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The Science of Great Sleep

Too busy to read the whole article? [4,500 words, a 23-minute read] Here are the key takeaways:

  • Try to sleep 7-8 hours a night.
  • If you sleep better, you’ll be better at regulating emotions, remembering things, working out, and not overeating.
  • To get a better night’s sleep: (1) exercise (2) don’t drink before bed (3) keep your bedroom lights dim (4) avoid gadgets with a screen (5) find a comfortable pillow and (6) try sleeping on your right side.
  • Benadryl and Unisom can help you fall asleep every once in a while, but herbal supplements haven’t been very effective in trials.
  • Artificial dawn alarms can help you feel less sleepy in the morning. But, snoozing any alarm is probably a bad idea.
  • If you didn’t get enough sleep, try a 10-minute nap, a cup of coffee, stretching, or taking a walk.

Tytus Wilson, 27, an entrepreneur in Louisville, Ky estimates he’s spent over $20,000 over the last three years on products to help him track and improve his health. Sleep is a big part of that.

He’s experimented with things like blue light-blocking glasses, a grounding blanket that directs electrons from the earth into the human body, and magnesium supplements to improve his sleep. He’s also tracked the impact of diet, moods and daily steps on his sleep.

He says he realizes some of it sounds ridiculous.“I don’t spend any money on houses, cars and furniture,” he says. “If somebody tells me ‘This will help your sleep.’ I don’t care what it is, I’ll try it and see what happens.”

Wilson is probably an outlier, but sleep is a big concern among millennials. 43%  rated their sleep quality as “fair or poor” in an American Psychological Association poll. We’re more likely than older generations to stress about sleep quality too. 1

Robin Haight, a clinical psychologist in Tyson’s Corner, Va. attributes that stress in part to the internet. “Millennials have more access to information about wellness and health than perhaps older generations had at that same age,” she says. Even at 3 AM—when you’re lying awake in bed, you can go online and find articles citing research that links lack of sleep with things like decreased vaccine effectiveness2 and increased risk for Alzheimer’s Disease.3Haight adds that the increase in research and awareness about sleep can be a good thing, though.

Ever wondered how your sleep compares to everyone else’s? Here’s what a “normal” night’s sleep might look like in healthy 20-somethings:

  • Time to fall asleep: 6.3 minutes
  • Time spent in bed vs. time asleep (sleep efficiency): 6.6 hours to 6.2 hours (94%)
  • Awakenings per hour: 1
  • % of night spent in non-REM sleep: 72.3%
  • % of night spent in REM sleep: 22.2%


Is a good night’s sleep really that important?

Here are some of the ways sleeping better makes life more pleasant:

Sleep helps keep you from freaking out about the small stuff. Brain scans taken when sleep-deprived people viewed photos with negative subject matter showed more activation in the amygdala (a part of the brain involved in emotional reaction)5 than in people who’d slept normally. The sleep-deprived people also had a loss of connection between the amygdala and the medial prefrontal cortex, a part of the brain that can help moderate emotional reactions.6,7

To put that in a context that’s closer to real life, people in a study who had their sleep cut by 33% for an entire week reported mental fatigue and emotional instability that worsened over the week.8

Sleep is also good for your memory. A research review cites 35 studies that link inadequate sleep with declines in memory encoding (creating new memories) and memory consolidation (incorporating new memories into long-term memory).  Many of the studies found that people were better able to remember things like a string of letters or solutions to math problems after a night’s sleep.9

Sleep can help you get the most out of your workout. Sleep deprivation can significantly decrease your reaction time, which is important in activities like team sports or weightlifting.10

In another study, players on the Stanford University men’s basketball team improved their shooting accuracy, sprinted faster and reported feeling better overall during games after 5-7 weeks of increased sleep.11

New York-based Hannah Jiang, 23 says sleeping well helps her in her running, biking and other cardio workouts. “If I get the perfect amount [of sleep] like 8 hours and I’m eating well, and I’m working out well, everything is just better. My attitude is better too,” she says.

Sleep can help prevent weight gain. A handful of studies have found an association between shorter sleep hours and obesity. Possible explanations for the correlation: increased calorie intake due to more production of  hunger hormone ghrelin and less production of satiety hormone leptin. Or more available hours in the day to eat. You can’t munch at midnight if you’re not awake. Another explanation: sleep-induced fatigue or reduced ability to regulate body temperature could make working out a lot less appealing.12

In one study, people stayed in a sleep lab for 14 days and were allowed to sleep either 5.5 hours a night or 8.5 hours, the 5.5 hour group ate more snacks, on top of regular meals.13

Beauty sleep might be a real thing. Viewers perceived photos of people who’d slept well as more attractive and healthier looking than photos of the same people who hadn’t slept for a night.14

Now that we’ve established why better sleep is a good idea, let’s talk about the nitty gritty of how to actually sleep better.

Better sleep: What should you do throughout the day?

Make your bed in the morning. Jiang says she tries to as part of her strategy to keep her bedroom uncluttered.  “I try to make [my bedroom] as sort of zen-like as possible—otherwise I find that my mind is all over the place,” she says. “If I have stuff from work that I bring home, I try not to do it in bed because I find that I’m thinking about it.”

She may be on to something. Maybe it’s the old adage that a clean room leads to a clear mind. Or maybe well-made beds just look more inviting. Either way, research shows that people who make their beds every or almost every day are more likely to sleep better at night (though this is at best correlation, not causation).15

Exercise. Remember that better sleep can help you be a better exerciser? It can work the other way too, says Max Hirshkowitz, a professor at Baylor College of Medicine. “If you think of what we call the three pillars of health, which is diet, exercise and sleep, any one of those can improve the others,” he says.

A good reason to step up your workout: in a poll by the National Sleep Foundation, vigorous exercisers (runners, cyclists, swimmers and competitive sports players) reported falling asleep more easily, staying asleep all night, and waking up refreshed more often than people who do less intense workouts. But don’t give up on yoga or walking yet. Moderate and light exercisers said they have better sleep than people who don’t work out at all.

Hirshkowitz, lead advisor on the poll, doesn’t know the reason behind this, but hard workouts may also act as a buffer against bad sleep. Vigorous exercisers reported less impairment in their work, social and sex lives when they didn’t get adequate sleep.16

If you already exercise, but want to try to improve your routine for maximum sleep benefit, Hirshkowitz recommends exercises that improve conditioning as opposed to strength.  “If you’re running, I would say run a little faster, but maybe further to increase conditioning. If you’re doing weights, I would say doing more reps,” he says. He emphasizes building your routine gradually, as injuries can wreck your sleep and undo any benefits.

Cocktails at happy hour and nightcaps might not be a great idea. “Most people kind of believe that [alcohol] helps you sleep and no one’s been able to actually prove that in a lab,” says Eliza Van Reen, a professor of psychiatry and human behavior at Brown University. Her experiments indicate that just one drink can mess with your sleep. Participants who had a vodka tonic around 4 PM17 as well as at 9:30 PM18 had more difficulty getting to sleep than those who had a placebo.

But maybe you remember a time where you’ve had a few drinks and gone to sleep with no trouble. A review of 80 years of research (conducted between the 1920s-2010s) on alcohol and “normal” sleepers found that low (1-2 drinks), moderate (2-4 drinks) and high (4+ drinks) doses of alcohol tended to decrease the time it took to fall asleep. However, moderate and high doses caused a reduction in deeper, restorative REM sleep.19

Get out. Psychologist Robin Haight recommends getting outside for at least 15-20 minutes each day. “Being indoors for the majority of the day can actually interfere with the sleep-wake cycle,” she says. Sunlight exposure jumpstarts the body’s production of melatonin, the hormone most responsible for the regulation of sleep cycles.20

Better sleep: The critical hour before bed

On average, millennials go to bed around 11:58 PM.21 So let’s say it’s 10:58 p.m. Maybe you’re sleepy, maybe you’re not, but you know you should go to bed soon. Now is a good time to turn down the lights.

In dim light, melatonin can start doing its work over an hour earlier than in normal room light.22 How dim should your room be? Researcher Joshua Gooley says you should still be able to read a book, but that the fine print might be difficult. To achieve the ideal pre-sleep lighting level, Gooley recommends using a bedside lamp or putting a dimmer on overhead lights.

After making sure you’ve got sufficiently dim light in the bedroom, pay attention to your bathroom light. If you take a shower at night, or spend any other amount of time in there, bright white light can end that peaceful, sleepy feeling created by a dim bedroom. Warmer, or more yellow light (or a dimmer on the white light) is less jolting.23

Get rid of anything with a screen. The relatively bluer light from computer and tablet screens can interfere with melatonin production more than any other type of light.24There’s no clear answer on how much blue light exposure it takes to suppress melatonin. One study says 5 hours.25 Another says 1-2.26 A general guideline is to avoid bright screens 2-3 hours before bed.27Or, if you absolutely can’t do that, try blue light-blocking glasses or programs that change the color of your screens.

Besides the light factor, there’s the distraction of having a device right by your side that you can use to communicate with anyone, at any time. 67% of 19-29-year-olds say they take their phones to bed.28 Not surprising, right? If anything, that percentage seems a little low.

The most popular use of the cell phone in bed? Texting. Unfortunately, people who text in the hour before bed every night or almost every night are less likely to say they get good sleep, and more likely to be classified as “sleepy” on the Epworth Sleepiness Scale.29

If you absolutely have to take your phone or iPad to bed with you (and I’m guessing you are—habits die hard) turn the brightness down and hold it at least 14 inches away from your face. This reduces the brightness to a level that doesn’t mess with melatonin production as much.30 Airplane mode is probably a good idea too.

Better sleep: Sleep environment (your bed and bedroom) matters

So what exactly is a comfortable bedroom environment? 25-34-year-olds said in a National Sleep Foundation Poll that the top three environmental factors in their are: pillows, bedroom darkness and bedroom temperature, in that order.31


If the importance of pillows inspires you to go shopping, be prepared to be overwhelmed. On Amazon alone, there are 11,210 results for “pillow” in the “Health & Personal Care” category.

There’s pretty much no objective way to define a “good” pillow. One study recommended a pillow with an indentation to support the neck for people who tend to sleep on their back or side. 32 Another found that rubber pillows got high marks for general comfort.33 Another said anything but feather pillows.34

To save you some time, (and possibly money by preventing a bad purchase) Nick Robinson, creator of the website Sleep Like the Dead aggregated more than 21,000 consumer reviews from sites like Amazon and Overstock into a table that scores nine types of pillows in 21 categories.35

For example, if you wanted to find a pillow that online reviewers says reduces pain or is good for sleeping on your stomach, the table can point you to a category of pillow (say, a down alternative) and then towards a specific brand.


I already wrote about the importance of dimming lights and expelling gadgets from the bedroom. I’ll just add here that if you have problems with light at night (like a streetlamp shining in your window, or some other non-controllable factor) light-blocking curtains are a lifesaver. Insulated thermal panel curtains from Overstock get high scores by reviewers. My personal recommendation: stylish velvet light-blocking curtains from Target.

A light-blocking sleep mask is a cheaper, more portable option. Online reviewers like the Prime Effects sleep mask that has attached earplugs.


If you like to sleep with typical blankets, the ideal sleep temperature appears to be between 60.8 and 66.2 degrees at night. If you’re the rare person that sleeps naked with no covers, something like 86-89.6 degrees is better. And if you sleep with just a sheet over yourself, you’ll probably be best off somewhere in between.36

If you sleep with a partner, there’s always a chance that no amount of thermostat adjusting will make you both happy. One interesting option: regulating mattress temperature. The ChiliPad and the Outlast mattress pad both go over your existing mattress and use different technologies to adjust temperature for hot and cold sleepers.

If spending hundreds of dollars on a fancy mattress pad isn’t your idea of a good investment, hot sleepers could consider using a fan for a stream of cool air. And cold sleepers always have the option of more clothing or blankets.

The fastest ways to get to sleep

Now for the main event: falling and staying asleep.

The average amount of time it takes to fall asleep is 6.3 minutes, but anything less than 15 minutes is good.37If you’re still lying awake after that,  here are two interesting techniques I found.

Progressive relaxation. Basically, it’s going through your entire body, from your forehead to your toes, tensing each muscle one-by-one, then releasing that tension.38 There are countless  videos that will guide you through this process. Yoga teacher Jodie Tingle-Willis, says it’s important to find a video with a pleasing voice. “I might like an Australian accent, but it might drive you crazy,” she says.

One study found that progressive relaxation was very effective in helping people with multiple sclerosis get to sleep39 and another found that progressive relaxation can be as effective as Valium in reducing brain activity during a stressful state.40 Unfortunately, I didn’t find any tests of the effectiveness of progressive relaxation for sleep in people who weren’t suffering from chronic conditions.

The “cognitive shuffle.” We’ve all been there: maybe you’re worried about what you have to do tomorrow, or what you did today. All of the sudden, you feel like you’re stuck in an endless loop of thoughts. There’s an app that can help stop that loop—as long as you’re going to take your phone to bed despite some researchers’ advice not to. The idea behind mySleepButton is to take your mind off your worries by guiding you through a series of random images like, “a canoe, playing golf, holding a paper cup.”  (41) 41

Body position is one of the less-discussed aspects of sleep. Joseph De Koninck isa psychology professor at the University of Ottawa researches sleep and dreams. He says that younger adults tend to change position about 30 times per night. When he filmed people for two nights in a sleep lab, he found that “good sleepers,” or people who are normally satisfied with their sleep, changed position less than people who weren’t satisfied.

The good sleeper group also spent more time lying on their right side with their arms and legs both folded. Poor sleepers spent a lot of time on their back.42

Although none of the participants in his study had a sleep disorder, De Koninck says back sleeping is also associated with sleep apnea. If you’re healthy and don’t have any trouble sleeping, De Koninck says there’s no reason to change your sleep position. But if you do want to sleep on your back less, he mentioned devices like the Zzoma—a belt with a pillow attached to the back to make it more comfortable to rest on your side and less comfortable to lay on your back.

Interesting side note: another, more recent study found that right-side sleepers got better scores on the Pittsburgh Sleep Quality Index and had fewer nightmares than left-side sleepers.43

Focus on rest, not sleep. “I always advise people to never look at the alarm clock, never look at the phone. It doesn’t help to know what time it is. It doesn’t help to know how long you’ve been awake. It’s just going to make you stress out,” says Robin Haight. “Just know that your body is resting, even if you aren’t sleeping.”

In one study, participants were challenged to fall asleep as quickly as possible, with a monetary reward attached. But of course the challenge group ended up getting less and worse sleep than the control group, who simply went to sleep with no instructions.44

Sleep supplements. I can’t ignore supplements when writing about sleep. But, this is a HUGE topic. For the sake of not making this article a million words long, I stuck to over-the-counter supplements. This definitely isn’t an exhaustive list, but here are some I ran across, and briefly and what published research says about them:

  • Diphenhydramine, the active ingredient in Benadryl, can work for occasional trouble falling asleep. But its effectiveness wears off pretty quickly with repeated use.45
  • Same with doxylamine, the ingredient in Unisom.46
  • Melatonin supplements might help you fall asleep, but they’re not a surefire shot at a good night’s sleep.47 Oddly, one study found that melatonin found naturally in cherry juice was helpful for sleep.48
  • Valerian, an herb sold in capsule form, doesn’t really do much.49
  • Tryptophan, an amino acid, can be effective.50 Even small amounts can be effective, such as the levels found in foods like turkey and pumpkin seeds.51
  • Finally, a magnesium supplement can be effective if you have a deficiency52 but the effects have mostly been studied in adults over 50.53

My summary: this is only what some of the research says. There’s a lot more out there about all these substances. If you’re interested in one, do some more reading on your own.

Better sleep: how much is enough?

“If you always need an alarm clock to wake up, you’re probably not getting enough sleep.”

Once you’re asleep, how long should you stay there? 6.6 hours in bed is the norm, but that might not be enough. 25-34-year olds say they’d like to get 7.4 hours to function and feel best.54

Elizabeth Klerman, a professor at Harvard Medical School’s Division of Sleep Medicine, who’s studied sleep variation found that when given the opportunity to sleep more hours, people will do it. In one of her studies, people who reported a baseline of 6.1-10.3 hours of sleep per night slept an average of 4.9 hours more when they were allowed to. The participants with a higher baseline of sleep leveled off after a few days, but the people more towards the 6.1 end continued to sleep more hours. (51) Klerman says this suggests that a lot of people are walking around with a sleep debt and they don’t realize it.

Klerman’s advice: “If you always need an alarm clock to wake up, you’re probably not getting enough sleep.”

Waking Up

Oh, hey, it’s been 8 hours. Or 6. Or whatever. It’s time to get up!

Unless you got your magic number of sleep hours, you’re probably feeling groggy and maybe fumbling around as you start your morning routine. That feeling is called sleep inertia. It’s the time between the alarm going off and when you feel fully awake and it can last from a few minutes to a couple hours.55

The only way to not experience this feeling is to wake up naturally, with no alarm clock.56 Of course, if that’s not possible, an artificial dawn light might help. 18-36-year-olds who had trouble waking up at least 4 days a week, said the light helped them feel less sleepy and more active after using the light for 30 minutes before the alarm went off. 57

The Sleep Cycle app is something else you can try to cut down on that feeling of sleep inertia. You set the alarm on it for the time you want to wake up, say 7 a.m. It uses the accelerator on your phone to sense movement during the night. According to the product description, you move differently in every phase of sleep, so Sleep Cycle will use that movement to wake you up when you’re in the lightest phase of sleep at some point between 6:30 and 7.58

I didn’t find any studies that put Sleep Cycle to the test, but Fitbit data analyst Naveen Sinha, 29, says he relies on it. Tytus Wilson has also used the app since 2009. “I noticed that it was good at waking me up in that already restless time. I would just hear the ding and be ready to go,” he says.

Regardless of the type of alarm you use, try not to hit snooze. I didn’t find any peer-reviewed research that specifically says not to, but I did find these two solid arguments:

  • When you hit snooze, your body restarts the sleep cycle, making you more and more sleepy each time your alarm goes off59
  • If you’re snoozing for 20 to 30 minutes anyway, why not set y0ur alarm later and just get solid, uninterrupted sleep?60

So just get out of bed, already! That sounds easy until it’s actually time to do it, right? To really get yourself going in the morning, try one of these highly motivational alarm clocks. One forces you to stand up on your feet, one is a weight that makes you do 30 reps and another connects to your bank account, then makes a donation each time you hit snooze.61

What to do after a bad night’s sleep

Occasionally (well, hopefully occasionally), everyone has a night where they only get a few hours of sleep. Here’s what you can do to survive those sleep-deprived days.

Two obvious solutions are caffeine and naps. But which one works better?  Actually, they’re both about the same, according to one study that compared signs of afternoon sleepiness after a 20-minute nap or two cups of coffee containing 150 mg of caffeine. Measures of sleepiness went down a little, but not really that much. Then again, this study only tested participants who had slept normally the night before.62

After a night of sleep restriction (to 4.7 and 5 hours), two studies found that a 10-minute nap decreased feelings of sleepiness and improved cognitive performance.63 64 Another study showed that 100 mg of caffeine (in pill form) improved performance on a grammatical reasoning test and lessened feelings of sleepiness. Caffeine didn’t beat a placebo on a test of alertness and reaction time.65

If you’re worried about overall caffeine intake, even a placebo might help. Two groups of people in one study each had one cup of decaffeinated coffee. Researchers told one group that their coffee was caffeinated. The group who thought they’d consumed caffeine had quicker reaction times and fewer mistakes on performance tests.66

If you’re going to put your head down on your desk, or against the window of a bus and take that 10-minute nap, the Ostrich Pillow might help you out. It’s sort of like a pillow hood that goes down over your eyes. It allows your forehead or the side of your head to rest on a hard surface, and there are holes at the top for your hands during a desk nap. Another version, the Ostrich Pillow Light, is like a padded sweatband that wraps around your forehead and eyes.

Can’t nap or caffeinate? Try physical movement. Jodie Tingle-Willis, a yoga instructor in Louisville, Ky. recommends a few moves to wake yourself up. “Opening up the chest is really good, so you can take your hands behind you and grab the chair on either side and reach your heart up and forward and take some really nice, deep breaths in and out,” she says. She also recommends a chest-opening side stretch where you leave your left arm by your side, extend your right over your head, and bend to the right.

“A little less conventional is to take off your shoes and actually give yourself a little bit of a foot massage,” says Tingle-Willis. She says pounding gently on the sole of your foot can wake up nerve endings and bring energy into the body.

Michael Bonnet, a professor of neurology at Wright State University School of Medicine, recommends simply getting up and walking around to overcome sleepiness. But, he says the more-sleep deprived you are, the sooner the energizing effect wears off, and the more activity you’ll need.

Your next step: make sleep a priority

Almost every sleep researcher I talked to emphasized the importance of making sleep a priority. Eliza Van Reen, from Brown University emphasizes making a priority of going to bed at a certain time each night and keeping a regular sleep schedule. She says she knows you’ve probably heard that before, and that it’s easier said than done, but it works.

In this article, I didn’t even go into the importance of timing your sleep or understanding circadian rhythms. That stuff matters too, but the fact of the matter is that you probably won’t be successful at harnessing any of those techniques to improve sleep until you decide to make sleep a priority.

And, just like eating less junk food or making a workout pact, committing to sleeping better is not a promise to be made lightly. Getting good sleep is just about the most important step you can do to improving your health, productivity, and well, happiness. While we usually list our specific recommendations at the end of articles, I find it hard to make specific recommendations since sleep is something that everyone knows they need more of, yet we somehow can’t find the will to do it.

So I’ll end with a question.

How will you start sleeping better?


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Lymphoma Products

On the relationship between organochlorines and human cancer risk (Sources: Breast Cancer Research and Treatment 2002, Breast Cancer Research 2005). Risk of Non-Hodgkin’s lymphoma (NHL) associated with contemporary hair dye use varies by genetic polymorphisms; particularly, immunological genes, DNA repair genes, and genes involved in the metabolism of environmental exposures may influence individual susceptibility for NHL.

Below is a table with common genetic variants that modulate risk for lymphoma when exposed to benzenes and ogranochlorenes:

Table 1.







Immune-related genes















[2, 5]












[2, 5]



[2, 5]
















Genes that metabolize NHL-relevant environmental exposures












[9, 10]







DNA Repair Genes



































1.         Bi, X., et al., Genetic polymorphisms in IL10RA and TNF modify the association between blood transfusion and risk of non-Hodgkin lymphoma. Am J Hematol, 2012. 87(8): p. 766-9.

2.         Deng, Q., et al., Occupational solvent exposure, genetic variation in immune genes, and the risk for non-Hodgkin lymphoma. Eur J Cancer Prev, 2013. 22(1): p. 77-82.

3.         Skibola, C.F., et al., Tumor necrosis factor (TNF) and lymphotoxin-alpha (LTA) polymorphisms and risk of non-Hodgkin lymphoma in the InterLymph Consortium. Am J Epidemiol, 2010. 171(3): p. 267-76.

4..         Hosgood, H.D., 3rd, et al., A pooled analysis of three studies evaluating genetic variation in innate immunity genes and non-Hodgkin lymphoma risk. Br J Haematol, 2011. 152(6): p. 721-6.

5.         Lan, Q., et al., Cytokine polymorphisms in the Th1/Th2 pathway and susceptibility to non-Hodgkin lymphoma. Blood, 2006. 107(10): p. 4101-8.

6.         Hu, W., et al., Polymorphisms in pattern-recognition genes in the innate immunity system and risk of non-Hodgkin lymphoma. Environ Mol Mutagen, 2013. 54(1): p. 72-7.

7.         Shen, M., et al., Polymorphisms in integrin genes and lymphoma risk. Leuk Res, 2011. 35(7): p. 968-70.

8.         Ng, C.H., et al., Interaction between organochlorines and the AHR gene, and risk of non-Hodgkin lymphoma. Cancer Causes Control, 2010. 21(1): p. 11-22.

9.       Kilfoy, B.A., et al., Genetic polymorphisms in glutathione S-transferases and cytochrome P450s, tobacco smoking, and risk of non-Hodgkin lymphoma. Am J Hematol, 2009. 84(5): p. 279-82.

10.       Soucek, P., et al., Genetic polymorphisms of biotransformation enzymes in patients with Hodgkin’s and non-Hodgkin’s lymphomas. Int Arch Occup Environ Health, 2002. 75 Suppl: p. S86-92.

11.       Farawela, H., et al., The association between hepatitis C virus infection, genetic polymorphisms of oxidative stress genes and B-cell non-Hodgkin’s lymphoma risk in Egypt. Infect Genet Evol, 2012. 12(6): p. 1189-94.

12.       Shen, M., et al., Polymorphisms in DNA repair genes and risk of non-Hodgkin lymphoma among women in Connecticut. Hum Genet, 2006. 119(6): p. 659-68.

13.       Jiao, J., et al., Occupational solvent exposure, genetic variation of DNA repair genes, and the risk of non-Hodgkin’s lymphoma. Eur J Cancer Prev, 2012. 21(6): p. 580-4.

14.       Smedby, K.E., et al., Variation in DNA repair genes ERCC2, XRCC1, and XRCC3 and risk of follicular lymphoma. Cancer Epidemiol Biomarkers Prev, 2006. 15(2): p. 258-65.

Bottom line:

The studies indicate that, in general, exposure to one or more of the chemicals mentioned will increase your risk by about 50% if you are exposed to them for at least 20 years (not accounting for genetic risk). And if you have any one of the genetic variants (you are very unlikely to have more than one), and you are exposed to these chemicals, your risk is increased generally by 200% compared to normal genotype and unexposed people. The average occurrence of one of these genotypes is about 1 in 1,000.

So, chances are you are probably safe, but it wouldn’t hurt to avoid occupational exposure to these chemicals or using dangerous hair products. If you really want to make sure, you can test your genome to see if you have any of these SNPs.