New research links obesity to an increased risk of severe headaches.

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The study measured the influence of body mass index (BMI) on frequency, severity and the potentially disabling effects of headaches. A person's BMI, in part, determines weight-related health problems based on height and weight.

"The findings suggest that people with obesity were more likely to report frequent, more painful, and more debilitating headaches than other groups we encountered," said Dr. Marcelo E. Bigal, the study's lead author, in a news release.

The research presented this week at a meeting of the American Academy of Neurology.

Researchers identified more than 30,000 people out of almost 144,000 as having at least one severe headache attack in the previous year. They then classified each of those people into four BMI types, including underweight, normal weight, overweight and obese. They also analyzed a fifth group of people classified as morbidly obese.

A majority of the 30,000 people observed were female. The average age was 43.

They found that chronic daily headaches are more prevalent in obese and morbidly obese people than those with normal body weight.

Researchers said 33 percent of the obese people missed more than four days of work in one year due to severe headaches. In comparison, a little more than one-fourth of overweight, normal weight and underweight people missed days at work.

Obese people also reported severe pain more often than the other groups. Those with morbid obesity reported that the pain was usually severe more than 40 percent of the time.

The length of time for headache pain did not differ significantly among the groups. But the underweight group reported headaches accompanied by nausea more frequently than the other groups.

IMR Inc., a division of Caremark, collected the data, and Ortho-McNeil Pharmaceutical Inc., a division of Johnson & Johnson, supported the analysis.