Bright Light Exposure Improves Your Workouts Sign. (~8%)

Would be interesting to compare sunlight and artificial light in future studies.

You will remember the circadian rhythm series in which I have previously discussed the relevance of light exposure as a means to set, reset and entrain your internal clock in order to reap all sorts of health and performance benefits.

Bright (>4000 lux), preferable blue (at least having a blue component) light has repeatedly been shown to increase athletic performance. Studies like Kantermann et al. (2012) show, however, that the efficacy of bright light exposure significantly depends on the chronotype of an athlete.

Learn more about the health effects of correct / messed up circadian rhythms

Sunlight, Bluelight, Backlight and Your Clock

Sunlight a La Carte: "Hack" Your Rhythm

Breaking the Fast to Synchronize the Clock

Fasting (Re-)Sets the Peripheral Clock

Vitamin A & Caffeine Set the Clock

Pre-Workout Supps Could Ruin Your Sleep

In said study, the athletes were exposed to 4420 lux for 120 min before and right before a 40-min time trial. Significant performance increases were observed only for those subjects, though, who were performing ∼14.8 h after their midpoint of sleep on free days (MSFsc). Subjects who trained "earlier" on their internal clock (in this case ∼11.8 h after the MSFsc), on the other hand, did not record any benefits.

Back in the day, Kantermann et al. speculated that a short(er) exposure or mudaltion of light intensity and/or timing could likewise have affected their results. Thus, the hypothesis Knaier et al. used in their 2015 contribution to the "light for performance" research was to that different bright light (BL) exposure regimes prior to and during a time-trial applied during the “sensitive” phase of the circadian rhythm result in a dose dependent increase of time-trial power output - meaning: longer exposure and brighter light = maximal performance benefits.

To test this hypothesis the scientists assigned young (25.1 ± 3.1 years) men to three groups with two different light intensities (A = BL, 4420 lx vs. B = ML, 230 lx) for all three randomly chosen exposure times (2h pre + exercise time, 2HEX | 1h pre + exercise time 1HEX | 1h pre 1H).

Figure 1: Study protocol for 2HEX, 1HEX, and 1H. Time-trial: 40 min in duration; bright light/moderate light (BL/ML): continuous randomized exposure (slightly rearranged version of a figurr from Knaier. 2015).

As Figure 1 illustrates we are thus dealing with a total of three trials and their moderate light counter parts which are not illustrated in Figure 1. Thanks to the use of a cross-over design this means that all subjects were exposed to either bright light (BL, 4420 lux) or moderate light (ML, 230 lx).

Figure 2: Total work (in kJ) during the 40-minute time-trial to exhaustion (Knaier. 2015).

The scientists' analyses of the studies results and the normalization of the results according to the subjects' individual chronotype (estimated based on the Munich Chronotype Questionnaire) yielded the following two primary study outcomes:

• Total work performed during the time-trial in kJ in the 2HEX group was significantly higher in the BL setting (527 kJ) than in ML (512 kJ) (P = 0.002), but not in 1HEX (BL: 485 kJ; ML: 498 kJ) or 1H (BL: 519 kJ; ML: 514 kJ) (P = 0.770; P = 0.485). 
• There was a significant (P = 0.006) positive dose–response relationship between the duration of light exposure and the work performed over the three doses of light exposure. 

Overall, the study does therefore confirm that "[a] long duration light exposure is an effective tool to increase total work in a medium length timetrial" - what's new (compared to the previously referenced Kantermann study is the observation that this advantage holds, even if the results are normalized for the subjects' individual chronotype.

Whether and to which extent the "more light equals more performance" equation will hold with (a) even longer or (b) even more intense light, however, is something that will have to be investigated in future dose-response studies. Studies like O'Brien et al. (2000) which has already proven that shortening the exposure time (in this case to 20 minutes only during exercise) will reduce the effects of bright light exposure on cycling performance to zero.

Bottom line: While one hour of bright or 2h of medium intensity light appears to allow for too little 'light accumulation' to have physiologically relevant affects, long duration of exposure to bright light is, as Knaier et al. point out "an effective tool to increase total work at least for the initial phase of a medium length time-trial" (Knaier. 2015); and what's important, the performance increase of ~8% which was observed not just in the Knaier study, but also in a differently designed trial by Thomson, et al. (2015 | cf. Figure 3), is large enough to be relevant for any competing athlete.

Figure 3: A study by Thompson, et al. (2015) suggests that pre-bed exposition to bright light (30 min) can increase the time-trial performance of athletes on the subsequent morning. Since this will also suppress the melatonin levels of practitioners this is yet a strategy that should not be employed regular (competition only).

The results of Knaier are thus in contrast to a similarly recent study by Nelson et al. (2015) who found that acute short-term dim light exposure can actually lower muscle strength endurance (-18%, albeit with high inter-individual variability). Against that background it should be obvious that, even though, bright light exposure is indeed "likely to increase alertness and reduce sleepiness and help athletes to compensate for disadvantages in competitions at unfavorable times and improve performance" (Knaier. 2015). And don't forget - the scientists from the University of Basel are right: "The ideal duration of expo sure to increase performance and simultaneously interfere as little as possible with athletes’ routine still needs to be found" (Knaier. 2015). In fact, even timing and strategies like the pre-evening light exposure that increased the time trial performance in Thomson et al. (2015 | see Figure 3) must be tested as alternatives | Comment on Facebook!

References:

• Kantermann, Thomas, et al. "The stimulating effect of bright light on physical performance depends on internal time." PloS one 7.7 (2012): e40655.
• Knaier, R., et al. "Dose–response relationship between light exposure and cycling performance." Scandinavian journal of medicine & science in sports (2015).
• Nelson, Arnold G., Joke Kokkonen, and Megan Mickenberg. "Acute short-term dim light exposure can lower muscle strength endurance." Journal of Sport and Health Science 4.3 (2015): 270-274.
• O'Brien, Patrick M., and Patrick J. O'Conner. "Effect of bright light on cycling performance." Medicine & Science in Sports & Exercise (2000).
• Thompson, A., et al. "The effects of evening bright light exposure on subsequent morning exercise performance." International journal of sports medicine 36.02 (2015): 101-106.

Let There Be Light: 10 New Studies to Enlighten You About the Health Effects of Light Exposure on Health & Physique

No, the sun does not kill you. If you control your exposure it may extend your life and improve your life-quality significantly.

It's about time to "let there be light" to illuminate the benefits of regular well-timed exposure to sunlight and it's short frequency component. Only recently, researchers from the Japanese National Institute of Advanced Industrial Science and Technology (AIST) were able to show that daytime light exposure has significant beneficial effects on cognitive brain activity. Significant enough to have the subjects perform better on an oddball task and to significantly increase cortical activity related to cognitive processes (Okamoto. 2014).

But is that really all, bright light, or more specifically, the regular and well-timed exposure to bright light can do for you?

The effects on circadian rhythm could be behind the Sun's anti-cancer effects

Sunlight, Bluelight, Backlight and Your Clock

Sunlight a La Carte: "Hack" Your Rhythm

Breaking the Fast to Synchronize the Clock

Fasting (Re-)Sets the Peripheral Clock

Vitamin A & Caffeine Set the Clock

Pre-Workout Supps Could Ruin Your Sleep

Certainly not. I mean if it's ill-timed, like the evening use of light-emitting eReaders it will negatively affect your sleep, mess up your circadian rhythm and decrease your alertness on the next morning. Similar results, i.e. drowsiness and suppression of energy metabolism the following morning, have been reported by other studies, as well (Kayaba. 2014).

As a SuppVersity reader you do yet know all about those negative effects from the circadian rhythm series, anyway. Reason enough for me, to focus primarily on all the good stuff, the well-timed exposure to bright light can do for you in today's Special of the SuppVersity Short News.

• If you can't let go off your mobile at night, use blue blocker glasses as a countermeasure for alerting effects of evening light-emitting diode screen exposure - According to researchers from the Psychiatric Hospital of the University of Basel, blue blocker glasses (BB) significantly attenuate LED-induced melatonin suppression in the evening and decrease vigilant attention and subjective alertness before bedtime.
  
  Strangely, though, visually scored sleep stages and behavioral measures collected the morning after were not modified. Still, van der Lely et al. conclude: "BB glasses may be useful in adolescents as a countermeasure for alerting effects induced by light exposure through LED screens and therefore potentially impede the negative effects modern lighting imposes on circadian physiology in the evening "(van der Lely. 2014).
• UV-light protects against "brainflammation" in MS model - Scientists from the University of Wisconsin-Madison report in their latest paper that UV light selectively inhibits spinal cord inflammation and demyelination in experimental autoimmune encephalomyelitis.
  
  Previous studies have already shown that UV radiation (UVR) can suppress experimental autoimmune encephalomyelitis (EAE), an animal model of multiple-sclerosis (MS), independent of vitamin D production. The mechanism of this suppression did yet remain to be elucidated, until Wang et al. (2014) observed that UVR (10kJ/m²) does not just inhibit the inflammation and demyelination of the spinal cord, but will also dramatically and significantly reduce spinal cord chemokine CCL5 mRNA and protein levels.
  
  In conjunction with an increased production of intereron-gamma (IFN-γ) and IL-10, which are actually used to treat all sorts of autoimmune diseases, artificial and natural UV light can thus actually "prevent the migration of inflammatory cells into the CNS" (Wang. 2014).

• 

  Melatonin conc. after 4 days w/ dim vs. bright light and tryptophan rich vs. poor breakfast (Fukushige. 2014).

  Bright light in the AM and the consumption of a breakfast that's high in tryptophan can help you maintain a healthy circadian rhythm - In case you are asking yourself how you can grasp all the benefits that are associated with having an intact circadian rhythm, you may be intrigued to hear that researchers from the Fukuoka Women's University have been able to show that an increase in tryptophan intake at breakfast combined with daytime light exposure has beneficial effects on melatonin secretion and sleep quality. As you can see in the figure to the left it will significantly elevate the evening melatonin peak, which is critical for an optimal circadian rhythm.
  
  If you are looking to optimize your internal clock bright light (either sunlight or a 10,000 Lux daylight lamp) + tryptophan (seeds, nuts, soy, cheese, chicken, turkey, fish, oats, beans and eggs are the TOP10 sources) are the way to go. If you want an extra "kick" add some coffee to the equation. This will increase the light responsiveness of the circadian pacemaker - well, at least in mice it does (Diepen. 2014).

If you want to design your own "dawn simulator" that's the spectrum you need (Virginie. 2014).

Wanna be smarter, but can't get enough sleep? Start your day with a dawn simulation: Chronic sleep restriction (SR) has deleterious effects on cognitive performance that can be counteracted by light exposure. Scientists from the Psychiatric Hospital of the University of Basel have recently been able tho show that a dawn simulating in the AM will increase your task performance throughout the day after morning; and what's best: The benefit was most pronounced in those participants who sucked the most when they didn't get a good night's sleep (Virginie. 2014).

• Bright lights at work will keep you sane, happy and alert - If you are working in an insufficiently lit office without natural sunlight, you should be prepared to develop physiological, sleep and depressive symptoms.
  
  Assuming you have a window in your office, you will get a significantly more pronounced total and peak exposure to bright light that's going to correlate with 33% reduced levels of the stress hormone cortisol, a more natural rhythm of melatonin and a reduced risk of minor psychiatric disorders and depressive symptoms (MA) in the evening.
  
  That's at least what the results of a recent study from the UFRGS in Porto Alegre indicates (Harb. 2014). A study the authors of which proudly say that their "study demonstrated that not only may light pollution affect human physiology but also lack of exposure to natural light is related to high levels of cortisol and lower levels of melatonin at night, and these, in turn, are related to depressive symptoms and poor quality of sleep" (Harb. 2014).

• 

  If you want to light up the darkness, when it's actually time to sleep do it with green (555nm) or red, not blue light, which suppresses melatonin (Bonmati-Carrion. 2014).

  Staying away from nightly night exposure may also help to keep your arteries clean even in the old age - Studies indicate that even after  adjustment for confounding factors, including age, gender, body mass index, current smoking status, hypertension, diabetes, dyslipidemia, sleep medication, estimated glomerular filtration rate, nocturia, bedtime, duration in bed (scotoperiod), day length (photoperiod), urinary 6-sulfatoxymelatonin excretion and daytime and nighttime physical activity, exposure to light at night is associated with carotid intima-media thickness (Obayashi. 2014).
  
  If you don't want to develop subclinical carotid atherosclerosis, when you are old, it would thus be a good idea to adhere to the basic rules of sleep hygiene: a dark room and/or blindfolds will keep your arteries clean and may thus save your life ;-)
• If you have kidney problems, get out in the sun if you want to survive - Scientists from the University of California Irvine Medical Center were able to show that dialysis patients residing in higher UV index regions have lower all-cause mortality compared to those living in moderate-high UV regions (Shapiro. 2014).
  
  More specifically, the ~60year-old subjects residing in moderate-high UV index regions had a 16% reduced risk of all-cause mortality. Those living in very-high UV index regions had a 1% higher risk reduction (17%). Interestingly, there was a similar inverse association between UV index and mortality was observed across all subgroups, but it was more pronounced among whites vs. non-whites.
• Wear those shades (or bluelight blocker glasses) before any important sport event - Why? Stupid question. If you dabble around with your smartphone "unprotected" the evening before an important sport event for only 30 minutes, this can influence exercise performance under hot conditions during the subsequent early morning (Thompson. 2014).

Even brief light exposure, when your eyes are closed messes with your circadian rhythm.

Pah, when your eyes are closed, light is not a problem, right? Wrong. Even ,illisecond flashes of light phase delay the human circadian clock during sleep. While a greater number of matched subjects and more research will be necessary to ascertain whether these light flashes affect sleep, data from a recent study from the California Mental Illness Research Education and Clinical Center suggest that 2-msec light flashes given every 30 sec have an effect on the circadian rhythm of healthy volunteers. And while Zeitzer et al. (2014) tried to use the flashes to modify the rhythm in a beneficial way, the exact opposite can also be the case. It all depends on how / when you are exposed to light when you sleep.

Sleep disturbance and adaptive immunity. Following a night of sleep loss, or during a period of sleep disturbance, nerve fibers from the sympathetic nervous system (SNS) release the neurotransmitter norepinephrine into primary and secondary lymphoid organs and stimulate the adrenal gland to release stored epinephrine into systemic circulation. Both neuromediators stimulate leukocyte adrenergic receptors (e.g., ADRB2) and activate nuclear factor (NF)-κB-mediated inflammatory programs (Irwin. 2015).

• If your grandparent's have Alzheimer's install a timer-based light system - This may not just increase their sleep quality, but it will also improve their behavior and mood as indicated by reduced depression scores on the Cornell Scale for Depression in Dementia and agitation scores from the Cohen-Mansfield Agitation Inventory (Figueiro. 2014).
  
  I must warn you, though: The recent field study from the Rensselaer Polytechnic Institute is promising, but the results should be replicated using a larger sample size and perhaps using longer treatment duration.
• If you have to work night shifts consider using 1-5mg melatonin 1h before you go to bed - Why? You have to counter the natural decline in melatonin production that occurs over consecutive days of night work (Dumont. 2014).
  
  In a recent study from the Sacre-Coeur Hospital of Montreal the melatonin production of the healthy volunteers decreased progressively decreased over consecutive days of simulated night work, both during nighttime and over the 24 h. Interestingly, this decrease was larger in women using oral contraceptives and independent of bright light exposure.
• Get out into the sun and cure your back pain - If your back hurts and neither you or your doctor have a clue why, try getting into the sun. A study from the UMIT in Austria shows that only three sessions in front of 5.000 lx lamp improved the depressive symptoms and reduced the pain intensity in CNBP adults with chronic nonspecific back pain (Leichtfried. 2014).

One of the side effects of blue light LED exposure (open circles) in the PM is a sign., but practically prob. irrelevant reduction in energy exp. on the next morning (Kayaba. 2014).

Bottom line: I really hope that I do not have to sum up the results for you. I mean, it should be obvious that sleep hygiene at night and light exposure at day are among the most important factors of the lifestyle-factors in the exercise + nutriton + lifestyle solution to perfect health & obesity protection (Partonen. 2014).

Against that background I would like to use the last lines to put another emphasis on the results of the recent study by Kayaba et al. (2014) which found that one of the negative consequences smartphone junkies have to suffer on the morning after using their devices before bed is a reduction in energy expenditure.

If you take a look at the data in the figure at the right (open circles = exposed; full circles = non-exposed), you will yet realize that this probably isn't the worst side effect of blue-LED light exposure in the evening. The reduction is significant in the AM, yes, but on its own it's not practically relevant | Comment on Facebook!

References:

• Bonmati-Carrion, Maria Angeles, et al. "Protecting the Melatonin Rhythm through Circadian Healthy Light Exposure." International Journal of Molecular Sciences 15.12 (2014): 23448-23500.
• Diepen, Hester C., et al. "Caffeine increases light responsiveness of the mouse circadian pacemaker." European Journal of Neuroscience 40.10 (2014): 3504-3511.
• Dumont, Marie, and Jean Paquet. "Progressive decrease of melatonin production over consecutive days of simulated night work." Chronobiology international 0 (2014): 1-8.
• Figueiro, Mariana G., 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 9 (2014): 1527.
• Fukushige, Haruna, et al. "Effects of tryptophan-rich breakfast and light exposure during the daytime on melatonin secretion at night." breast cancer 4 (2014): 9.
• Harb, Francine, Maria Paz Hidalgo, and Betina Martau. "Lack of exposure to natural light in the workspace is associated with physiological, sleep and depressive symptoms." Chronobiology international 0 (2014): 1-8. 
• Irwin Michael, R. "Why Sleep Is Important for Health: A Psychoneuroimmunology Perspective." Annual Review of Psychology 66 (2015): 143-172.
• Kayaba, Momoko, et al. "The effect of nocturnal blue light exposure from light-emitting diodes on wakefulness and energy metabolism the following morning." Environmental health and preventive medicine 19.5 (2014): 354-361. 
• Leichtfried, Veronika, et al. "Short‐Term Effects of Bright Light Therapy in Adults with Chronic Nonspecific Back Pain: A Randomized Controlled Trial." Pain Medicine 15.12 (2014): 2003-2012.
• Obayashi, Kenji, Keigo Saeki, and Norio Kurumatani. "Light exposure at night is associated with subclinical carotid atherosclerosis in the general elderly population: The HEIJO-KYO cohort." Chronobiology international 0 (2014): 1-8.
• Okamoto, Yosuke, and Seiji Nakagawa. "Effects of daytime light exposure on cognitive brain activity as measured by the ERP P300." Physiology & behavior 138 (2015): 313-318.
• Partonen, Timo. "Obesity= physical activity+ dietary intake+ sleep stages+ light exposure." Annals of medicine 46.5 (2014): 245-246.
• Shapiro, Bryan B., et al. "The Relationship Between Ultraviolet Light Exposure and Mortality in Dialysis Patients." American journal of nephrology 40.3 (2014): 224-232. 
• Thompson, A., et al. "The Effects of Evening Bright Light Exposure on Subsequent Morning Exercise Performance." International journal of sports medicine EFirst (2014).
• van der Lely, Stéphanie, et al. "Blue blocker glasses as a countermeasure for alerting effects of evening light-emitting diode screen exposure in male teenagers." Journal of Adolescent Health (2014).
• Virginie, Gabel, et al. "Dawn simulation light impacts on different cognitive domains under sleep restriction." Behavioural Brain Research (2014).
• Wang, et al. "UV light selectively inhibits spinal cord inflammation and demyelination in experimental autoimmune encephalomyelitis." Arch Biochem Biophys. (2014). [Epub ahead of print]
• Zeitzer, Jamie M., et al. "Millisecond Flashes of Light Phase Delay the Human Circadian Clock during Sleep." Journal of biological rhythms (2014): 0748730414546532.

A Cup of Coffee in the Bluelight District: Synergistic Effects of Caffeine + Blue Light on Psychomotor Effects. Plus: Yerkes-Dodson and U-Shaped Dose-Response Curves

This could be your new wake-up routine: Strong coffee and a bath in blue light.

"The abuse of ADHD drugs in people from all social classes is on the rise..." I guess you will have heard or read news like these several times over the past 12 months and in an article over at Forbes.com that was published on St. Nicholas' Day, Todd Essing even claimed: "Adderall use at work by the healthy to enhance cognitive performance is back in the news." Essing cites, among others, Stephen Petrow whose article over at The Atlantic is what Essing calls "a love letter to his 2-3 times per week Adderall use" - and a scary one for Petrow who is a psychologist by trade and says of himself that he "treats lots of hard-driving career-focussed 20- and 30-somethings". (Essing. 2013)

I guess Essing, whose previous article "When ‘Study Drugs’ Kill" took a reasonably critical stance towards the use of Adderal and similar drugs by healthy individuals, will be delighted by the results C. Martyn Beaven and Johan Ekström present in their latest paper in the peer-reviewed open access journal PLOS|One (Beaven. 2013). The intention of their experiment was ...

"[....] to compare and contrast the physiological responses to blue light and caffeine, administered both separately and conjointly. Measures of cognitive function, reaction time and wakefulness were assessed and it was hypothesized that similarities would be observed with the administration of 240 mg of caffeine and a 1 h dose of ~40 lx blue light." (Beaven. 2013)

Moreover, Beaven and Ekström assumed that combining the caffeine equivalent of two small or one large, strong coffees with the 'enlightening' power of a r  ~40lx  blue light LED light source (Techlight® RGB, 3W,  λmax = 470 nm) would induce alerting and psychomotor effects greater than either intervention in isolation.

What exactly did the scientists test for? The study participants had to complete a computer-based psychomotor vigilance test protocol (PVT) that consisted of 20 trials of a visual and audio Go/No-Go test, an Eriksen Flanker test, and 5 trials of a visual reaction time task (all tasks are available online at www.cognitivefun.net, so just try them out and judge for yourself how significant they are).

In view of the fact that you will probably have read the "Sunlight à la Carte" (read more) article I published as part of my Circadian Rhythm Series, you shouldn't be surprised by either, ...

• the experimental design that involved the ingestion of a gelatine capsule containing either 240 mg of caffeine or a visually indistinguishable sugar placebo with a small glass of water (CAF), the exposure to ~40 lx of blue light from a LED light source (Techlight® RGB, 3W, λmax = 470 nm) or a white light alternative (~100 lx) for 1 h (BLU) or a combination of both, or
• the assumption that caffeine and blue light should exert additive effects on both physical and psychological measures of alertness

... the effects of both caffeine and high frequency (=low wavelength) light have after all been discussed at length, here at the SuppVersity. What struck me (and maybe you, too) as odd, initially, though, was the assumption that "eye colour would influence the degree of the psychomotor and physiological responses to blue light" (Beaven. 2013), as well.

Figure 1: Eye color determines the extent of the melatonin suppressing effects of 2h of bright light exposure during the night. The effect is significantly stronger in "dark-eyed" Asians vs. "light-eyed" Caucasians (Higuchi. 2007)

The assumption that light-eyed participants would show a more pronounced reaction to light exposure is based on observations by Higuchi et al. (2007) who observed a direct link between eye color and the decrease in melatonin secretion in response to light, when they compared the effects of 2h of nightly light exposure in "light-eyed" Caucasians "with blue, green, or light brown irises" to Asians with "dark brown irises" (Higuchi. 2007).

Contrary to what you may have expected, the suppression was increased for the Asians (see Figure 1), not the Caucasians, of whom you'd argue that their ancestors lived at a latitude, where sun is scarce in the winter time, so that you'd have to make the most of it, when it shines.

If we now turn to the results of the study at hand, we'll see that Beaven and Ekström observed a very similar trend in their study, where he increase in visual reactions in the blue light only condition was significantly more pronounced in the blue-eyed, non-shift worker, non-smoking, low to moderate caffeine and alcohol consuming study participants (13 men, 18 women) than in their darker-eyed peers.

Figure 2: Effects of placebo (Pla), blue light (BLU), caffeine (CAF) or blue light + caffeine (BCAF) on psychomotor performance in 24 (13 male, 11 female) healthy subjects with a mean age of 26 ± 4 years; as it is common in science changes that were statistically significant are marked with letters, i.e. "a", "b", "c" (Beaven. 2013)

When they took a closer look at the caffeine (CAF), blue light (BLU) and caffeine + blue light (BCAF) treatment induced performance boosting effects you can see in Figure 1, the researchers from the Mid Sweden University observed a baseline advantage in reaction times in the visual reaction time task in male vs. female study participants (255 vs 274 ms; p = 0.0172). If you scrutinize the data in Figure 2, you will also realize that Beaven & Ekström are generally correct, when they state that their experiment is the first demonstration of distinct effects of caffeine and blue light on aspects of psychomotor function - it's after all hard to deny that (a) both worked and that (b) they did not have identical effects.

Beware of the consequences of the Yerkes-Dodson law

The researchers go on to explain that "[b]oth blue light exposure and caffeine ingestion improved accuracy in the visual Go/No-Go task", but that their combination "did not result in enhancement in the number of correct responses" (see Accuracy in incongruent task in Figure 2). For caffeine alone similar effects have been observed. These observations form the basis of the"Yerkes-Dodson law", in which it is postulated that the relationship between arousal and performance follows an inverted U-shape curve (Fredholm. 1999). Consequently, Beaven & Ekström suspect that

"[...], it is possible to rationalize that the combined treatment of blue light and caffeine dose exceeded the optimal state of arousal and consequently resulted in impaired accuracy." (Beaven. 2013)

At first sight, this hypothesis appears to conflict the improved fast reaction time the researchers observed in the visual Go/No Go task, but when you come to think about it, the stimulating effect of caffeine + blue light that is an advantage, when it comes to relatively simple tasks, may well be too pronounced for an exercise that requires a higher degree of mental focus / contentration.

Learn how to use light to modulate or realign your circadian rhythm.

So what we learn from the results? Actually there are two things you can take away from the study.

• It may well be worth to add a blue light lamp to your list of birthday, not Christmas presents. You do after all you want to have it before Fall 2014.
• You would be well-advised if you remembered "Yerkes-Dodson law" and the futility of a "more helps more" approach to cognitive enhancement.

Considering the fact that it's Christmas Eve this certainly isn't too bad as far as the total amount of subject matter or its quality is concerned - right? Apropos: Merry Christmas!

References:

• Beaven, C. M., & Ekström, J. (2013). A comparison of blue light and caffeine effects on cognitive function and alertness in humans. PloS one, 8(10), e76707.
• Essing, T. (2013). Managing The Risks Of Taking Adderall To Enhance Work Performance. Forbes.com. Dec. 06 2013 < http://www.forbes.com/sites/toddessig/2013/12/06/managing-the-risks-of-taking-adderall-to-enhance-work-performance/ > retrieved on 12-24-2013.
• Fredholm, B. B., Bättig, K., Holmén, J., Nehlig, A., & Zvartau, E. E. (1999). Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacological reviews, 51(1), 83-133.
• Higuchi, S., Motohashi, Y., Ishibashi, K., & Maeda, T. (2007). Influence of eye colors of Caucasians and Asians on suppression of melatonin secretion by light. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 292(6), R2352-R2356.
• Petrow, S. (2013). The Drugs of Work-Performance Enhancement. The Atlantic. < http://www.theatlantic.com/health/archive/2013/11/the-drugs-of-work-performance-enhancement/281055/ > retrieved on 12-24-2013.

Hack Your Biological Clock: Light-Induced Circadian Phase Shifts Work So Well That You Better Watch Out to Avoid Accidental Phase Shifting When You Check Your Mails

If you do it on purpose, "hacking" your biological clock can be highly beneficial. If you're doing it out of pure ignorance, though, you're in trouble.

In view of the impeding return to standard time, it's probably a good thing, in view of the iPhones, iPads and Facebooks of this world it could turn out to be a serious health problem, though: the ease with which you can "hack" your biological clock - on purpose, but also incidentally.

How easy it really is to turn the biological clock of life forward and backward has in fact only recently  been confirmed by Seong Jae  Kim and colleagues from the Northwestern University Feinberg School of Medicine and the Technology Evaluation Center of BlueCross BlueShield Association (Kim. 2013)

Fast forward / backward, please!

All the scientists had to do to make sure that the 29 healthy young (25.1 ± 4.1 years, M:F=8:21) and 16 healthy older subjects (66.5 ± 6.0 years, M:F=5:11) who participated in the said study experienced a 2h shift in the onset of their natural melatonin release was to expose them in a randomized order to 2h light pulses of 2 different intensities: 2,000  and  8,000lux)

Figure 1: Graphical summary of the implications you of the data from Kim et al. (2013)

As you can see in the graphical illustration of the implications in Figure 1 the scientists used the core body temperature minimum (CBT_min) of their subjects as a reference.

Suggested Read: "90 Min Sleep Restriction - How Bad is It Really? Changes in Insulin Resistance Last For One Week" | more

"Subjects were admitted for four nights and three days under dim light during daytime hours with eight hours of sleep in dark at their habitual time (dark bars). Blood samples were taken throughout the baseline and post -treatment nights to assess lightinduced [sic!] changes in the circadian melatonin rhythm.

On the third night, subjects were exposed to light at one of 3 time points ( -8h, -3h, or 3h) relative to the core body temperature minimum (CBTmin) measured on the baseline night. They were exposed to a 2-hour light pulse (including a 15 min ramp up and ramp down) of 2,000 lux on one laboratory stay and 8,000 lux on a different laboratory stay, in a randomized order, separated by at least 3 weeks." (Kim. 2013)

I guess it may come as a surprise that the scientists were able to show that the effect size / efficiency of the procedure was significantly influenced by the time of pulse, but not by its intensity, the age of the subjects or interactions between age and intensity, or time of pulse and intensity.

What did make a difference, though was the lag (=length of the time shift that was achieved), though.  Administered -8h before core body temperature minimum (CBT) the average phase delays  were -0.72h for  2,000lux and -0.50h for  8,000lux. When it was administered +3h after the CBT the researchers observed only a minimal phase advance of +0.05h for  2,000lux, while the 8,000 lux light produced a phase shift of + 0.18 h. In both cases the standard deviations were however so large that a significant difference could not be found.

8h is where the sweet spot it + phase advances are difficult to achieve

The "wake-up protocol" (Figure 1, 2nd row on night 3), in the course of which the subjects were woken up 3h before the CBT and thus while they were already sleeping had paradoxical and unpredictable effects:

"Light exposure targeted 3h before CBT min was distributed in both phase delay and advance regions  (-3.2h to +2.5h) relative to the melatonin midpoint." (Kim. 2013)

Needless to say that this is not a suggested protocol, but a good example of the mess that happens, when your sleep gets interrupted by light exposure.In other words, the procedure is identical irrespective of your age and the "power" of the lamp you use - the one thing that counts is the timing of the pulses.

How intense is the light around me? In order to give you a better idea of how intense 2,000 and 8,000lux are, I've compiled a couple of reference values:

• Dim interior lighting < 100 lux
• Residential indoor lighting < 500 lux
• Bright indoor lighting (e.g. task lighting, kitchens, offices, stores) < 1,500 lux
• Sunlight + cloudy sky + shadow < 5,000 lux
• Sunlight + in shadow < 10,000 lux
• Full, but not direct daylight daylight < 25,000 lux
• Outdoor direct sunlight < 120,000 lux

Don't forget that the frequency (=color) of the light is about as important as its intensity; only blue / green light and light with blue and/or green components (e.g. the light of an LED display) will get the job done.

In the discussion of their results, the researchers point out that their findings are in line with previous studies by Duffy et al. (Duffy. 2007), ...

"[...]who found that there was no difference between young and older adults in the magnitude of  phase delays of the melatonin rhythm following 6.5 hour light exposure of more than 1,000 lux." (Kim. 2013)

They also reference a study by Sletten et al. (2009) that compared the effectiveness of blue and green light in young and older adults. In the said study, the researchers determined that the phase advances in response to blue light were  slightly larger than advances in response to green light in both young and older adults. The perceived effects on subjective alertness and sleepiness, on the other hand, were significantly more pronounced in the younger participants in the blue light condition.

As Kim et al. point out, their own previous analysis seem to indicate that blue light is much more effective, when it comes to the induction of phase advances than green light - in fact, in one of their studies, the exposure the use of green and red light did not yield satisfying results at all (Green. 2004).

So does this mean you have to use one of the fancy blue-light lamps?

Despite the fact that there is little doubt that "blue" (~430nm) light is more effective than green light and that red light does not work at all, you may be shocked to hear that running Facebook on your laptop screen is probably enough to get the job done.

The reasons are simple: Firstly, what you see there is "blue" or at least "blueish", anyway. More importantly, however, the fancy LCD and LED displays in modern notebooks, tablet PCs and smartphones have an outstanding luminosity (=they are bright enough) and, as you can easily see in the graphs below, "blue enough".

WLED

GB-LED

How bad is it? It really depends on the "how blue" your screen is going to be. Many cheaper LED monitors use the "blueish" WLED technology - the "true color" GB-LED displays are mostly used, where true color actually matters - in print and design.

The spectral data does also tell you that you will never "lack" blue light to convince your body that it's time to rise and shine, not time to sleep, even if you have one of the modern "true color" displays. Much contrary to the clock in the lower right of your screen, your biological clock will thus basically freeze in "daylight mode" the very moment you sit down in front of your screen.

Yes, things can become worse - you don't even have to sit there for hours

I know what you're thinking, you, a SuppVersity Veteran from hour one, obviously new all that and the only thing you do after 8PM, to make sure you can be in bed ad 10PM and get your 8h of sleep before you have to shower at 6AM on the next morning is to check the occasional text massage on your phone, right? Well, bad news:

"According to published data, a phase shift is often not completed immediately after a light pulse (Pittendrigh et al., 1958; Watanabe et al., 2001)." (Kim. 2013)

Actually the saturation effect, i.e. the presence of identical phase shifts for 2,000 and 10,000 lux, confirms it: It does not take hours to biohack yourself!

It goes without saying that this is a good thing, if you actually plan to advance / delay the onset of melatonin release, it is however a serious problem if you "just head back to check your emails" right before you are heading to bed.

So how do you "biohack" your rhythm, then? If you want to try the no guesswork approach, the first thing you would have to do is to try and find your core body temperature minimum. Unfortunately, this is - despite the existent correlation with oral, rectal and gut temperature - not an exactly easy undertaking, as it will occur right when you are supposed to sleep, not to fumble around with a thermometer.

Use fasting another means to sync your internal (light control) and peripheral biological clock. Learn more in the last installment of the Circadian Rhtythmicity Series: "Intermittent Fasting (Re-)Sets the Peripheral Clock" | read more

So we just assume that his would be at ~4am (where it should be if you lived by the natural clock, i.e. sunrise and -set), which would mean that you would be able to master ...

• the impeding -1h phase shift on Sunday (US 11/03 vs. EU 10/27) at 3:00 (AM) by sitting in front of an appropriately bright light from 6pm to 8pm, and  
• the subsequent +1h phase shift in spring by sitting in front of a bright light on Thursday, Friday and Saturday morning at 7am for 2h

Actually, both does not appear so difficult, right? And I bet that some of you are in fact inducing a decent phase delay on a regular basis when they sit in front of a bright computer or television screen after sundown. Am I right? If so: Is it really any wonder you always wake up unrefreshed when your alarm clock rings?

References:

• Longo DL et al. Harrison's Online. Featuring the complete contents of Harrison's Principles of Internal Medicine, 18e.
• Kim SJ, Benloucif S, Reid KJ, Weintraub S, Kennedy N, Wolfe LF, Zee PC. Phase-shifting Response to Light in Older Adults. J Physiol. 2013 Oct 21. [Epub ahead of print]
• Sletten TL, Revell VL, Middleton B, Lederle KA, Skene DJ. Age-related changes in acute and phase-advancing responses to monochromatic light. J Biol Rhythms. 2009 Feb;24(1):73-84.