“Amongst the most readily cited but poorly studied triggers of headaches are these weather related variables,” said Gregory A. Wellenius, one of the co-authors of the study. “Although there have been a number of earlier studies linking headaches with weather conditions, the large, better studies of weather effects have really had mixed results.”
The classic methods of studying headaches involve comparing the number of people coming into emergency rooms for headache-related causes in the winter as opposed to the summer, or to ask patients to keep diaries. But these methods don’t necessarily illustrate the triggers of headaches.
“A trigger is: why did something happen to you today?” said Kenneth J. Mukamal, the first author of the study. “What was the acute thing that brought this event right now?”
The researchers took an individualized approach in order to ascertain what specifically was causing headaches. They looked at records of 7,054 headache patients over a 7-year period who came in to the emergency room of BIDMC and compared weather and pollution levels before and after each patient experienced severe headaches.
This method was first developed at Harvard, according to Wellenius, and its advantage is its independence from the type of population it is studying.
“If I were to ask how many people came to Harvard Health Services every month of the year it would be obvious that headaches are much worse in the winter, because that’s when the students are around. But in the summer, miraculously they would all go away,” Mukamal said. “In our case, we are not reliant on the population. We are asking each individual what happened to trigger his or her headache.”
While this study establishes a correlative relationship rather than a causal one, it could influence the way patients and clinicians alike think about headaches.
“People could try to be careful on warmer days,” Mukamal said. “It [also] encourages us to keep an open mind about what kind of triggers we should be looking for.”
The study also raises the broader issue of the relationship between the ongoing environmental changes and public health.
“It’s important to recognize that this starts to build a case for the public health impact by environmental changes over time, and how this may influence lots of different diseases including severe headaches,” Wellenius said.