AS A DIEHARD astrology sceptic鈥攁 common trait in Sagittarians鈥擨
never thought my birth date revealed much about anything, apart from pinpointing
that fateful month all those years ago when my parents were feeling frisky. But
now I have to consider that it may be responsible for my hopelessness at
cricket, my rejection from medical school and the fact that I鈥檓 not tall enough
to reach the top shelf in the supermarket. I鈥檓 also likely to live to a ripe old
age, and although I鈥檒l probably grow fat if I do, at least I鈥檓 unlikely to get
depressed about it.
Astrology has had an avid following since the year dot. It has played an
important role in world affairs, even guiding the decisions of world leaders
from Emperor Tiberius to US President Ronald Reagan. But for millennia, sceptics
have relentlessly derided astrology as a pseudoscience that preys on our
gullibility. While fans of astrology turn to the stars, scientists have been
turning to statistics. And most scientific work casts astrology in a pretty dim
light.
But a growing body of research shows that there might indeed be some curious
seasonal trends in our physical and mental characteristics. A steady trickle of
papers published in learned journals have claimed that the prevalence of all
sorts of skills and traits varies with date of birth.
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For a start, there are some intriguing trends in sporting prowess. A study by
psychologist Ad Dudink of the University of Amsterdam found that English
professional soccer players in the 1991-92 season were almost twice as likely to
have been born between September and November as during the summer months. And
it鈥檚 not just footballers who can celebrate their birthdays en masse; cricketers
are also fruits of the season. Stephen Edwards from the University of Wales,
Swansea found that fast bowlers were more likely to have been born in the early
part of the year鈥攁lthough for some reason, he found no such trend among
spin bowlers.
These strange correlations aren鈥檛 confined to sporting spheres. Another study
from Swansea, found that children born in Britain during the summer were 50 per
cent more likely to need special help at school. Two more studies, one from
Portugal and the other from Italy, found that more medical students have
birthdays between April and June than could be explained by chance alone.
A deeper trawl through the literature nets evidence for seasonal correlations
in average height, weight and longevity. In 1998, Gerhard Weber of the
University of Vienna completed a study examining the average heights of over
half a million 18-year-olds conscripted into the Austrian army over a 10-year
period. He found a striking relationship between average height and month of
birth, with men born between March and May being on average 6 millimetres taller
then those born between September and November.
Curiously, people born in winter tend to get fatter in later life, according
to a study soon to be published by David Phillips of the Medical Research
Council Environmental Epidemiology Unit (EEU) in Southampton. Winter babies also
tend to live longer, according to Gabrielle Doblhammer of the Max Planck
Institute for Demographic Research in Rostock, Germany.
Perhaps the most unusual seasonal effect is found amongst scientists who
support revolutionary theories. It seems that academics who were quick to
support controversial theories such as relativity and evolution tended to be
born between October and April. 鈥淚 wasn鈥檛 actually looking at birthdays, I was
trying to understand why scientific revolutions like relativity come about, but
I suppose I was unconsciously clocking up patterns in my head,鈥� says Michael
Holmes, a psychologist from Queen Margaret鈥檚 College in Edinburgh, who published
his study in Nature (vol 373, p 468). 鈥淚 didn鈥檛 take it too seriously,
but then I looked at evolution and found the same summer-winter pattern,鈥� he
says.
Festive frolicks
Why there should be any patterns at all is anyone鈥檚 guess. One factor that
confuses the issue is that birth and death rates fluctuate with the seasons.
There is a peak in births in September鈥攗sually blamed on people getting
carried away at Christmas and New Year festivities鈥攁nd random rises in
birth rates after prolonged power cuts or strikes by electricity workers. Harsh
weather increases the number of deaths, and frail people often cling to life
like limpets as they approach their birthday, only to give up the ghost shortly
after. All these effects can skew the pattern.
But these fluctuations can鈥檛 account for all the correlations that scientists
find. Of course, there are more mundane explanations for variations in sporting
and academic ability, such as the timing of birth in relation to the academic
year and the start of the sporting season. But it鈥檚 also possible that there is
a biological basis to these trends. 鈥淚t could have something to do with external
influences like sunlight and temperature,鈥� says Weber.
Ideas like this are moving the study of seasonal effects out of the realms of
astrology into the arena of epidemiology. A growing body of literature that has
languished largely unnoticed for at least 70 years shows that the season in
which you are born could influence your chances of developing diabetes,
arthritis, heart disease, schizophrenia, depression and allergies such as hay
fever and asthma.
鈥淲hen I first published my results in the 1970s, people said this can鈥檛
possibly be true,鈥� says Fuller Torrey a research psychiatrist at the Uniform
Services University of the Health Sciences in Bethesda, Maryland. He has
undertaken a review of studies relating to schizophrenia and manic depression
from 1929 to the present day, and found that more people with these disorders
were born between December and April than would be expected by chance. He points
out that there are more than 250 studies now backing this trend. 鈥淲hatever
hypothesis you use to explain schizophrenia needs to account for this,鈥� he
says.
鈥淭he fact that seasonal effects exist shows that environmental factors might
exist,鈥� says Patricia McKinney, an epidemiologist at Leeds University, who has
researched childhood diabetes. 鈥淥ne interpretation is that there are more
infections occurring during pregnancy and early life that have some role in the
development of childhood diseases.鈥� The role of viruses could explain a lot here
too, as their activity and prevalence varies with the time of year鈥攁s
anybody who鈥檚 caught a dose of the flu in winter will testify.
David Barker of the EEU in Southampton has done some of the pioneering work
looking at how what happens to a fetus in the womb can influence later life (see
快猫短视频, 17 July, p 27). 鈥淚t鈥檚 a nonsense to say that seasonal
correlations are artefacts. Every human is massively programmed by in utero
effects,鈥� he says. 鈥淪cience is stuck in a bit of a rut saying that what happens
at conception is very important as is what happens when you are forty, but there
is this big gap in between.鈥�
Of course, as with all statistical correlations, there is always the
possibility of the odd spurious result. Rory Collins of the Clinical Trial
Service Unit at Oxford University demonstrated this beautifully in his study on
the effects of daily doses of aspirin on people who had suffered a heart attack
or a stroke. He found that aspirin significantly decreased the risk of a second
attack. But a less highly publicised facet of the work was that when Collins
analysed the data in monthly blocks, split according to star sign, it looked as
though giving aspirins to Geminis or Librans actually increased the risk of a
second attack. 鈥淚 still think our study shows it鈥檚 good to give heart attack
patients aspirin regardless of their star sign,鈥� says Collins.
These spurious findings show just how easily strange correlations arise
purely by chance. If you divide the data from a study into enough different
subgroups, eventually one particular group will contain people who, possibly for
entirely different reasons, might show trends which contradict those emerging
from the study as a whole. 鈥淥urs was just statistical sleight of hand to show
how we could manipulate the data and get spurious results,鈥� says Collins.
So, where does all this leave astrology? Is there more to it than the
sceptics would have us believe, or should it just be slung in the mumbo-jumbo
dustbin of scientific history? Well, I鈥檓 afraid I鈥檒l have to leave that one up
to you. My horoscope says that this week is a bad time for me to make important
decisions.