Scientists have discovered a gene variation that affects the human body clock so profoundly that it even predicts the time of day when an individual is most likely to die.
Researchers hope the findings could eventually be used to determine when heart or stroke patients should take medication to make it most effective, or when hospital patients should be monitored most closely.
The US team discovered the gene variation by accident when they were investigating the development of Parkinson’s and Alzheimer’s disease. They looked at the sleeping patterns of 1,200 healthy 65-year-olds who were also given annual neurological and psychiatric assessments.
Differences: Those with the AA or AG genotype died just before 11am on average, but those with the GG genotype tended to die at just before 6pm. They found a single molecule near a gene called ‘Period 1’ that had as its base either adenine (A) or guanine (G).
Type A is more common by a ratio of six to four, so because people have two sets of chromosomes, an individual has a 36 per cent chance of having two As, a 16 per cent chance of having two Gs, and a 48 per cent chance of an A and a G.
The findings, published in the Annals of Neurology, showed that those with a AA genotype tend naturally to wake up about an hour earlier than those with GG, and the AGs wake up almost exactly in the middle. They also showed that those with the AA or AG genotype died just before 11am on average, but those with the GG genotype tended to die at just before 6pm.
The study’s lead author Andrew Lim, from the Department of Neurology at Beth Israel Deaconess Medical Center in Boston, Massachusetts, said: ‘The internal “biological clock” regulates many aspects of human biology and behaviour. It also influences the timing of acute medical events like stroke and heart attack.’
Clifford Saper, chief of neurology at BIDMC, said: ‘So there is really a gene that predicts the time of day that you’ll die. Not the date, fortunately, but the time of day.’