What time of day you're likely to die

When you're most likely to die - November 22, 2012

Particularly when you're older, you're 14 percent more likely to die on your birthday than on any other day of the year. Particularly when you live in certain geographical areas, you're 13 percent more likely to die after getting paid. And particularly when you're human, you're more likely to die in the late morning -- around 11 a.m., specifically -- than at any other time during the day.

Yes. That last one comes from a new study, published in the Annals of Neurology, that identifies a common gene variant affecting circadian rhythms. And that variant, per study co-authors Andrew Lim and Clifford Saper, could also predict the time of day you will die.

But the circumstantial realities of old age change that, to a significant extent. "Social jet lag" -- the phenomenon through which our natural circadian rhythms are undermined by rigidly collective social schedules -- is less of a factor for people who aren't (generally) working and whose daily routines aren't (generally) governed by strict itineraries. It is less of a factor, in other words, for people who are relatively unreliant on technology. Retirees can sleep when they need to, wake when they want to, and generally obey the whims of their bodies much more readily than younger people can.

And that change in the way older people live also affects -- potentially, probabilistically -- the way they die. Because, just as circadian rhythms regulate things like preferred sleep periods and the time of peak cognitive performance, they also regulate the times during which we're most likely to experience an acute medical event like a stroke or heart attack. As Saper -- who is also the James Jackson Putnam Professor of Neurology and Neuroscience at Harvard Medical School, and also the chairman of the Beth Israel Deaconess Medical Center Department of Neurology -- explained to me over email, there is a "biological clock ticking in each of us."

So the technological freedom that comes with people's retirement can actually end up bringing a kind of cruel regularity to our deaths. What Saper and Lim realized through their research is that there seems to be one DNA sequence that determines, essentially, how each of us relates to time itself. And data analysis -- poring through 15 years' worth of sleep and death patterns collected from subjects in an unrelated sleep study -- helped them to make the realization.

What we found was a "single nucleotide polymorphism" or SNP where about 60% of chromosomes have an adenosine (A) and 40% have a guanine (G) in the DNA code. Because you have two copies of each chromosome (one from each parent), 36% of people have two A's (AA), 16% have two G's (GG), and 48% have one of each (AG). When we looked at a group of older but healthy people (all over 65, so mostly retired) we found that the AA's tend to wake up about 1 hr before the GG's, with the AG's in the middle.

What we think this means is that the AA's have somewhat higher amounts of a protein called Period1 in their cells, which we think causes their biological clock to run a bit faster. On a daily basis, what this means is that they would tend to get up a bit earlier each day. If this persisted (getting up earlier and earlier each day) they would soon be getting up in the middle of the night, and going to bed before dinnertime. This obviously would cut down on their ability to socialize with other people. So, we think that the AA's adjust their timing a bit each day, to stay at a "socially acceptably early" schedule, which is on average about an hour earlier than GG's.

But, then ... where does the 11 a.m. frequency -- and, for the GG group, a less-common 6 p.m. frequency -- fit into that framework? Why would we be more likely to die during those hours than at other times of the day? Genetics. Well, genetics and statistics. Again, Saper:

During the time when a person is dying, social calendars are much less important. So, we think that in that period, the individuals let their own biological clocks shift further from the external world, and the GG's drift further apart from the AA's. Interestingly, the AG's stay closer to the AA's, so perhaps just one A is enough to give a fairly early phenotype.

So you have a higher percentage of the population who carry the AA gene variant -- and, phenotypically, they're resembling the group with the AG variant. And that group is, due to all the factors Saper listed, more likely to die earlier in the day than other groups. Around, on average, 11 a.m.


By: kings World (738.70)

Tags: What time of day you\'re most likely to die

Location: United States

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