Your genetic code may not be able to predict how you will die, but researchers have found that it may tell you what time it will happen.

A Harvard research group followed a large number of individuals’ circadian rhythms—the body’s internal clock that helps to determine sleep cycles—and found that one particular mechanism in this process was directly associated with the time of day a person dies.

According to Philip De Jager, an associate professor and researcher at Harvard Medical School who helped conduct the study, he and his colleagues collected the data of 500 subjects ages 65 and up fitted with an actograph, a device worn like a wristwatch that tracks the movements of the arm to determine where a person is in the circadian cycle. He said data gathered from the actographs were then compared to each individual’s DNA to determine if certain genes correlated with each subject’s

biological clock.

“Since the study involved an older age group, we had a large number of people in the study die,” said Andrew Lim, a clinical fellow at Harvard Medical School and lead author of the study. “So we looked at the gene variants and compared those to the time of death.”

According to Lim, who is also a scientist at Sunnybrook Health Sciences Centre in Toronto, the researchers recognized a gene variant in each individual that showed different configurations of DNA nucleotides, which determined whether a person was an early bird, a late riser or in between. He said the nucleotide adenine (A) was linked to early risers and guanine (G) to late risers. Lim said 36 percent of people with a variant of A-A were more likely to go to sleep and wake up an hour earlier than the 16 percent of people with a G-G variant. The remaining subjects had a dual copy A-G variant and would sleep and wake somewhere in between the other two, he said.

When the researchers analyzed data from participants who had died, they found that people with the A-A combination died just before 11 a.m., and the group with the G-G combo died just after 6 p.m., Lim said.

“As for a medical applicative, the provocative finding that this gene is associated with the time of death is important,” De Jager said. “We know that things like epilepsy and heart failure are strongly associated with circadian rhythms, so we can highlight times of day that a hospital patient may need to be more closely monitored.”

Lim said that when examining the deceased subjects’ gene variants, the researchers were unable to determine the cause of death, which may add an air of eeriness to the findings, he said.

“We didn’t have the information on the cause of death for all of the patients in the study,” Lim said. “But what we do know is that 97 percent of the deaths were related to some form of medical cause.”