Study Finds How Your Birth Month Affects Your Health

The relationship between birth month and disease incidence in 1.7 million patients. Good news if you were born in May. Not so much if you were an October baby. (Graphic: Columbia University Medical Center)

Mary Boland, a PhD student at Columbia University Medical Center, was investigating old studies relating the time of year a person is born to the odds of developing asthma, when she had the idea for her team’s new study published this week in the Journal of the American Medical Informatics Association: Does your birth month affect your health outcomes later in life?

“It turns out that if a newborn is exposed to high levels of dust mites in their first few months of life that they have higher incidence of a certain type of asthma later,” says Nicholas Tatonetti, PhD, an assistant professor of biomedical informatics at Columbia University Medical Center and Columbia’s Data Science Institute. “This kind of study has been done quite a bit in a one-off fashion, studying this disease or that disease. … We were curious if we could recapitulate some of those early findings.”

And so they did.

With access to data on 1.7 million patients treated at NewYork-Presbyterian Hospital/Columbia University Medical Center between 1985 and 2013, the researchers used an algorithm to look at relationships between birth month and disease risk. The goal was to see if there were any spikes in specific diseases at certain times of year.

Overall, May babies seem to have the lowest disease risk and October babies have the highest.

In fact, the scientists found 55 diseases that correlated with the season of a person’s birth, and also uncovered 16 entirely new correlations — including nine types of heart disease.

“The most striking was a trend we found that those born in late winter or early spring were more likely to have heart disease,” Tatonetti tells Yahoo Health. “And we didn’t find just one type of heart disease associated with birth month, but we actually found several.”

The average life span for each birth month, which shows that those born in the first half of the year tend to have shorter lives. (Graphic: Columbia University Medical Center)

People born in March have the highest risk of atrial fibrillation, congestive heart failure and mitral valve disorder, and the scientists suggest that 1 in 40 cases is related to a seasonal variable. The scientists suggest this may have something to do with fluctuating levels of vitamin D. Since heart disease is the leading cause of death in the United States, this could help doctors hone in on early prevention strategies.

The incidence of disease per birth month, which shows higher incidences in those with earlier birthdays. (Graphic: Columbia University Medical Center)

Month-related disease risks may often be determined by changing environmental and circumstantial factors. For example, the researchers found that asthma risk for New York patients peaked with July and October births. A previous study conducted in Denmark found that risk was heightened for people born in the months of May and August — when the country’s sunlight levels are most similar to New York’s. Sunlight is a factor in asthma exacerbated by dust mites.

The number of disease associations per birth month. (Graphic: Columbia University Medical Center)

Perhaps ADHD diagnoses spike with births later in the year (late November), because of the relative immaturity of these children compared with their peers in school. The age cutoff for schoolchildren in New York City is Dec. 31, meaning higher demands are placed on them earlier, with less time for development.

The researchers hope this sort of data may help uncover new risk factors for some diseases. However, Tatonetti says that, while significant for future study, there’s no need to panic about your month-related disease risks.

“The risk we found that can be attributed to birth month is on par with what you would find from genetic analyses,” he explains. “Lifestyle, diet, and exercise are still stronger factors when considering your health.”

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