Hot weather may trigger migraine

While many of us are looking forward to some hotter weather in the coming months, a new study appears to confirm that higher temperatures may increase the severity of migraine headaches.

Migraine is Ireland's most common neurological condition, affecting over 400,000 people. It is characterised by a severe, one-sided headache that can last up to three days. It can be accompanied by symptoms such as nausea, vomiting and sensitivity to light and/or noise.

According to US researchers, a large number of headache sufferers, particularly those affected by migraine, attribute their pain, in part, to the weather. However there has been little scientific evidence to back this up. Knowing that migraines can be set off by triggers, including certain foods, alcohol and stress, the team decided to study whether environmental factors were also acting as headache triggers.

“Air temperature, humidity and barometric pressure are among the most frequent reasons that people give for their headache pain. But none of these reasons have been consistently verified. We wanted to find out if we could verify this ‘clinical folklore.’ We also wanted to determine whether air pollutants trigger headaches, much as they have been found to trigger strokes,” explained study author, Dr Kenneth Mukamal of the Beth Israel Deaconess Medical Center in Boston.

The researchers looked at over 7,000 patients who attended A&E units between May 2000 and December 2007, whose primary diagnosis was headache. Of these, 2,250 were diagnosed with migraine.

Using weather and pollution monitors, they compared measurements of a number of environmental factors, including air temperature, humidity, barometric pressure and fine particulate matter (air pollution), in the three days before the patient attended hospital and then again at corresponding dates. This was carried out to determine whether these factors triggered the severe headaches.

“In other words, our study design was able to directly compare weather and air pollution conditions right before an emergency visit with those same factors measured earlier and later the same month,” Dr Mukamal said.

The study found that of all the environmental factors considered, higher air temperature in the 24 hours prior to the patient’s A&E visit was most closely linked with headache symptoms. In fact, for every five degree Celsius increase, there was a 7.5% higher risk of a severe headache.

The study also noted a link between barometric pressure and migraine, although this was to a lesser degree. It found that lower pressure 48 to 72 hours before a patient’s A&E visit also appeared to trigger a headache.

The researchers found no evidence that air pollutants influenced the onset of headache, but could not rule out a smaller effect similar to that previously seen for stroke.

“Certainly our results are consistent with the idea that severe headaches can be triggered by external factors. These findings help tell us that the environment around us does affect our health and, in terms of headaches, may be impacting many, many people on a daily basis,” Dr Mukamal said.

He recommended that headache patients sit down with their doctors to identify the triggers that lead to their headache symptoms, adding that even though the weather cannot be altered, doctors might be able to prescribe medication to help avert the onset of weather-related headaches.

He added that on a population basis, ‘we need to be concerned about incremental temperature rises and should advocate for responsible environmental management’.

Details of these findings are published in the journal, Neurology.

[Posted: Tue 10/03/2009]