Your birthday may predict your chances of getting certain diseases, according to a new study.
In the study, researchers found that people's birth months were linked with the risk of getting one or more of 55 different diseases. Overall, people in the study who were born in May were least likely to get a birth-month-related disease, whereas people born in October were most likely to get one.
"This data could help scientists uncover new disease risk factors," Nicholas Tatonetti, the senior author of the study and an assistant professor of biomedical informatics at Columbia University, said in a statement.
Previous research had shown that people born in winter — when the days are shorter and people may not get enough sun to produce adequate vitamin D — were more likely to have a vitamin D deficiency, and also may be at increased risk for cardiovascular disease. The researchers of the new study wondered whether people's risk of other conditions also depended on the month of their birth.
They looked at 1.7 million medical records from patients at New York-Presbyterian/Columbia University Medical Center in New York City who were born between 1900 and 2000, and treated between 1985 and 2013. Most people in the study were between ages 20 and 60.
Ten cardiovascular diseases were tied to people's birth month, with people born during the winter months generally having the highest risk, the researchers said. For example, both cardiomyopathy (heart muscle disease) and hypertension (high blood pressure) were highest among those who were January babies, and lowest among people born in September and October.
It's not clear exactly why heart disease risk may be higher in people born during the winter, the researchers said. But it could be that there are more infections in pregnant women during winter months, and that these infections contribute to increased cardiovascular disease among children born at that time of the year.
The study also found that the risk of attention deficit hyperactivity disorder (ADHD) was higher in people born during the later months of the year, with the risk peaking for those born in November. This may be because children born toward the end of the year are more immature compared with their classmates in school, so they may be more likely to be diagnosed with ADHD, the researchers said. [How Your Birth Month Affects Your Risk of Disease (Infographic)]
Although the study population was diverse, the researchers did not look at whether variations in ethnicities or socioeconomic factors could have affected the results, the researchers noted.
Mary Boland, a researcher at Columbia University and lead author of the study, said the researchers would like to expand the study to include data on people living in other locations. She said that different climates and environments could alter the relationship between disease and birth month. However, she expects many of the correlations will stay the same.
“I think the general public will be surprised at this type of result,” Boland told Live Science in an email. The study suggests that the prenatal environment may be important for health later in life, however, people "should not be overly concerned," she said.
Indeed, "The risk related to birth months is relatively minor when compared to more influential variables like diet and exercise," Tatonetti noted.
The study was published in the Journal of American Medical Informatics Association in June.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.