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Comparisons of three practical field devices used to measure personal light exposures and activity levelsLighting Research & Technology - MG Figueiro, R Hamner, A Bierman, MS Rea, 2013

This paper documents the spectral and spatial performance characteristics of two new versions of the Daysimeter, devices developed and calibrated by the Lighting Research Center to measure and record personal circadian light exposure and activity levels, and compares them to those of the Actiwatch Spectrum. Photometric errors from the Daysimeters and the Actiwatch Spectrum were also determined for various types of light sources. The Daysimeters had better photometric performance than the Actiwatch Spectrum. To assess differences associated with measuring light and activity levels at different locations on the body, older adults wore four Daysimeters and an Actiwatch Spectrum for seven consecutive days. Wearing the Daysimeter or Actiwatch Spectrum on the wrist compromises accurate light measurements relative to locating a calibrated photosensor at the plane of the cornea.

Effects of exercise with or without light exposure on sleep quality and hormone reponses

Cycling adenosine monophosphate (cAMP) gets released by the stimulus of adrenocortical hormones due to intake of coffee, tea, chocolate, or stress. Excessive cAMP release accelerates energy release to reach excitement condition that leads us to be nervous and unsettled. However, sunlight exposure decreases cAMP, leading to peaceful and settled conditions [53].

10x risk of death from non-skin cancer due to low sun exposure

Many studies have shown that cancer-related death rates decline as one moves toward the lower latitudes (between 37°N and 37°S), and that the levels of ambient UVR in different municipalities correlate inversely with cancer death rates there. “As you head from north to south, you may find perhaps two or three extra deaths [per hundred thousand people] from skin cancer,” says Vieth. “At the same time, though, you’ll find thirty or forty fewer deaths for the other major cancers. So when you estimate the number of deaths likely to be attributable to UV light or vitamin D, it does is not appear to be the best policy to advise people to simply keep out of the sun just to prevent skin cancer.”

Lower risk of high blood pressure with sunlight

exposed a group of hypertensive adults to a tanning bed that emitted full-spectrum UVR similar to summer sunlight. Another group of hypertensive adults was exposed to a tanning bed that emitted UVA-only radiation similar to winter sunlight. After three months, those who used the full-spectrum tanning bed had an average 180% increase in their 25(OH)D levels and an average 6 mm Hg decrease in their systolic and diastolic blood pressures, bringing them into the normal range. In constrast, the group that used the UVA-only tanning bed showed no change in either 25(OH)D or blood pressure.

Low vitamin D = 4-5X increase in risk of type 1 diabetes

A Swedish epidemiologic study published in the December 2006 issue of Diabetologia found that sufficient vitamin D status in early life was associated with a lower risk of developing type 1 diabetes. Nonobese mice of a strain predisposed to develop type 1 diabetes showed an 80% reduced risk of developing the disease when they received a daily dietary dose of 1,25(OH)D, according to research published in the June 1994 issue of the same journal. And a Finnish study published 3 November 2001 in The Lancet showed that children who received 2,000 IU vitamin D per day from 1 year of age on had an 80% decreased risk of developing type 1 diabetes later in life, whereas children who were vitamin D deficient had a fourfold increased risk. Researchers are now seeking to understand how much UVR/vitamin D is needed to lower the risk of diabetes and whether this is a factor only in high-risk groups.

North of 37 degrees double MS risk

living at a latitude above 37° increased the risk of developing MS throughout life by greater than 100%.

Melanoma away from sun exposure

Moreover, although excessive sun exposure is an established risk factor for cutaneous malignant melanoma, continued high sun exposure was linked with increased survival rates in patients with early-stage melanoma in a study reported by Marianne Berwick, an epidemiology professor at the University of New Mexico, in the February 2005 Journal of the National Cancer Institute. Holick also points out that most melanomas occur on the least sun-exposed areas of the body, and occupational exposure to sunlight actually reduced melanoma risk in a study reported in the June 2003 Journal of Investigative Dermatology.

Lower rates of some cancers with vitamin D

Whereas skin cancer is associated with too much UVR exposure, other cancers could result from too little. Living at higher latitudes increases the risk of dying from Hodgkin lymphoma, as well as breast, ovarian, colon, pancreatic, prostate, and other cancers, as compared with living at lower latitudes. A randomized clinical trial by Joan Lappe, a medical professor at Creighton University, and colleagues, published in the June 2007 issue of the American Journal of Clinical Nutrition, confirmed that taking 2–4 times the daily dietary reference intake of 200–600 IU vitamin D3 and calcium resulted in a 50–77% reduction in expected incidence rates of all cancers combined over a four-year period in post-menopausal women living in Nebraska.

Sun reduces TB

a meta-analysis published in the February 2008 International Journal of Epidemiology found that high vitamin D levels reduce the risk of active TB (i.e., TB showing clinical symptoms) by 32%.

White skin an evolutionary adaption for low sunlight in north latitudes?

In the July 2000 issue of the Journal of Human Evolution, California Academy of Sciences anthropologists Nina Jablonski and George Chaplin wrote that because dark skin requires about five to six times more solar exposure than pale skin for equivalent vitamin D photosynthesis, and because the intensity of UVB radiation declines with increasing latitude, one could surmise that skin lightening was an evolutionary adaptation that allowed for optimal survival in low-UVR climes, assuming a traditional diet and outdoor lifestyle.

Smarter in the sun?

Besides suppressing melatonin and warding off any residual sleepiness, recent studies suggest that bright light acts as a stimulant to the brain. Gilles Vandewalle and colleagues at the University of Liège in Belgium asked volunteers to perform various tasks in a brain scanner while exposing them to pulses of bright white light or no light. After exposure to white light, the brain was in a more active state in those areas that were involved in the task. Although they didn’t measure the volunteers’ test performances directly, if you are able to recruit a greater brain response, then your performance is likely to be better: you will be faster or more accurate, Vandewalle says.

Is the dark really making me sad? | Ars Technica

Since October 2015, Anna’s classroom has been fitted with ceiling lights that change in colour and intensity to simulate being outside on a bright day in springtime. Developed by a company called BrainLit, the ultimate goal is to create a system that is tailored to the individual, monitoring the type of light they’ve been exposed to through the course of a day and then adjusting the lights to optimise their health and productivity.

Is the dark really making me sad? | Ars Technica

the leading theory is the ‘phase-shift hypothesis’: the idea that shortened days cause the timing of our circadian rhythms to fall out of sync with the actual time of day, because of a delay in the release of melatonin. Levels of this hormone usually rise at night in response to darkness, helping us to feel sleepy, and are suppressed by the bright light of morning. “If someone’s biological clock is running slow and that melatonin rhythm hasn’t fallen, then their clock is telling them to keep on sleeping even though their alarm may be going off and life is demanding that they wake up,” says Kelly Rohan, a professor of psychology at the University of Vermont. Precisely why this should trigger feelings of depression is still unclear. One idea is that this tiredness could then have unhealthy knock-on effects. If you’re having negative thoughts about how tired you are, this could trigger a sad mood, loss of interest in food, and other symptoms that could cascade on top of that. However, recent insights into how birds and small mammals respond to changes in day length have prompted an alternative explanation. According to Daniel Kripke, an emeritus professor of psychiatry at the University of California, San Diego, when melatonin strikes a region of the brain called the hypothalamus, this alters the synthesis of another hormone—active thyroid hormone—that regulates all sorts of behaviours and bodily processes. When dawn comes later in the winter, the end of melatonin secretion drifts later, says Kripke. From animal studies, it appears that high melatonin levels just after the time an animal wakes up strongly suppress the making of active thyroid hormone—and lowering thyroid levels in the brain can cause changes in mood, appetite, and energy. For instance, thyroid hormone is known to influence serotonin, a neurotransmitter that regulates mood. Several studies have shown that levels of brain serotonin in humans are at their lowest in the winter and highest in the summer. In 2016, scientists in Canada discovered that people with severe SAD show greater seasonal changes in a protein that terminates the action of serotonin than others with no or less severe symptoms, suggesting that the condition and the neurotransmitter are linked.

Is the dark really making me sad? | Ars Technica

Seasonality is reported by approximately 10 to 20 percent of people with depression and 15 to 22 percent of those with bipolar disorder. “People often don’t realise that there is a continuum between the winter blues—which is a milder form of feeling down, [sleepier and less energetic]—and when this is combined with a major depression,” says Anna Wirz-Justice, an emeritus professor of psychiatric neurobiology at the Centre for Chronobiology in Basel, Switzerland. Even healthy people who have no seasonal problems seem to experience this low-amplitude change over the year, with worse mood and energy during autumn and winter and an improvement in spring and summer, she says.

Is the dark really making me sad? | Ars Technica

And in his Treatise on Insanity, published in 1806, the French physician Philippe Pinel noted a mental deterioration in some of his psychiatric patients “when the cold weather of December and January set in."

Vitamin D Speeds Recovery From Tuberculosis, Scientists Report - The New York Times

In a clinical trial of 95 patients on antibiotics, those who also got vitamin D had less inflammation, and the mycobacteria in their lung phlegm cleared up 13 days earlier on average.

ADjusting the body's clock with light to counter depression

Researchers have developed a limited form of sleep deprivation that is euphemistically called wake therapy. It has been shown to have sustained antidepressant benefit in patients with bipolar disorder and major depression. The idea is to get up for the day halfway through the usual sleep period, which shifts the circadian clock to an earlier time. It’s thought that this works by realigning the sleep cycle with other circadian rhythms, like changes in levels of body temperature and the stress hormone cortisol, that are also out of sync with each other in depression. Studies show that it is possible to make wake therapy even more powerful by incorporating two additional interventions: early morning light therapy and what’s called sleep phase advance, in which the patient goes to bed about five to six hours earlier than usual and sleeps for about seven hours. This combination of treatments is called triple chronotherapy, and the typical course involves one night of complete sleep deprivation followed by three nights of phase-advanced sleep and early morning light. In one study of 60 hospitalized patients with bipolar depression who were taking antidepressants or lithium, 70 percent of those who did not have a history of drug resistance improved rapidly with sleep deprivation and early morning light, and 57 percent remained well after nine months. Encouragingly, 44 percent of patients who had failed to respond to at least one trial of anti-depressants also improved.

Gene mutation helps explain night owl behavior

Night owls are often diagnosed at sleep clinics with delayed sleep phase disorder (DSPD). This study is the first to implicate a gene mutation in the development of DSPD, which affects up to 10% of the public, according to clinical studies. People with DSPD often struggle to fall asleep at night, and sometimes sleep comes so late that it fractures into a series of long naps. DSPD and other sleep disorders are associated with anxiety, depression, cardiovascular disease, and diabetes. People with DSPD also have trouble conforming to societal expectations and morning work schedules. "It's as if these people have perpetual jet lag, moving eastward every day," says Young. "In the morning, they're not ready for the next day to arrive." Patke is a night owl and usually works late into the night. She, however, does not carry the CRY1 variant. Not all cases of DSPD are attributable to this gene mutation. However, Young and Patke found it in 1 in 75 of individuals of non-Finnish, European ancestry in a gene database search. "Our variant has an effect on a large fraction of the population," she says. Young, who has studied the genes involved in the circadian clock of the fruit fly, connected with clinical researchers at the Weill Cornell Medical College to understand the molecular underpinnings of human sleep disorders. By studying the skin cells of people with DSPD, he and Patke discovered a mutation in CRY1, which helps drive the circadian clock. The circadian clock is a fundamental element of life on Earth and has remained more or less the same, genetically, throughout the evolution of animals. "It's basically the same clock from flies to humans," Young says. Normally the clock begins its cycle by building up proteins, call activators, in a cell. These activators produce their own inhibitors that, over time, cause the activators to lose their potency. When all the activators in the cell have been silenced, inhibitors are no longer produced and eventually degrade. Once they've all gone, the potency of the activators surges, and the cycle begins again. The CRY1 protein is one of the clock's inhibitors. The mutation Young and Patke found is a single-point mutation in the CRY1 gene, meaning just one letter in its genetic instructions is incorrect. Yet this change causes a chunk of the gene's resulting protein to be missing. That alteration causes the inhibitor to be overly active, prolonging the time that the activators are suppressed and stretching the daily cycle by half an hour or more. In addition to their initial study of a multigenerational family in the U.S., Young and Patke collaborated with clinical researchers at Bilkent University to analyze the sleep patterns of six families of Turkish individuals, 39 carriers of the CRY1 variant and 31 non-carriers. The carriers had delayed sleep onset times and some had fractured, irregular sleep patterns. The mid-point of sleep for non-carriers was about 4 a. m. But for carriers, the mid-point was shifted to 6-8 a.m. Because the mutation does not disable the protein, it can have an effect on individuals whether they carry one or two copies of the gene. Of the 39 Turkish carriers studied, 8 had inherited the mutation from both parents, and 31 had inherited only one copy of the mutation. The circadian clock responds to external environmental cues, so it is possible for people to manage the effects of the mutation on sleep. For instance, one carrier in the study reported maintaining a sleep routine through self-enforced regular sleep and wake times and exposure to bright light during the day. "An external cycle and good sleep hygiene can help force a slow-running clock to accommodate a 24-hour day," says Patke. "We just have to work harder at it."

Light boosts serotonin

Exposure to bright light is a second possible approach to increasing serotonin without drugs. Bright light is, of course, a standard treatment for seasonal depression, but a few studies also suggest that it is an effective treatment for nonseasonal depression38 and also reduces depressed mood in women with premenstrual dysphoric disorder39 and in pregnant women suffering from depression.40 The evidence relating these effects to serotonin is indirect. In human postmortem brain, serotonin levels are higher in those who died in summer than in those who died in winter.41 A similar conclusion came from a study on healthy volunteers, in which serotonin synthesis was assessed by measurements of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the venous outflow from the brain.42 There was also a positive correlation between serotonin synthesis and the hours of sunlight on the day the measurements were made, independent of season. In rats, serotonin is highest during the light part of the light–dark cycle, and this state is driven by the photic cycle rather than the circadian rhythm.43,44 The existence of a retinoraphe tract may help explain why, in experimental animals, neuronal firing rates, c-fos expression and the serotonin content in the raphe nuclei are responsive to retinal light exposure.44–48 In humans, there is certainly an interaction between bright light and the serotonin system. The mood-lowering effect of acute tryptophan depletion in healthy women is completely blocked by carrying out the study in bright light (3000 lux) instead of dim light.49

Is the surge in type 2 diabetes related to indoor life (video games + NFL)

Specialists from the University of Geneva (UNIGE) and the University Hospitals of Geneva (HUG) studied pancreatic ɑ- and β- cells that are in charge of the production of insulin and glucagon, two hormones that regulate glucose levels in the blood. They discovered that already at cellular levels, these internal clocks orchestrate the timing of proper hormone secretion, thus optimizing body metabolism by anticipating the rest-activity and feeding-fasting cycles. Their misalignment would thus favor the occurrence of metabolic diseases. Their discovery, to be read in the journal Genes and Development, highlights an essential factor, yet still poorly understood, which may explain diabetes development as a consequence of circadian misalignments of these cellular clocks. With type 2 diabetes affecting younger and younger people in the western world, researchers work on understanding how lifestyle changes in recent decades contribute to this ever-expanding epidemic, in the view of finding news strategies to curb it.

Tanning dependence linked to other addictive behaviors, new study finds -- ScienceDaily

The connections between tanning dependence and other disorders revealed by the study represent an opportunity for clinicians to address those related conditions. "People who are tanning dependent could also be assessed for SAD," said Cartmel. "There are ways of addressing SAD other than indoor tanning. Regarding the alcohol dependence association, it may be possible that addressing that behavior could help address tanning dependence." The underlying mechanisms for the addiction to UV light are not yet fully understood. According to other studies, "The biological rationale for tanning dependence is that exposure to UV light results in both melanin, and endorphin production," said Cartmel. She also added that there was another interesting preliminary finding: those with tanning dependence were five times more likely to exhibit "exercise addiction." She said it is too early, however, to determine the implication. "Exercise addiction" itself has really not been well researched," she said. "One hypothesis behind the finding is that people who exercise excessively do so because they are very aware of their appearance, and they also feel that being tanned improves their appearance. Or it may be that we will eventually find out that these individuals have more of an addictive or risk-taking personality type. If you have one type of dependence, you may be more likely to have another addiction," Cartmel said.

Scientists identify brain circuit that drives pleasure-inducing behavior: Surprisingly, the neurons are located in a brain region thought to be linked with fear -- ScienceDaily

The researchers found that five of these populations stimulate reward-related behavior: When the mice were exposed to light, the mice repeatedly sought more light exposure because these neurons were driving a reward circuit. These same populations all receive input from the positive emotion cells in the BLA.

Cellular jetlag seems to favor the development of diabetes -- ScienceDaily

studied pancreatic ɑ- and β- cells that are in charge of the production of insulin and glucagon, two hormones that regulate glucose levels in the blood. They discovered that already at cellular levels, these internal clocks orchestrate the timing of proper hormone secretion, thus optimizing body metabolism by anticipating the rest-activity and feeding-fasting cycles. Their misalignment would thus favor the occurrence of metabolic diseases. Their discovery, to be read in the journal Genes and Development, highlights an essential factor, yet still poorly understood, which may explain diabetes development as a consequence of circadian misalignments of these cellular clocks.

More than half of college football athletes have inadequate levels of vitamin D: Vitamin D deficiency linked to muscle injuries -- ScienceDaily

The study, presented at the American Academy of Orthopaedic Surgeons Annual Meeting on March 16, included 214 college athletes who took part in the 2015 combine. Baseline data was collected, including age, body mass index (BMI), injury history, and whether they had missed any games due to a lower extremity muscle strain or core muscle injury. The average age of the athletes was 22. Their vitamin D levels were determined with a blood test. Levels were defined as normal (? 32 ng/mL), insufficient (20 -- 31 ng/mL), and deficient (< 20 ng/mL). A total of 126 players (59%) were found to have an abnormal serum vitamin D level, including 22 athletes (10%) with a severe deficiency. Researchers found a significantly higher prevalence of lower extremity muscle strain and core muscle injury in those who had low vitamin D levels. Fourteen study participants reported missing at least one game due to a strain injury, and 86% of those players were found to have inadequate vitamin D levels.

For Better Vision, Let the Sunshine In - The New York Times

Strong correlations were found between current eyesight and volunteers’ lifetime exposure to sunlight, above all UVB radiation (which is responsible for burning). Those who had gotten the most sun, particularly between the ages of 14 and 19, were about 25 percent less likely to have developed myopia by middle age. Exposure to sunlight up to the age of 30 also conferred a protective benefit.