Are you at your best when your friends and family are getting ready to go to sleep? Or do you jump out of bed when the sun has barely risen, bright and chipper and raring to go each morning? Ah, yes, such is the difference between night owls (also called evening types) and early birds (also called skylarks).
This characteristic, referred to as an individual’s chronotype, isn’t just something to marvel at or joke about. It’s something that can affect health, performance, and safety as we go about our daily activities.
In fact, according to a 2015 review paper in Current Sleep Medicine Report, numerous health problems are more frequently linked with night owls than with early birds—from diabetes, asthma, and insomnia to substance abuse and mood disorders (though these are associations only and do not prove causality). Other studies have noted differences in personality traits, with night owls, for instance, exhibiting more disinhibition, impulsivity, and sensation seeking and less persistence, which may help explain some of the health risks associated with this chronotype.
It’s not all bad news for night owls, however—some research has linked them with increased creativity.
Genetic factors partly, if not largely, predispose you to being a night owl or early bird, as suggested in a 2016 study in Nature Communications, in which nearly 90,000 people self-reported what they were and then had their DNA analyzed. The investigators found several genetic factors associated with “morningness” (the study did not address evening types).
But other factors can also influence whether you are a morning or evening type, including environmental circumstances (such as your work schedule, sleep habits, use of medications that can affect sleep, and cultural norms). Of course, many folks fall in the middle of the spectrum, being neither night owls nor skylarks.
Here’s a look at some unhealthy habits and potential medical problems linked with being a night owl (skylarks seem to largely be off the hook):
- Nutrition. A 2011 study in Obesity looked at the eating habits of 51 people in relationship to their habitual/preferred sleep-wake cycle. Forty-five percent could be classified as night owls because they went to sleep around 4 a.m. (give or take an hour or so) and awoke around 11 a.m.; the rest were “normal sleepers,” who went to bed around 12:30 a.m. (give or take 1.5 hours) and awoke at 8 a.m. All participants recorded their food intake over a week. Compared to normal sleepers, night owls were more likely to have a lower intake of fruits and vegetables and eat more sugar-sweetened sodas and fast food. They also slept one hour less a night, on average, and had a higher body mass index.
- Metabolic disorders. In a 2015 study in the Journal of Clinical Endocrinology and Metabolism from Korea, 1,620 middle-aged people filled out a questionnaire to assess if they were morning or evening types. Night owls, who were younger overall, had higher body fat (and lower lean body mass) and higher triglycerides (fats in the blood), compared with the early risers. Male night owls were more likely to develop diabetes than male early risers, while female night owls had more abdominal fat and an increased risk of metabolic syndrome than female morning types. These findings, the researchers explained, could be attributed to night owls having poorer-quality sleep and being more sedentary and more likely to consume more of their calories at night, all of which can adversely affect metabolic risk factors.
- Alcohol consumption. A 2013 study in Psychiatry Research: Neuroimaging reported that evening types had more alcohol dependence than morning types, possibly, the authors suggested, because they are more likely to engage in pleasure-seeking behavior. (They also had worse sleep quality.) In fact, brain imaging revealed that evening types had less activation in a particular part of the brain involved with rewards (in this case a monetary reward) than morning types did—and less activation was associated with more symptoms of alcohol dependence.
- Smoking. Night owls may be more likely to smoke, according to a study published in Addiction in 2010 that used data from a large population of twins in Finland who had been followed for 30 years. Evening types were also less likely to quit compared with early birds. It’s not clear what the connection is, but one explanation cited by the researchers is that people who stay up late may be more likely to frequent establishments where smokers gather. Or, as noted above, they may be more prone to addictions in general. The data were collected many years ago, however, when smoking prevalence was higher.
- Driving behavior. In a small 2014 study from Spain in Accident Analysis and Prevention, university students selected for being extreme morning or evening types drove in a simulator at both 8 a.m. and 8 p.m. (their optimal or non-optimal time of day). Early birds performed adequately regardless of the time of day, but night owls had reduced vigilance when they drove in the morning. Similarly, in a small study in Chronobiology International in 2014, evening types performed worse on a motorbike simulator in the morning (9 to 11 a.m.)—not following the speed limit, for instance, and having more trouble avoiding road hazards—compared to in the evening (6 to 8 p.m.). Morning types performed better in the morning—and just as well in the evening as evening types, suggesting that their driving performance was better overall. The results may be sleep related since the investigators found that the evening types were sleepier during the day and reported worse sleep quality compared with the morning people.
- Life outlook. In a 2012 paper in Emotion, people identified as early birds (both younger and older) reported a more positive life attitude than night owls. The authors speculate that this may be because their chronobiology allows them to more easily function and be in sync in a society that works mostly on a 9 to 5 schedule. Being out of sync, as the night owls are, may be related to what scientists call “social jet lag,” meaning that night owls find it difficult to wake up early and perform at their best during the day.
Bottom line: Being a night owl doesn’t automatically doom you to have bad habits or medical problems, but it might be one factor in your overall health and safety (for instance, if you are one, you should be especially careful when driving in the morning). Because much of one’s chronobiology is influenced by environmental factors, however, night owls may be able to change at least some of their patterns. They may, for instance, discipline themselves to change their sleep times or talk to their doctors about whether any medications they are taking might be affecting their sleep—though no matter how much they try, they may never become extreme skylarks. Something in the middle is perhaps a good place to aim for.
Not sure if you’re an early bird or night owl—or just want to see if you really are what you think you are? This 19-item multiple-choice questionnaire from the Center for Environmental Therapeutics will tell you where you fall on the chronotype continuum.