For the study, "scientists examined seven years of records of more than 7,000 people with a primary diagnosis of headache seen in a hospital" emergency department (ED) in Boston, Nicholas Bakalar writes in the New York Times (3/10, D6) Vital Signs column. They also analyzed "data on temperature, humidity, barometric pressure and air pollution during the three days before each visit." The study showed that "for each rise of nine degrees Fahrenheit...the risk of a headache requiring [ED] treatment rose 7.5 percent." Notably, "there was no connection between headache frequency and air pollution levels in the days before emergency visits, except for a slightly higher risk for nonmigraine headaches on days of high nitrogen dioxide readings."

BBC News (3/10) adds that the researchers also found that "lower barometric air pressure, which typically brings cloudy or stormy skies, within two or three days leading up to a person's hospital visit also increased headache risk." Data indicated that "overall, 2,250 were diagnosed with migraine and 4,803 with 'tension' or 'unspecified' headaches." Commenting on the findings, researcher Dr. Kenneth Mukamal, of the Beth Israel Deaconess Medical Center, stated that "the environment around us does affect our health and, in terms of headaches, may be impacting many, many people on a daily basis."

"High temperatures alone, such as those in the summer, were not as much of a trigger. The most influential factor was whether a particular day was hotter than expected," HealthDay (3/9, Dotinga) pointed out. While the reason behind "the effect of temperature" remained unclear, Dr. Richard Lipton, director of the Montefiore Headache Center at Montefiore Medical Center in New York City, speculated that "barometric pressure could affect the layer of fluid that protects the brain inside the skull." MedPage Today (3/9, Smith) also covered the story.