Sleep scientist Matthew Walker has observed that “human beings are the only species that deliberately deprive themselves of sleep for no apparent gain.” We stay up late to watch our favorite TV shows. We wake up early to get to work or school on time. And twice a year we change our clocks, to the bewilderment of our circadian rhythms.
We also set up conflicts between our natural and social clocks in other ways, a fact underscored in research published in the Journal of Health Economics. It turns out that living on the wrong side of a time zone’s boundary can have negative consequences on a person’s health and wallet.
The culprit? More natural light in the evening hours.
To understand the study, co-authored by Osea Giuntella of the University of Pittsburgh and Fabrizio Mazzonna of the Universita della Svizzera Italiana, it is important to understand how time zones affect local sunset times. Traveling east to west, sunrise and sunset times get later.
Sunset is a powerful biological trigger: The fading of natural light causes the body to release melatonin, a hormone that induces drowsiness. As a result, people on the eastern side of a time zone, where the sun sets earlier, tend to go to bed earlier than those on the western side — by 19 minutes, on average.
The problem for folks who go to bed later is that they generally cannot make up lost sleep on the back end: Work and school have set start times.
Roughly speaking, 19 minutes a day translates to 115 hours of lost sleep per year. People on the late side of sunset across U.S. time zones were 11% more likely, on average, to be overweight and 21% more likely to be obese. Diabetes was more prevalent, and the risk of heart attack increased by 19%.