Scientists have long noticed a strange correlation between when we're born and how likely it is that we'll experience certain health problems, including allergies.
Thanks to an international team of researchers, we now can at least partly explain how this happens: The season you were born in can leave certain "markers" on your DNA that may influence your health, said Dr. John Holloway, professor of allergy and respiratory genetics at the University of Southampton in England and a co-author of the new study.
"If we can go on to identify what it is about season of birth that causes these changes, this could potentially be modifiable, allowing the development of preventative strategies for allergies," he told The Huffington Post.
For the study, which was published in the journal Allergy on Tuesday, researchers scanned DNA samples from 367 18-year-olds who were born on the Isle of Wight in England. They analyzed specific markers, called DNA methylation, in the samples, and examined whether different markers could be associated with what time of year a person was born and whether they suffer from any allergic diseases, including asthma and eczema.
The researchers then measured how susceptible each person was to developing such allergies and noted which participants reported suffering from hay fever, asthma or eczema when they were 1, 4, 10, and 18 years old, Live Science reported.
It turns out that we carry certain DNA markers into adulthood -- and that some are both associated with the season we're born in and whether it's likely we'll develop certain allergies.
For example, the researchers linked being born in the fall with an increased risk of eczema. Children born in autumn or winter may have a higher chance of developing asthma, The Telegraph reported.
[T]he epigenetic marks discovered in this study could also potentially be the mechanism for other seasonally influenced diseases and traits too, not just allergy. Dr. Gabrielle Lockett, researcher at the University of Southampton
Similar findings emerged when the researchers looked at markers found in a group of 8-year-olds. However, the researchers didn't see the markers when they tested their findings in a group of newborn babies -- which suggests that DNA methylation changes might be a result of a person's environment and not occur while in the womb.
"It might sound like a horoscope by the seasons, but now we have scientific evidence for how that horoscope could work," Dr. Gabrielle Lockett, a postdoctoral researcher at the University of Southampton and first author of the study, said in a statement. "Because season of birth influences so many things, the epigenetic marks discovered in this study could also potentially be the mechanism for other seasonally influenced diseases and traits too, not just allergy."
Last year, for instance, data scientists at Columbia University Medical Center in New York discovered an odd correlation between the month a person was born and their risk of developing not only allergies but also health problems including heart disease, viral infections and attention deficit hyperactivity disorder. Previous studies have also linked season of birth with the risk of some food allergies.
More research is needed to explore these associations, as Holloway said it's unclear why they exist.
"It could be, for example, sunlight levels affecting maternal vitamin D levels either when the baby is in utero or in breastmilk after birth. It could be a postnatal effect determined by season of birth -- such as, does the child encounter it’s first winter cold season shortly after birth or after nine months when its immune system is more mature," he said. "Is it something to do with mother’s diet as the nutrient content of our diets have been shown to vary with the season? ... We don’t know, but this is what we hope to go on to find out."