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If you're looking for ATS work lights hit the back button on your browser (or "Home" button above, and click on the "Products" button.) THE IMPORTANCE OF HAVING BRIGHT LIGHTING: Bright lighting is important for many reasons; clearly (pun) the ability to see better would be the most obvious since this directly impacts work quality and safety (if you can’t see clearly, how can you possibly guarantee good work or safety?), There are some IES Recommended lighting levels for various tasks listed at the bottom of the page. There are also some less obvious, but equally important reasons for having bright lighting if you work at night: As simple as it sounds, a brightly lit work area is the single most important factor in keeping night shift workers alert and safer as well as happier and slimmer. It has to do with the brains internal clock and how it uses bright light cues from the environment to control the alerting or sleep inducing neurotransmitters serotonin and melatonin (The same principles apply to people suffering from insufficient light on the day shift as well):The SCN, the Brains 24 hr clock: Bright lighting is doubly important for nightshift workers or anybody who needs to stay alert at night. Having a brightly lit work area will keep night workers alert, and therefore safer and more productive. Why you ask? Well it has to do with Serotonin and Melatonin and how the brain uses these hormones to either put the brain to sleep or wake it up. The levels of these hormones are controlled by the brains daily clock, the Suprachiasmatic nuclei (SCN). The SCN is a cluster of about 10,000 cells just in front of the hypothalamus, near where the optic nerves cross over behind the eyes (the SCN gets input directly from the eyes by way of some specialized optic nerves) The SCN cluster of cells puts out a signal which varies sinusoidally (in a sine-wave form) over a 24 hr period, which then controls Melatonin levels. Melatonin is the hormone responsible for putting you to sleep. Melatonin levels follow the sinusoidal SCN variation, rising in the evening to put the brain to sleep (for people on a regular day shift that is), with a peak Melatonin output occurring at 3 or 4 am (again for people on a regular day shift). The SCN is in essence an oscillator with a natural frequency of about 24 to 25 hrs. If you’re familiar with stringed instruments, you’re probably also familiar with how plucking one string will cause an adjacent one (of the same note), to oscillate in unison. The SCN is just an oscillator, albeit with a very long cycle, which reacts the same way to light and dark variations. To get it entrained well, the subjective day needs to be bright, and the subjective night, dark. The brighter the subjective day is (night time for night shift workers), the sooner and better the entraining will be. By better entrained I mean the SCN has a higher amplitude, which corresponds to higher alertness during subj. day and better sleep during subj. night. Avoiding too much light during the subj. night is important too; both for ensuring a good amplitude and for reducing shifts in the cycle. The one exception would be if you’re trying to shift your cycle such as when you have jet lag or are changing shift times, in which case the fastest way to get to a different cycle is to first squash the SCN amplitude. Bright light during the subj. night squashes the amplitude and makes the SCN very susceptible to phase shifts. Of course if you don't want to shift your cycle to a new time, then of course you want to avoid bright light during your subjective night (ie keep it dark). This can be particularly tricky for night shift workers who drive home or otherwise spends time in direct sunlight during their subj. night (100,000 lux facing the sun, & approx. 10,000+ lux looking sideways to sun). To avoid unwanted shifting it is doubly important to get a good amount of light during the subj. day to keep the amplitude up and in sync. Getting a good amount of light during a workers subjective day, means simply having a well lit work area, since this is where a person spends their subjective day! The principle of keeping your work area bright also applies even if you do want to shift your cycle; whether you’re a businessperson visiting a new time zone, or a military unit transferred to a time zone way around the world, having a well lit work place during the new subj. day will first squash the amplitude & then shift the SCN phase to the new cycle or time zone. There are of course optimal methods to accomplish this in the least amount of time; e-mail for the name of a company which specializes in phase shifting. They shift NASA’s astronauts before they go up. If you don’t need the fastest phase shift, just having bright lighting on your new subj. day will get you there within 3-5 days (optimal shifting can be done within about 2-3 days). The Serotonin Melatonin connection Now you’re probably wondering about the connection between Melatonin and Serotonin. What most people don’t know is that they are so chemically similar that the brain uses one to make the other. Melatonin is exactly the same base molecule as serotonin, but is has a slightly different side chain, which means melatonin Must act as selective serotonin antagonist at certain serotonin receptors, ie the melatonin "key" fits into the same receptor as serotonin, but because of the different side groups, it can't "turn" in the receptor "lock" and therefore can't activate it.. (think of a door key that almost works; if its jammed into the lock but can't turn, then now the real key can't get into the lock to activate it, so the lock is now deactivated). Hence, although they are almost the same molecule, they have opposite effects on the brain. Melatonin and Serotonin have a kind of a yin and yang type of relationship; Melatonin is the sleep hormone which promotes a well rested mind, necessary for well being, and Serotonin is a master neurotransmitter affecting alertness and activity (it controls the levels of other neurotransmitters). In general when levels of one are up, levels of the other are down. This makes intuitive sense; you don’t want to be sleepy and active simultaneous. Tryptophan, by the way, is the body’s precursor for both hormones. Melatonin levels are of course controlled by the daily clock, the SCN (by means of the hypothalamus etc.). When Melatonin is being produced it is being produced at the expense of Serotonin, since the brain is busy converting Serotonin to Melatonin. Light, in addition to controlling Melatonin and Serotonin levels indirectly through it’s affect on the SCN cycle, can also have a fairly direct effect too; Within a fairly short time (maybe an hour or so) of receiving 2,500 lux, (through the eyes) Melatonin secretion is halted (with a corresponding stop in depletion of Serotonin) The light level and time required varies from person to person. It’s interesting to note that humans are the only species (with the possible exception of domesticated dogs) that don’t respond much to lower light levels. I’m guessing that when cavepeople started using fires at night, those people (and dogs) who didn’t get affected much by this new source of light at night, were able to get enough sleep & handle fights with the elements better (and hence get the opportunity to pass along their more light immune genes). The yearly cycle, the SAD connection The connection between Melatonin and Serotonin also explains Seasonal Affective Disorder (SAD). In the winter months when days are short and light levels lower, the brain puts out more Melatonin. This is probably a combined effect of a lowered SCN amplitude, (which doesn’t completely stop melatonin output during the day), combined with the fact that there’s less chance for bright light to directly fend off the remaining melatonin during the day (due to shorter day light hours, and dimmer light in winter). The extra Melatonin is of course is at the expense of Serotonin. The combination of more Melatonin and less Serotonin makes people sleepier, moodier and less active overall. The amount of sensitivity to SAD type Serotonin reduction varies from person to person. Higher sensitivity is probably linked to heritage from northern extremes, but the connection isn’t clear cut; Some studies have shown that Scandinavians have a higher incidence of it, but it’s not clear whether the high incidence is due to their heritage or due to their location; Most people, regardless of heritage, will succumb to it to some degree up at the arctic circle (where the sun sets completely for months). So if bright light stops the Serotonin to Melatonin conversion, why does it take so many days to feel the effect? The answer is in how the Serotonin receptors adjust to new amounts of Serotonin; unlike other neurotransmitter receptors, which become desensitized over time when exposed to higher levels, Serotonin receptors actually increase their sensitivity over time when exposed to higher levels. The number of receptors on each nerve ending changes in response to the new Serotonin levels, making the nerve More sensitive to Serotonin as levels increase. The adjustment time is about 12 to 14 days, with about 1/2 the effect in place by day 10. Why did SAD evolve? In cavepeople days it was an advantage to conserve energy in the cold, food scarce winter months. It’s the same reason bears hibernate through the winter. Undoubtedly, bears have extremely high levels of Melatonin along with low Serotonin throughout their hibernation. The lag in adjustment of the receptors prevents bears and Vikings from getting too excited at the occasional bright warm winter day (foraging for food or trying to explore the world in the dead of an arctic Winter has it's drawbacks). The lag also works the other way; it prevents people from getting too depressed and inactive over the occasional cloudy day in Spring & Summer. As you probably already know, lowered Serotonin makes people moodier and hungrier. People tend to put on weight as the days shorten, much like bears getting ready for the winter (and interestingly many choose tryptophan rich turkey, for the holidays.. milk & your favorite holiday sweets will also boost tryptophan.. as well as you waist line of course). It’s interesting to note that night shift workers in addition to being sleepier on the job, also tend to have snack cravings and weight gains more than other workers; If they don’t get enough light they are constantly in hibernation mode. Alertness and Safety The biggest problem for night shift workers or course isn’t their waist line, but rather maintaining alertness. Night time drivers, in spite of having the least congestion, have by far the highest rate of accidents per cars on the road. This accident rate peaks at around 3 or 4 am which corresponds with peak Melatonin output for most of us. The exact same set of problems that caused Three Mile Island had occurred on the dayshift in a year prior to the accident; the day shift people figured out the faulty reading in about 15 min and corrected it. When it later happened to the night shift, near the 3 or 4 am low point, they couldn’t figure out that it was a faulty meter reading. They took action based on faulty judgement about conflicting meter readings.. When the dayshift came in bright eyed & alert, they figured it out in a few minutes, but by that time the meltdown was already in progress. Chernobyl was also a nightshift meltdown. The Bhopal chemical disaster, and the Exxon Valdez oil spill were both night shift disasters as well. Well you get the point, whether it’s a construction job or an emergency room, it pays to have enough bright light to keep people alert. The Bottom Line on Bright Lighting: Just ensuring a good light level at work (and especially on the night shift), will allow workers to entrain their 24hr cycle clock (SCN) to the work cycle, and will also produce a high enough amplitude in the SCN output to ensure Melatonin suppression at work, combating drowsiness on the job. The Melatonin suppression in turn, also allows reasonable Serotonin levels and therefore enhances worker happiness, safety and productivity. And of course brighter lighting just plain allows workers to see more clearly which also enhances safety, quality and productivity.
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