'3 cups of coffee a day may increase migraine risk'

Drinking three or more cups of coffee daily may be associated with a higher risk of migraine, according to a study published Thursday.

Afflicting more than one billion adults worldwide, migraine is the third most prevalent illness in the world, said researchers at Beth Israel Deaconess Medical Center (BIDMC) in the US.

In addition to severe headache, symptoms of migraine can include nausea, changes in mood, sensitivity to light and sound, as well as visual and auditory hallucinations.

The study, published in the American Journal of Medicine, evaluated the role of caffeinated beverages as a potential trigger of migraine.

Led by Elizabeth Mostofsky, from the Harvard T H Chan School of Public Health (HSPH) in the US, the researchers found that, among patients who experience episodic migraine, one to two servings of caffeinated beverages were not associated with headaches on that day.

However, three or more servings of caffeinated beverages may be associated with higher odds of migraine headache occurrence on that day or the following day.

"While some potential triggers -- such as lack of sleep -- may only increase migraine risk, the role of caffeine is particularly complex, because it may trigger an attack but also helps control symptoms," said Mostofsky.

"Caffeine's impact depends both on dose and on frequency, but because there have been few prospective studies on the immediate risk of migraine headaches following caffeinated beverage intake, there is limited evidence to formulate dietary recommendations for people with migraines," he said.

In the study, 98 adults with frequent episodic migraine completed electronic diaries every morning and every evening for at least six weeks.

Every day, participants reported the total servings of caffeinated coffee, tea, soda and energy drinks they consumed, as well as filled out twice daily headache reports detailing the onset, duration, intensity, and medications used for migraines since the previous diary entry.

Researchers used a self-matched analysis, comparing an individual participant's incidence of migraines on days with caffeinated beverage intake to thier incidence of migraines on days with no caffeinated beverage intake.

This self-matching eliminated the potential for factors such as sex, age, and other individual demographic, behavioural and environmental factors to confound the data.

The researchers further matched headache incidence by day of the week, eliminating weekend versus week day habits that may also impact migraine occurrence.

Self-matching also allowed for the variations in caffeine dose across different types of beverages and preparations.

"One serving of caffeine is typically defined as eight ounces or one cup of caffeinated coffee, six ounces of tea, a 12-ounce can of soda and a 2-ounce can of an energy drink," said Mostofsky.

"Those servings contain anywhere from 25 to 150 milligrammes of caffeine, so we cannot quantify the amount of caffeine that is associated with heightened risk of migraine.

The researchers saw no association between one to two servings of caffeinated beverages and the odds of headaches on the same day, but they did see higher odds of same-day headaches on days with three or more servings of caffeinated beverages.

However, among people who rarely consumed caffeinated beverages, even one to two servings increased the odds of having a headache that day, researchers said.

"Despite the high prevalence of migraine and often debilitating symptoms, effective migraine prevention remains elusive for many patients," said Suzanne M Bertisch from BIDMC.