A statistical phenomenon known as the Birthday Effect has proven that an individual’s likelihood of death appears to increase leading up to, and during, their birthday. Further evidence has also suggested that this phenomenon is not exclusively associated with birthdays, but also has been seen around cultural or religious holidays, including Passover.
How was the Birthday Effect discovered?
Several theories have been explored as a way in which to explain the birthday effect, with the first large-scale study having been carried out in 1990 by Dr. David P. Phillips, who was a sociology professor at the University of California in San Diego.
The study examined 2,745,149 natural deaths that occurred from 1969 to 1990, comparing the date of birth to the date of death in order to assess whether or not there was a correlation between the two. They discovered that for women, there was a 3% increase in deaths in the week after a birthday, with a slight decrease leading up to the birthday. For men, however, deaths peaked – rather than decreased – ahead of birthdays.
Again in 2012, a similar study was made, this time in Switzerland. The resulting data showed that 13.8% more people over the age of 60 died on their own birthday compared to any other day of the year.
Similarly, a 2015 study used records from the US Social Security Administration in order to examine the data of 25 million people who died between 1998 and 2011. It found that overall, 6.7% more people are expected to die on their birthday rather than any other day. It also found that younger people have greater average excess death rates on birthdays, reaching as high as over 25% for people aged 20-29.
Not just birthdays
Although it is known as the Birthday Effect, the phenomenon occurs at other times of the year as well, most notably around significant cultural or religious holidays.
An additional study led by Phillips examined the number of people who died in emergency settings – or were declared dead upon arrival – from December 25-January 7 each year 1973 through 2001.
The researchers examined the records for 53 million deaths from natural causes – excluding suicides, homicides and accidents – and then compared their findings with the number of deaths that typically occur in a similar length of time at other points of the year.
They found that death rates from heart attacks, strokes and other natural causes spiked during the holiday season, with holiday death rates reaching as much as 4.4% higher than expected. The study’s findings indicate that there are 4.65% more heart-related deaths and 4.99% more deaths related to other natural causes than there would be in the same length of time at a different point in the year.
Not satisfied with having proven the connection between birthdays, Christmas, and death, Phillips set out to examine whether or not the same phenomenon was present in other cultures, namely Judaism.
Along with fellow sociologist Elliot King, Phillips discovered that when examining the time period surrounding the Passover holiday, Jewish mortality rates fell in the weeks preceding the first night, but then spiked again immediately after.
Of the 1,919 Jewish death records they examined across 17 different two-week periods before and after the first night of Passover, there were a total of 8.1% more deaths during the week following Passover than the week before.
The Passover Effect, as it was dubbed by the researchers, was also proven to be significantly stronger when the first night of the holiday fell on a weekend. They observed a 61.4% increase in men’s deaths after Passover fell on a weekend, compared to a 13.7% rise when it did not.
What causes the Birthday Effect?
With the data from multiple studies now seemingly confirming the existence of this phenomenon and its impact on various holidays, researchers set out to understand the cause.
External causes
One possible explanation is that birthday celebrations and holiday events are often associated with large amounts of alcohol consumption. When too much is consumed there is an increased risk of death, whether through alcohol poisoning, drunk driving or other accidents. Excessive alcohol consumption can also exacerbate preexisting conditions or increase suicidal tendencies, thereby driving up the death rates around these periods of time.
Another possible cause for increased holiday period death rates is the lack of access to care, as hospitals are often understaffed during holiday seasons, or people may delay seeking treatment in order to spend the holiday at home with family and friends as a first priority. This reason, however, does not account for birthday deaths.
Psychological causes
An evolutionary psychology theory known as terror management theory offers an additional explanation for the Birthday Effect. According to this theory, birthdays remind an individual of their mortality, offering them a chance to reflect on their lives and where they find themselves. This, in turn, can cause an individual to experience increased stress, leading to accelerated death. A similar phenomenon can also be seen in those suffering from suicidal ideation, whereby they may wait until a birthday or significant life event in order to assess whether or not their circumstances will improve before attempting suicide.
An alternative explanation contradicts these theories, however, suggesting that a birthday or holiday offers a terminally ill person a fixed date to focus on, allowing them to hold on until the day itself. Once the day has passed, they allow themselves to let go. This theory can explain both the Passover Effect and the increased terminal illness-related deaths around Christmas.
Can the Birthday Effect be prevented?
Since there is no known reason for the spike in deaths around personal or cultural holidays, there is also no known way to combat it. Medical experts have offered advice on how to stay healthy during the holidays.
A directive issued in Israel by United Hatzalah ahead of the Passover holiday stressed the importance of following safety guidelines in order to reduce the risk of emergency. Included in the list was the importance of bringing medication when traveling, remaining hydrated when spending time hiking outdoors and, in the event that a medical emergency does occur, no time should be wasted in calling the relevant services.