illuminated door frames at night that can help reduce falls.
Adolescents and sleep
Adolescents are particularly sensitive to light-dark cycles. Beginning in early puberty, melatonin levels in the body start to peak later and later at night, significantly pushing back the time when adolescents feel sleepy. Because most teens need to wake up early for school, those late nights significantly decrease their total sleep time, which can lead to a number of issues including worse academic performance in school and mood problems. Delayed sleep times are also associated with seasonal affective disorder, which can affect teens as well as adults.
Teens' nighttime use of brightly lit computers and smartphones can make it even harder for them to fall asleep. In her research, Figueiro found that computers and laptops suppressed melatonin in 15- to 17-year-olds more than in the general population. Even one hour in front of a screen decreased melatonin levels by 23 percent (Lighting and Research Technologyopens in new window, 2015).
Come morning, adolescents may face more circadian challenges if they lack enough bright light to start their days. In some seasons, children are in school before the sun rises, so they miss out on the morning daylight. That could affect their sleep later that night, suggests a 2010 study by Figueiro and her Rensselaer colleague Mark Rea, PhD. They found that teens whose intake of bright light was artificially dimmed during the morning with blue-light blocking glasses took longer to fall asleep at night (Neuro Endocrinology Letters, 2010).
Yet those same glasses could prove useful in the evening. In a study of 13 students ages 15 to 17, Stephanie van der Lely of the University of Basel and colleagues found that blue-light blocking glasses decreased screen-induced melatonin suppression and led to self-reported increase in sleepiness compared with a control group that did not wear glasses (Journal of Adolescent Health,opens in new window 2015).
Another study found that a dose of bright white light at home in the morning may give adolescents a boost to better handle the day ahead. Figueiro and Rea exposed 18 sleep-restricted adolescents ages 12 to 17 to 80 minutes of short-wavelength light after the teens woke. The teens' saliva samples showed that the light increased levels of the energy boosting hormone cortisol compared with when they were exposed to dim light (International Journal of Endocrinologyopens in new window, 2012).
Waking to a simulator that gradually brightened a room — much like the rising sun — also showed benefits, improving teens' performance on cognitive tests, according to a study of 56 teenagers by psychologist Lorenzo Tonetti, PhD, of the University of Bologna and colleagues (European Journal of Applied Physiologyopens in new window, 2015). The tool should appeal to parents and educators, Tonetti says, because within a relatively short time — 20 minutes each day over two weeks — the inexpensive simulator had a positive alerting effect, though future research should investigate whether either a prolonged or cyclical use of the device is even more effective.
Night shifts
The 15 million people who work at night in the United States face even more serious issues due to circadian misalignment. Humans evolved to be awake during the day, but many night shift workers must sleep days and stay up nights. Long-term, that disruption can have many health consequences. As psychologist Charmane Eastman, PhD, and Mark R. Smith, PhD, of Rush University Medical Center, wrote in a 2012 review for Nature and Science of Sleepopens in new window, shift workers are at a greater risk for cardiovascular disease, being overweight and reproductive problems. The International Agency for Research on Cancer recently classified shift work as a "probable carcinogen." A relative lack of melatonin, a natural antioxidant, may be one mechanism that explains shift workers' increased risk of cancer, according to the review.
While stimulants, sedatives and melatonin supplements can induce alertness or sleep in night workers in the short term, the best way to reduce the health risks may be to enforce a full circadian shift with a longer-term light-dark plan that includes black-out curtains and masks for sleeping and at least one hour of electric bright light while working, Eastman's review says. In addition, blue-light blocking sunglasses during a daytime drive home from work helps prevent waking signals from daylight. And employees should avoid changing shift schedules too frequently — such as working 7 a.m. to 7 p.m. one day and 7 p.m. to 7 a.m. the next. A three-shift system that gradually delays sleep times — such as two weeks of days, two weeks of evenings, then two of night — gives the body time to adapt.
Though the research is promising, more is needed to better understand lighting's effects on our mental and physical health and what treatments may help. In particular, the field needs more multidisciplinary collaboration to span physiology, psychology, lighting technology and architecture, says Veitch of Canada's National Research Council. "It's a really good example of how psychology needs to have a place at the STEM table," she says.
