Death Has a Preference for Birthdays

This is a morbid post, but I have to do it!  The other night while perusing my feed reader, I saw this article from the Annals of Epidemiology.  (yeah, I have scientific journals in my feed reader – how else is a gal supposed to keep up with the medical literature for work! :-))

Ajdacic-Gross V, et al., Death has a preference for birthdaysdan analysis of death time series, Annals of Epidemiology (2012), doi:10.1016/j.annepidem.2012.04.016

I was ecstatic to see this because it presents research around something that I and my mother have talked about for years now.  As we look at the dates of death in our family trees, we seemed to have seen a pattern of people dying around their birthdays.  I was fascinated that a research group has set out to examine this on a large-scale basis. 

Here’s the overview of the research this team from the Institute of Social and Preventive Medicine in Zurich.  (you can look more closely at the article here)

Why did they do this research? Whether or not deaths occur more frequently around birthdays has been a controversial for 40 years. Some research on suicides has shown there is a relationship; some has shown there is not. Some research on cancer deaths has also had mixed results. The problem has been though that all of these studies have looked at small groups of people or had flaws in how the research was conducted.  This research team has access to a very large database of deaths, so wanted to study it and see if they observed a relationship. 

Who did they study? They used a Swiss database of computerized death records that spanned 1969-2008. Excluding infants less than 1  year of age and people who were born or died on February 29th, they had 2,380,997 deaths of all causes to examine.  Wow.

What did they find out?  When looking at all the deaths, they saw that there was a peak in the data set for deaths that occurred the same day as the person’s birthday.  The “peak” was statistically significant (e.g. higher than you would expect to occur on average).  Deaths from all cause occurred almost 14% more often on the person’s birthday than any other time of the year.  This was pretty much the case for both men and women. Taking suicides out of the equation and looking at only natural causes (because people make conscious decisions about when to commit suicide and may or may not purposefully do it around their birthday), the effect was still significant.  Deaths on the person’s birthday occurred 18.6% more often than other times of the year in cardiovascular disease, and in women with cerebrovascular disease 21.5% more often than any other time of the year.  In cancer, death occurred 10.8% more often on birthdays than any other time of the year.  Significant excesses of death on birthdays were also found for deaths from accidents (vehicular + falls) and endocrine diseases.

What does it mean? It means be careful around your birthday! Nah, seriously, it confirms what my mother and I have suspected for several years now.  Admittedly, I don’t think I’ve seen too many cases of death ON the birthday, but usually somewhere  AROUND the birthday.  Of course, all research has its limitations, so it will remain to be seen if others reproduce these findings.  For example, there are properties of the data set that may sway the results — when  the exact date of death is not known, it is not uncommon to put the 1st or 15th of the month.  If the the exact date of birth is not known, it is not uncommon to put the same date as the date of death.  In this study, the investigators were aware of these trends and did adjust for it. I find it fascinating nevertheless.  

To quote a line from Randy Quaid in Independence Day when the television is showing the alien invasions around the world:

Good God! I’ve been sayin’ it. I’ve been sayin’ it for ten **** years. Ain’t I been sayin’ it, Miguel? Yeah, I’ve been sayin’ it.

Minus the *expletive deleted,* that was precisely my reaction reading this study!  Case in point, my ancestor Rufus Tannahill McNair.  According to his headstone he was born June 11, 1823 and died June 11, 1910.  I was always a suspicious of those two dates; a little *too* convenient and I suspect it was a case as described above – they didn’t really know his birth date.  But, I do have plenty of other family members that did die around their birthdays. Hmm.. I should run a report in my database and see if I see any observable trends or if I’m just making it up.  

I’m in total MPH geekdom right now applying this epidemiological study to genealogy research. Kewl. :-)

 

8 thoughts on “Death Has a Preference for Birthdays

  1. Thank you for the study. Over two million data points should give some meaningful statistics. What would be more meaningful however, was if we knew the rest of the statistical information: what was the characteristics of the distribution (“Gaussian or Normal, skewed, kurtosis, bi-model or other?), what was the standard distribution, probable error, etc.). Can you provide those?

  2. Hi Jerry, very good points to raise! I do not know enough about the modelling techniques the authors employed to understand it’s assumptions surrounding data distribution. They used Box-Jenkins modeling as this was a time-series study. Perhaps knowing that will help?

  3. In my family, I often note that a widow/widower died within the same month (any year) as the spouse had died. For example, if first died on 23 August 1965, the second might die between 9 Aug and 6 Sept (1966+)

  4. Yes! I’ve noticed the same thing. I’ve also noticed that dates repeat through the generations. I’ve always thought I noticed it just because I notice it – you know like you just bought a dog and so you notice dogs and then it seems like everyone has dogs.

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