The settings for a person’s biological clock might provide clues to when, during the day, he or she will be more active. What’s more, these same settings could be linked to what time of day a person might die, a new study finds.
Understanding the biological basis of these built-in, or circadian, clocks “could lead to products that eventually allow us to shift the clock forwards or backwards,” says Philip De Jager, a neurologist with Harvard Medical School in Boston. He and his colleagues describe their work online April 26 in Annals of Neurology.
Being able to alter these clocks could prove useful for shift workers, such as pilots, who might face trouble working against their intrinsic daily rhythms, De Jager adds. And patients can be better cared for if doctors know what times of day are most critical.
Previously, scientists have shown that many genes are involved in regulating people’s inherent daily wake and sleep patterns. Disruptions to this natural circadian rhythm are often linked to serious health conditions, including diabetes.
In the new work, De Jager’s team took a close look at common subtle tweaks that occur in a circadian clock-regulating gene called PER1. By mostly focusing on DNA samples collected from a group of 537 older adults of European ancestry, the team found that there were three different variations of PER1. The researchers also found these variations in another smaller group of 38 people between 18 and 72 years old.
The specific variations were associated with certain times of the day when a person was most active. Peak activity levels differed by about an hour between the groups of individuals with particular variations.
The variations also appeared to be linked to a person’s time of death, scientists found after analyzing a larger sample of 687 older people. Patients with one kind of tweak to PER1 tended to die earlier in the day, at about 11 a.m., while others with a different tweak to the gene passed away hours later, at about 6 p.m.
Data analyzed in the study was gathered for other projects, and the researchers don’t know how these patients died.
Still, deaths linked to certain times of the day are not unusual, says Satchidananda Panda at the Salk Institute for Biological Studies in San Diego. Because the heart beats more rapidly right before a person wakes up, patients with heart conditions are most vulnerable earlier in the day, as they rustle out of bed.
So PER1 variations “might be weakening one or multiple organs that need to crank up at certain times of the day. That’s why you might see these deaths,” explains Panda.
But further work is needed, he says, to look at the exact role of these gene variations and whether they are associated with any medical conditions.