Marriage and Health Part 2: Does Poor Sleep Lead to More Conflict?

You get home from a long day of work, eager to lay down for a quick nap; a nap that will help you recover from a bad night of sleep.  As you get home, you start making your way to the couch to enter dream world, but your partner stops you and tells you to walk the dog because it’s your turn.  You contend that you want to sleep first, you’ll do it later, the dog can wait 30 minutes, and that they can do it.  You’re tired and irritable so you angrily proclaim that you’ll do it later, and before you know it…you’re fighting.

This simple example shows how poor sleep can lead to more relationship conflict.  You may be thinking that this seems obvious, and that psychologists have already established this.  Surprisingly, there have only been a handful of studies looking at how sleep influences relationship functioning.  As my primary research interest here at NDSU is sleep in the marital context, I find this a very exciting and important area.  So why does it happen?  What does the science behind this say?  This post will answer these questions.

In many of my previous posts, I’ve explained how sleep is important for physical and emotional health.  Well, it’s also very important for a number of cognitive processes. For example, poor sleep has been associated with decreases in emotional regulation, problem solving, empathy, and emotional recognition.  On top of this, it also increases negative affect and anger.  All of these are BAD for relationship communication and functioning.  If you’re in a relationship, you know how important communication is.  When a problem arises, you need to effectively express your own concerns, recognize what/how your partner is thinking, and strategize an agreeable resolution.  If your cognitive functioning is limited, it increases risk for conflict.

Let’s go back to the example from the first paragraph.  What if you weren’t sleep deprived? You likely would have approached this situation differently.  Maybe you would have noticed that your partner was also fatigued (your own restless sleep can negatively impact their sleep) and perhaps in a bad mood.  Instead of bluntly saying you’ll walk the dog later, you could effectively communicate how you feel and settle on a neutral agreement.  There are a number of different ways this scenario can play out depending on your cognitive resources.

Psychologists have recently begun empirically testing these ideas.  However, much of the current literature has focused on sleep disorders and how they affect relationship functioning.  For example, how snoring, sleep apnea, and insomnia affect your relationship (hint: it’s not good).  What is missing is how day to day sleep in non-disordered couples affect their functioning.  Fortunately, these ideas are finding their way into the field.

Gordon and Chen (2014) carried out two studies testing these concepts.  In study one, participants recorded their sleep quality and relationship conflict over a two-week period.  Using advanced statistics, they found that poor sleep independently led to more conflict the following day.  This type of statistical test is important because it shows the direction of the relationship.

Study 2 found similar results.  Participants came into the lab and, separate from one another, recorded their sleep quality and top sources of conflict.  They were then placed into the same room and were asked to discuss these sources of conflict. Researchers measured their affect, empathy, and conflict resolution.  Couples who had poorer sleep the previous night had lower levels of positive affect, less empathy towards their partner, and had lower conflict resolution.

These findings are a good first step in this new direction.  It tells us that sleep may in fact impact certain aspects of relationships.  This matters because we cannot just say that poor sleep impairs functioning; we need to know why this happens.  But why is it important to learn more about what generates conflict? Conflict is not only bad for relationship outcomes (i.e. divorce) but it is also detrimental to physical health.  In the next post for this series, I will go into more detail as to how conflict influences health.



Gordon, A. M., & Chen, S. (2014). The Role of Sleep in Interpersonal Conflict Do Sleepless Nights Mean Worse Fights?. Social Psychological and Personality Science, 5(2), 168-175.



Sleep Recommendations For Children

I wanted to write a very quick, yet important post while I’m home on vacation.  This topic may not seem incredibly important, but it serves as an important building block for lifelong health.  Growing up, my parents always tried to instill healthy habits such as brushing my teeth, staying active, and many others.  One under looked health habit in children is sleep.  Sleep needs vary across the lifespan, and many may wonder just how much sleep is needed from birth throughout the teenage years.

For the first time, the American Academy of Sleep Medicine has released their recommendations. These come from a yearlong project completed by 13 of the nation’s top sleep experts.  Here they are below:

4-12 months old: 12-16 hours per 24-hour period (including naps)

1-2 years old: 11-14 hours per 24-hour period (including naps)

3-5 years old: 10-13 hours per 24-hour period (including naps)

6-12 years old: 9-12 hours per 24-hour period

13-18 years old: 8-10 hours per 24-hour period


Healthy sleep is more than just getting the right number of hours though.  In future posts I will talk more about sleep health in infants and children!

Is Fitbit’s New Feature Fit For Healthy Sleep?

I want to start this post by saying that I am a fan and avid user of Fitbit. For my personal use, I have had both the Fitbit Charge HR and Fitbit Blaze, and have been a member for over a year. We also have a large inventory of Fitbits in our lab that we use for research. Fitbits are great in helping motivate people to live more active lives. I’m not alone in thinking this. As of August 2015, Fitbit had 9.5 million active users, with a total of 19 million registered users. All of this being said, I fear that this new feature may encourage poor sleep habits.

In case you missed it, Fitbit recently implemented a new feature that will set a sleep schedule for you that will help optimize your sleep. Here’s how it works. It averages your total sleep time, wake up time, and bedtime over the last month and using this information makes a recommendation for you to set a rigid schedule. I played around with mine, and it told me that averaged about 8 hours of sleep, like to go to sleep around 11:00pm, and wake up at 7:30am. Once this schedule is set up, it tells me to start getting ready for bed at 10:30pm and sets an alarm for 7:30am. Essentially, Fitbit is trying to motivate me to stick to a strict sleep schedule.

At first glance this seems great, right? As we know, sleep is important for health. So, if their app is helping to optimize our sleep, this should in turn make us healthier? This is a great idea! There is one problem though. This rationale does not completely align with the current sleep literature.

Sleep timing regularity is important for our sleep and physical health because it synchronizes our physiological sleep drive and our circadian rhythms1. Having more sleep variability is associated with more sleep problems and daytime fatigue2. So yes, regularity is important. But…the current sleep medicine therapies only target regularity for wake up times3. This contradicts some popular media sleep hygiene recommendations that propose regularity for both bed and wake time (I’m guessing this is what Fitbit based their app feature off of).

So why do sleep medicine therapies (i.e. Cognitive Behavioral Therapy for Insomnia) only target wake up times? The answer is simple. You should only try to sleep when you’re tired! Imagine yourself in this scenario. You fear that you are suffering from insomnia; you are having trouble falling and maintaining sleep and are struggling with bad daytime fatigue. Your therapist suggests setting a rigid sleep schedule for both your bedtime and wake time (let’s say 11:00pm and 8:00am). So the following night you try to implement this. You start getting ready for bed around 10:30 and get into bed at 11:00. But then you realize you aren’t tired! What then? You’re tossing and turning in bed, worrying that the longer you stay awake, the closer you get to your scheduled wake up time. Then you worry some more that you won’t fall asleep, and you worry some more. See this potentially disastrous cycle?

Each day is different, and you may not be tired at the same time every night.  Trying to sleep when you’re not tired may not only buffer treatment effects, but could also lead to worse sleep.  Due to this, targeting only wake up times may be efficacious and does not have as much potential to disrupt sleep. Trying to sleep when you’re not tired is also a poor sleep habit, because over time it associates your bed as a place where you cannot sleep (click here for more information).

In sum, I believe that this new feature by Fitbit is misleading and may potentially create unhealthy sleep habits. However, the current literature on this topic still needs A LOT more work. My lab has a few ongoing projects that will hopefully shed some light on this topic, so stay tuned in the next few years for updates on sleep schedule regularity!


  1. Dijk, D. J., & Czeisler, C. A. (1995). Contribution of the circadian pacemaker and the sleep homeostat to sleep propensity, sleep structure, electroencephalographic slow waves, and sleep spindle activity in humans. The Journal of neuroscience, 15(5), 3526-3538.
  2. Dijk, D. J., & Lockley, S. W. (2002). Invited Review: Integration of human sleep-wake regulation and circadian rhythmicity. Journal of applied physiology, 92(2), 852-862.2. Dijk, D. J., & Lockley, S. W. (2002). Invited Review: Integration of human sleep-wake regulation and circadian rhythmicity. Journal of applied physiology, 92(2), 852-862.
  3. Morin, C. M. (2011). Psychological and behavioral treatments for insomnia I: approaches and efficacy. In Principles and practice of sleep medicine (pp. 866-883). Elsevier Saunders, St. Louis, MO.

Restless Leg Syndrome: A Mysterious Sleep Disorder

From sleep paralysis to exploding head syndrome, there are a number of very strange sleep disorders. Perhaps one of the most mysterious though is restless leg syndrome (RLS). Its mystique is exacerbated by fact that it affects up to 15% of the population, and we do not know its exact causes. What exactly is RLS? This week’s post takes a look at the profile of RLS, its deleterious effects, potential causes, and treatments.

RLS is characterized by tingly sensations in the lower legs, often between the knees and ankles. The sensations occur when an individual is still for any length of time and are relieved by getting up and moving around. These creepy crawly feelings can last for hours, often forcing people to continuously move late into the night. Specific leg movements may include jerky movements of the legs and flexion of the hips, knees, ankles, and toes (click here for a video of RLS symptoms).

RLS generally develops during one’s 40’s or 50’s but can develop at much younger age as well (RLS is common in children diagnosed with ADHD). While sleep researchers have a firm grasp on the clinical features of RLS, its causes are still unclear. One belief is that it is a genetic disorder, and you are five times as likely to develop RLS if a first degree relative is diagnosed (for those interested in genetics, the ME1S1 gene is believed to be the leading genetic risk factor).

Iron deficiency is also a proposed risk factor. For example, in several case studies of subjects with anemia, RLS was reported. Further, following intravenous iron therapy, RLS symptomology not only improved, but was eradicated. Similarly, pregnancy is a major risk factor for RLS, perhaps due to the deficiency of iron during pregnancy.

The causes of RLS remain opaque. Because of this, treatment is also difficult. In patients with moderate to severe RLS, drug therapy is needed (i.e. dopaminergic drugs, opioids, benzodiazepines, iron injections). In less severe cases, daytime exercise and massaging of the legs have been shown to help.

Taking all of his into consideration, it is clear that RLS is a dire disorder. Outside of its harmful effects on sleep, there are also other consequences commonly associated with RLS. The continuous movement of the limbs is associated with increased autonomic activity, which increases risk for high blood pressure and cardiovascular disease. Individuals afflicted with this are also at higher risks for depression, social withdrawal, headaches, and daytime fatigue.

RLS is a mysterious and harmful sleep disorder. If you think that you may have RLS, consult with your primary care physician or a sleep specialist.


Ekbom, K., & Ulfberg, J. (2009). Restless legs syndrome. Journal of internal medicine, 266(5), 419-431.

Circadian Rhythms Strongly Influence Monday Night Football In The NFL

In the human brain, the hypothalamus houses a small region called the suprachiasmatic nuclei, which is responsible for our circadian rhythms. Our most notable circadian rhythm is our sleep-wake cycle, but there are also less obvious ones. Perhaps one of the most influential is our alteration of arousal throughout the day. When we are most lively (it peaks in the morning and early evening), physical and mental performance is at its highest. Conversely, they are at their lowest when you get closer to midnight.

Previous studies have shown us that our peak athletic performance is in the late afternoon, and athlete’s subjective reports corroborate these findings. Given this, it would make sense then that Monday Night Football games in the NFL do not facilitate peak performance, since our rhythms are continuously dipping during this time of the night. This may be true, but is it for every team?

Sleep scientists at Stanford answered this question with a retrospective study of Monday Night Games over a 25 year period. They hypothesized that west coast football teams would have an innate advantage over east coast teams when playing in the east coast (e.g. the San Francisco 49’s playing at the Detroit Lions). This prediction was based solely on circadian preferences. On Monday Night Football games being played on the east coast, both teams are playing at 9:00pm, but the west coast team is essentially playing at 6:00pm, which is very close to the time of day that allows peak performance.

Amazingly, this is exactly what they found; west coast teams won more often and by more points per game than the east coast teams. Over this 25 year period, west coast teams won 59.3% of their home games, and 71% of Monday Night Football home games. East coast teams won 56.5% of their home games, but only 48.3% of their Monday Night Football home games. When an east coast team plays a team in any other time zone, their win percentage jumps up to 67.5%.   Similarly, when a west coast team plays a non-east coast team, their winning percentage drops to 58.1%. These numbers tell us that when a west coast team plays on Monday night versus an east coast team, whether it be home or away, their circadian rhythm gives them a strong advantage.

What makes this finding even more incredible is that these analyses took the point spread into account, which thwarts the argument that west coast teams just might be better than east coast teams (the point spread is a metric which includes a number of factors that would place one team at an advantage over the other: skill, injuries, etc.).

Since this study, NFL teams have taken their circadian rhythms into serious consideration when preparing for their next game; teams will often hire sleep specialists to coordinate travel plans for away games. In my own personal opinion, this is one of the main reasons why there will never be a permanent NFL team in London. It would offer a distinct home field advantage for the London team, and will confer a serious disadvantage for away games due to their constant travel across the pond. If the NFL wants an team in London, they must take their player’s biological rhythms into consideration.


Smith, R. S., Guilleminault, C., & Efron, B. (1997). Sports, sleep, and Circadian rhythms Orcadian rhythms and enhanced athletic performance in the National football league. Sleep, 20(5), 362-365.

Later Weekday Bedtimes May Be an Independent Risk Factor for Obesity

In one of my previous posts I detailed how eating close to bedtime impairs your sleep quality, which may confer risk for obesity. Similarly, this week we look at a recent finding that having a consistent later bedtime can lead to increases in BMI over time.

It is important to view obesity from a developmental perspective; in many cases obesity starts in childhood and can progress into adulthood.  In fact, the current childhood obesity rates are alarming.  In 2012 data, 17% of children 2-19 were obese. While this number is down from recent years, this is still far too high.

 When looking at this data, one of the questions is always “why is this happening?’  One potential explanation may simply be how late you decide to go to bed.  A 2015 study by Asarnow and colleagues found that no matter how long participants slept, later weekday bedtimes were associated with increases in BMI over time.  This study not only controlled for sleep duration, but also fast food consumption and exercise frequency.  So, regardless of how long you long you sleep, how infrequently you exercise, or how much fast food you consume, going to bed at a later time can be a risk factor for obesity.

 This is pretty amazing.  This could also help explain why obesity rates in children are so high.  Surveys have shown that around 40% of teens prefer later bedtimes, and onset of puberty delays a night owl’s sleep period even more.  In another study of high school upperclassmen, 60% of them stated that they also prefer staying up late.

 But why is this happening?  Late bedtimes, which can desynchronize your internal and external biological clocks, have been shown to lead to metabolic disturbances such as disturbed glucose and insulin metabolism (my next post will explain how poor sleep is a risk factor for Type 2 Diabetes).  These disturbed process are then what contribute to the physiological changes that lead to increases in BMI.

This has important implications for public health and intervention research.  If future studies are able to replicate this effect, bed times can be a target for prevention and treatment for obesity. This is a very hot topic right now, and it will be exciting to see what comes out in the following years!

Asarnow, L. D., McGlinchey, E., & Harvey, A. G. (2015). Evidence for a Possible Link between Bedtime and Change in Body Mass Index. Sleep.

For statistics on childhood obesity:

Using eReaders Near Bedtime Impairs Sleep Quality

Sleep science has produced considerable evidence showing that exposure to light before bedtime is bad for sleep. This light can come from computers, phones, night-lights, streetlights outside, and other various sources. One unexpected source has become increasingly common; electronic readers. Light emitting eReaders are exceptionally convenient, in that you can store your whole library of books in it. Moreover, you can now surf the web and do other related activities on them. As many people like to read before bed, one must wonder if eReaders affect your sleep. In a recent study, Chang and colleagues (2015) tackled this question.

Before getting to the results of that study, let’s go over some basic sleep physiology. Our body has what is called a circadian clock, which gives us our daily rhythms of arousal and sleep drive. This clock is driven by both biological and environmental factors. Biologically speaking, our propensity for sleep is driven by melatonin. When our internal clock tells us it’s time for bed, it starts to release melatonin, which makes us sleepy and facilitates sleep onset.

Our social environment serves as our external clock, and also plays a vital role. We rely on specific cues that tell our body that it is time for sleep. Light is the most influential of these factors. Light delays the sleep process by its suppressing effects on melatonin. To get the best quality sleep, our internal and external clocks need to be in synch with one another. When this does not happen, it can lead to sleep difficulty.

So how do eReaders affect sleep? Researchers brought in 12 young, healthy adults into a sleep lab, and had them complete two consecutive conditions of a single study (each participant completed both conditions). This is a within-subjects design, which allows us to compare each of the two conditions within the same participant. Doing this really allows researchers to compare the two conditions of a study. In the first condition, participants spent five consecutive nights in the lab, and read an eReader in a dim room about four hours before bedtime. The second condition consisted of five more nights, but they read a hard copy book. Half of the participants completed the eReader condition first, and the other half completed the hard copy first.

They found that when using the eReader before bed, participants had a whole lot of problems. Their melatonin levels were suppressed by more than 50%, delaying their internal clock by about 90 minutes. Using the eReader lead to participants taking 10 minutes longer to fall sleep, and they also spent less time in REM during sleep. Using the eReader also lead to greater self reported pre-sleep arousal and decreased alertness the following morning.

This study shows that eReaders not only delay your propensity for sleep, but it also decreases sleep quality, leading to decreases in daytime arousal. In a previous post I’ve detailed all the poor health effects of insufficient sleep, but this study adds to that. Melatonin is important in more ways than making sleep come easier to us. Melatonin suppression has been associated with increased risk for breast cancer, colorectal cancer, prostate cancer, and a number of sleep disorders. When approaching bedtime, we should consider that various light sources that may be influencing not only our sleep, but also our health.

Chang, A. M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232-1237.