It's pretty clear that working the night shift is bad for your health. For example, it increases your risk of heart attack . One of the specific ways it increases your risk is through your blood pressure. Working the night shift seems to elevate your blood pressure more than working during the day. It is clearly a bigger problem for African-Americans.
Why does this happen? It's not entirely clear yet. We do know that the strain of working nights increases your adrenaline levels, and higher adrenaline levels increase your blood pressure. The night shift also might reduce your arteries' ability to constrict and relax when they need to - impaired endothelial function, as the physiologists call it.
Another factor may be that working the night shift gives you a sense of being inferior to the day shift. The stress of feeling inferior may cause elevated blood pressure.
What can you do? If you're going to stay on the night shift, you should sleep as much as you can. Treat sleep as a sacred time. Teach your family not to wake you up. But if you want to maximize your health, you also need to take extra preventive steps, beyond what a daytime worker would do.
For blood pressure, I would suggest checking your blood pressure regularly. Invest in a blood pressure monitor. (You can get one for about $50.) You should check it at home after you've been sitting still for a few minutes. It's a good idea to check it at work once in a while also. If you work in health care, ask someone to check your pressure. If you don't, it might be worthwhile to bring your monitor into work once in a while to see how high the numbers go.
Take all the numbers in with you to your next physician visit. Expect that, at some point, you may well need medication. It's worth it to protect yourself.
It's obvious to those of us who have been there, but to normal daytime people, the night shift is invisible. It's a dirty job, after all; best not to think about it. For the beneifit of the normal diurnal types, I'll cite some scientific studies on the negative effect of working the night shift on several variables of life quality.
Researchers have show that night shift workers burn out more and have more emotional exhaustion. They have higher job stress, higher life stress, and more anxiety and depression than daytime workers. Employee turnover is higher, so it's hard to keep the night shift staffed. Productivity is lower, especially at about 3:00 a.m.
There are more accidents at night, especially among people with rotating shifts, and after midnight, and after the eighth hour of work. The Bhopal chemical disaster in 1984 occurred at 12:40 a.m., and the Three Mile Island disaster in 1979 occurred at 4:00 a.m. (See Melbin.)
So working the night shift feels bad, is dangerous, is less productive, and hurts your family. It's also bad for your health, by the way. Why do people do it, then? Generally it's for the money, or because of lack of seniority, or to get away of an oppressive daytime boss, or to keep one spouse home with the kids 24 hours a day, or just because the worker is a "night person."
Humans started out mostly being daytime creatures, as I understand. We invented fire, then gaslights, then electricity, and somewhere along the line we invented nighttime work. Night has always been a fearful place, something to look out into from the comfort of the fire. Moving into it, charting it, dominating it, are processes of colonization. Night is a frontier, as has been written.
On the frontier, the process of law is less active. With fewer people and more space, it must be so. So we see rules treated casually. Hierarchy is flatter. Bureaucracy is more lenient. You can get away with a loose tie or an informal comment to your supervisor. But with the law being less active, there is more chance for significant crime. We all know this; we all know to be careful after dark.
People felt to be vulnerable are kept indoors at night, or at least kept at home. That's what we see right now in India, where women are now moving away from the night shift after the brutal gangrape and killing of a woman on a bus in Delhi. They're afraid to to work at night and are going home earlier. They're being moved off night shifts by their bosses, sometimes to the detriment of their careers.
This is wrong. The answer to a lawless and prejudicial frontier isn't to withdraw from it. The answer is to push the forces of order and law into it.
This is the course of history, and it's not going to be stopped by one crime. It is a blessed rage for order, as the poet says, which
Mastered the night and portioned out the sea,
Fixing emblazoned zones and fiery poles,
Arranging, deepening, enchanting night.
Researchers in Seoul have shown that this works to improve your alertness, and makes your sleep better during the day. They took 12 nurses on the night shift and put them each through three separate situations: exposure to normal room light at night, exposure to bright light from midnight to 5 a.m., and exposure to bright light plus wearing sunglasses in the morning to keep sunlight out of the eyes. (The bright lights were 4,000 to 6,000 lux, and about 3 feet from the eyes of the nurses, if that means anything to you.) They measured sleep quality using a wrist monitor, measured subjective sleepiness using a questionnaire, and measured cognitive performance with computerized tests.
The nurses with the bright light exposure at night, plus protection from sun in the mornings, did better on sleep quality and alertness. Cognitive performance seemed to be better, but the results didn't reach statistical significance.
Other studies have confirmed that you can switch your body clock (circadian rhythm) to the night shift using light exposure strategically.
It's probably not practical for most people to install a bright light by their workspace at night, but if you can, it will help. Otherwise, I'd try to stare into bright lights as much as you can, maybe moving somewhere advantageous during breaks.
And definitely wear sunglasses in the morning when returning home. Then sleep in a room that is as dark as possible. Put heavy shades over the windows. Wear a sleeping mask. Put a mattress in a large closet. Do whatever you can do.
Even a little bit of light suppresses melatonin, and melatonin helps you sleep.
It's important not to make mistakes at work. Consequences of a mistake can range from a problem with the cash register to life-and-death catastrophe. When we are conscientious, we try to watch ourselves for mistakes as we work. This becomes much harder when we are fatigued.
Sleep deprivation causes a cognitive impairment that is not noticable. We do more poorly on tasks, but can't tell the difference. This may be similar to how some people can be quite intoxicated with alcohol and be unaware of significant impairment. A corrolary to this is that if you are sleep deprived, you can gain some practical intelligence just by getting enough sleep.
During sleeplessness, we also get brief interruptions in our consciousness, lasting a few seconds. Our minds can't stay concentrated for long periods of time without suffering from these interruptions. It's as if our minds have to re-orient themselves constantly. There is great variability in the ability to concentrate as the brain's sleep instincts fight with the need to stay awake.
So when we're sleep deprived - and most people on the night shift are sleep deprived - we lose some of our practical intelligence without knowing about it, and we have micro-interruptions in our stream of consciousness that predispose us to errors.
Basically, we get stupid and error-prone when we work the night shift.
My personal experience is that carbohydrate rich foods make me more fatigued at night. But I don't think this is universal. Some people seem to use carbohydrates as a way to stay awake - they snack on bread and chips, for example. So there is probably individual variation, in the same way that some people crave carbohydrates and some don't.
From the literature, it does look like high carbohydrate meals overall make you more drowsy. Compared to high protein meals, high carbohydrate meals impair reaction time and attention. On the other hand, a high protein meal makes you more easily distracted. In my view, it doesn't make any difference if you're not distracted if you're asleep, so I like the high protein option.
In one lab experiment, a group of men was kept awake for 24 hours and fed high carbohydrate and high fat meals. High carbohydrate diets led to more fluctuation in performance levels and in sleepiness.
The only study I found directly looking at diet under real night shift conditions involved 21 workers at hospital in Jerusalem. The workers were given high carbohydrate, high protein and normal meals on separate nights and were given psychological testing after each meal. There was no meaningful difference between the diets, though it seemed that a high carbohydrate diet actually was more beneficial.
Probably every individual needs to experiment on themselves to find the optimal night shift diet.
The short answer is that there is probably higher risk of slow development in the womb, miscarriage and preterm birth.
There are several ways to measure pregnancy risk. You can look at risk of miscarriage; of having a baby that is slow to develop in the womb (“small for gestational age, ” or SGA); of having a small baby at the time of birth (“low birth weight”); or of premature delivery.
The literature contains a few meta-analyses on this subject. This type of study combines data from multiple other studies and tries to estimate risk with more reliability than is possible with single studies. More data means more accuracy of the estimate, and less uncertainty.
Let’s break it down. In a 2011 meta-analysis, pregnant women doing shift work – loosely defined as either rotating shifts or night shift work – had a possible higher risk for preterm delivery. The initial estimate was a 16% increase in risk, but this estimate dropped to essentially zero when low quality studies were removed from the analysis. There was no significant risk of low birth weight or preeclampsia., but SGA risk was 10% higher in night shift workers.
The risks listed above were statistically significant, which means that while the numbers may not be exactly right, there is a 95% chance that there is some kind of real risk.
Why would this happen? It may be that the stress hormones released over the night shift, such as adrenaline and cortisol, negatively affect the pregnancy. Also, shift work disrupts melatonin levels in the blood, and melatonin function is necessary for a healthy pregnancy.
It turns out this hasn’t been extensively studied. But the data we have suggest that it might be so.
We know for sure that sleep deprivation in the short term (meaning days to weeks) makes it hard to think and function. This is not controversial.
But we have a bigger problem, scientifically, if we want to figure out the effects of longer-term hazards to a human being. You can’t run a five-year experiment in controlled conditions on humans, for ethical reasons. So we’re left with observational data – just measuring people at different points of time, crunching the data and trying to figure out if one thing might be causing something else.
This method has its weaknesses, but it can be tremendously useful. It’s how we found out that smoking causes lung cancer, for example. Nobody ever did a controlled experiment on humans to study this.
Anyway, there’s one study on chronic insomnia sufferers that shows a loss of brain tissue in the orbitofrontal area, which is involved in problem solving and decision-making.
Another potential piece of evidence comes from the Whitehall study in the U.K. This is a famous long-term observational study of civil servants that has generated many publications over the years. A 2009 analysis showed that working more hours per week was associated with two measurements of intelligence. One was vocabulary, which measures a “crystallized” intelligence – a familiarity with ideas. Apparently the more hours you work, the fewer things you learn about outside of work. The other test measured reasoning ability, or “fluid intelligence.” This is your general ability to process information. Fluid intelligence usually peaks in one’s 20’s, and declines through the rest of life, especially after age 60. Working extra hours seems to make you less intelligent, one way or another. It’s true that having long hours isn’t exactly the same thing as working the night shift, but it’s similar, and so I think it’s suggestive.
So if there is brain damage from shift work, would it be permanent and irreversible? No one knows, but I’d bet some of it is.