If you’re a morning person, you feel refreshed and ready to go in the early hours of the day and as the hours wear on, you can feel your energy gradually leave your body. You would much rather go to bed early and be ready to enjoy the rising of the sun over the horizon than take in the night lights. Whether it’s an 8 am meeting, a 5:45 spin class, or the chance to cook a hot breakfast before your kids need to catch the 7:15 am bus, you’re ready well ahead of time. The evening people or night owls who are forced to get up early seem to find your perkiness annoying, but you reason that it’s their problem, not yours. Being a morning person strikes you as ideal, because you will get more out of your day than those who don’t come to life until the sun sets.
As it turns out, your belief in the advantages of early rising is supported by the most recent research on chronotype, the formal term for morningness-eveningness. However, this research also suggests that you might regard more sympathetically those night owls who don’t share your zeal for the morning. According to Altug Didikoglu and colleagues, of the University of Manchester (UK), chronotype has a strong genetic basis. Surprisingly, you can also be influenced by the season in which you were born; the longer the days following your birth, the more likely it is you’ll be a morning person. If you were born in the summer in the northern hemisphere, then, this could account for your bright-eyed readiness to start your days now that you’re an adult.
According to Didikoglu et al., your preference for getting up early may actually benefit your health. As they note, “eveningness has been associated with affective disorders, cardiovascular disease, and metabolic health” (p. 2). Part of the reason for the poorer health of the night owls is that the late nights they enjoy so much are times when people are more likely to indulge in the bad habits of drinking, smoking, and late night snacking. Previous research suggested that these bad habits catch up with the night owls, who die at younger ages than the larks, but the data were incomplete.
The University of Manchester researchers were able to overcome the limitations of previous research by drawing on data from a large cohort of adults (6,375) who joined a longitudinal project begun in 1983. Didikoglu and his fellow researchers were able to track, over time, the relationships among chronotype, preferred wake and sleep times, longevity, and mental and physical health. Other measures included meal habits, clinical health data (body measurements and lab tests), demographic data, subjective health ratings and responses to measures of chronotype, depression, and personality. The authors also had data on the longevity of their participants. Clearly, the British team had considerable resources at its disposal to tease apart the complex interweaving of chronotype, daily health habits, and psychological well-being. The researchers could even investigate that time-of-birth effect on chronotype and then determine its effect on the key outcome measures.
Not all participants provided all data over the three decades of study, but the statistical model used by the authors allowed them to correct for missing data in the analyses of change over time. The first set of findings pertained to age and sleep patterns and, as expected, older participants showed a shift toward earlier bedtimes; however, there was no change over time in the hour of awakening. In general, people liked to stay up later and wake up earlier in the summer months. As you might expect, early chronotypes also ate their breakfast at 7:00 am but the late nighters struggled into the kitchen at about 8:30. The late chronotypes did, however, seem to have better social lives as they spent more time socializing and entertaining.
Now onto the question of health. Every indication supported the idea that early chronotypes are healthier than their late-rising counterparts: self-ratings of health, smoking, number of medications, alcohol use patterns, exercise habits, quality of sleep, and even just getting around. In terms of actual health indicators, evening types were at higher risk of hypertension and had higher scores on a measure of metabolic health that took cholesterol and obesity into account.
If the evening types are unhealthier, does this mean they die at younger ages? From mortality data spanning the 35 years of the study, the answer appears to be yes. It’s not the amount of time spent sleeping that predicted longevity, but simply whether people were early or late chronotypes. As the authors concluded, after controlling for everything else, “At the end of the studied period, 86.1% of the individuals in the evening-type cluster had died while the observed rate of death in the morning-type cluster was 77.1%” (p. 10). In a way, it’s frightening to think that the one variable in your life over which you have absolutely no control, namely your birthday, can predict the age at which you die. Add to this the genetic component which, again, you have no control over, and it can be daunting to contemplate the forces at work in determining your health and longevity.
You might cheer yourself up, if you didn’t have the good luck to become an early type, by thinking that you’ll become more of a morning type as you get older. Unfortunately, the Manchester study data suggest that people don’t really change from evening to morning types as they get older. Although older evening type participants felt they were shifting toward earlier wake time preferences, the actual sleep data did not confirm this. The only good news, if you are an evening type, is that your likelihood of being depressed is no higher than if you’re a morning type. People at both extremes of the chronotype scale experienced more depressive symptoms than those in the middle.
To sum up, taking into account both your sleep-wake preferences and your actual sleep-wake times can provide you with important information that you can use to regulate your health. You may be disadvantaged when it comes to the pre-programmed sleep determinants of how long you live, but you don’t have to be fated to an early death. Use this news to renew your own vows to improve your health habits, and you will reap the benefits that would otherwise only go to those who rise to greet the morning sun.