A new study from a University of Maryland researcher shows that in years when the state’s trees bloom early, asthma hospitalizations jump.

The study, published this month in the Journal of the American Medical Association, is the first to provide quantitative data to link climate change—which is altering the onset of spring and seasonal timing of plant cycles—with asthma-related medical complications.

“Prior studies have shown that changes in plant phenology, such as the timing of spring onset, timing of particular flower bloom, growing season length, are the most sensitive indicator of the ecological response to climate change,” said Amir Sapkota, a professor of applied environmental health in the School of Public Health and the lead author of the study. 

To understand the link between climate change and asthma hospitalization in Maryland, the researchers merged 29,257 springtime asthma hospitalizations from 2002 to 2012  with satellite data about the start of spring from NASA’s Moderate Resolution Imaging Spectroradiometer. Then categorized the timing of spring onset for each of those years across localities in Maryland as very early, early, normal or late. 

In years with a very early onset of spring, they found a 17% increase in asthma hospitalizations, while the late start of spring was associated with a 7% increase.

The researchers hypothesize that early spring onset lengthens the tree pollen season, which negatively impacts asthmatic individuals. Likewise, late onset of spring likely results in a more intense pollen season because different tree species bloom simultaneously, increasing the risk, Sapkota said.

The findings are meaningful beyond Maryland and affect many millions of Americans—both asthma sufferers and those rendered miserable by springtime allergies. 

According to the Centers for Disease Control and Prevention, 8% of Americans suffer from asthma, and that costs the U.S. economy over $80 billion every year in treatment expenses and loss of productivity, Sapkota said. “Our data show that ongoing climate change will further exacerbate the asthma burden in our backyard.”

The researchers suggest developing early warning systems that will inform health care providers and patients about the timing of spring pollen season as well as peak pollen concentration, and influence asthma management guidelines amid a changing climate.