How much sleep you get a night may depend on where in your time zone you live, a new study suggests.
And that, in turn, may help to shape your overall health.
People that live on the wrong side of a time zone see more sun later into the evening, go to bed later, get less sleep, and may wind up with more health (and financial) problems.
Researchers at the University of Pittsburgh and the Universita della Svizzera in Italy found that people who live on the edge of a time zone where the sun sets latest are at the greatest risks for breast cancer, obesity, heart attack and diabetes.
People who live on the West side of each time zone go to bed later (dark blue), get less sleep, make less money, and suffer more diseases on average, as a map from the new study shows
Public health and sleep experts have been sounding the alarm that the US - and many countries the world over - are in a sleeplessness epidemic.
And being underslept is a known risk factor for health problems.
Even small changes like daylight savings time are associated with higher rates of heart attacks.
Similarly, we know that women rates of breast cancer are higher among women who do shift work.
Irregular work hours disrupt the circadian rhythms that dictate our biological clocks which contribute to the fluctuations of our hormones.
But the new study, published in the Journal of Health Economics, suggests that more minute differences in our days and schedules can shape our sleep schedules and health outcomes.
Moving westward, the sun sets later and later into the day, and even sets later within the time zone.
So within a single time zone, the sun sets a over an hour earlier on the east side than on the west side.
Sleep experts say that the constant presence of artificial lighting has made it far more difficult for the average person to sleep than it once was.
Even with all of that additional light pollution, the sun's presence in the sky still has powerful pull on us toward wakefulness or sleep.
The sun sets at a later time on the west side of each time zone (darker blues), as a map from the new study shows
Light triggers a chemical that travels to the brain and tells us what time it is and what it is