Caffeine intake may be associated with lower incidence of unexplained ear ringing, according to a recent study.

Researchers from Brigham and Women's Hospital found people with a higher intake of caffeine has a lower incidence of tinnitus, often described as a ringing or buzzing sound in the ear "when there is no outside source of the sounds, in younger and middle-aged women.

"We observed a significant inverse association between caffeine intake and the incidence of tinnitus among these women," Gary Curhan, senior author of the study and a physician-researcher in the Channing Division of Network Medicine at Brigham and Women's Hospital and Professor of Medicine at Harvard Medical School, said in a statement.

Researchers followed more than 65,000 women in the Nurses' Health Study II, tracking self-reported results regarding lifestyle and medical history from these women. The study participants were between the ages of 30 and 44 and without tinnitus in 1991. Information on self-reported tinnitus and date of onset was obtained from questionnaires returned in 2009, with cases defined as women who reported symptoms "a few days/week" or "daily." After 18 years of follow up, researchers identified 5,289 cases of reported incident tinnitus.

They found that when compared with women with caffeine intake less than 150 milligrams/day (approximately one and a half 8-ounce cups of coffee), the incidence of reported tinnitus was 15 percent lower among those women who consumed 450 to 599 mg/day of caffeine. The majority of caffeine consumed among the women was from coffee and the results did not vary by age.

"The reason behind this observed association is unclear," Curhan said. "We know that caffeine stimulates the central nervous system, and previous research has demonstrated that caffeine has a direct effect on the inner ear in both bench science and animal studies."

Researchers note that further evidence is needed to make any recommendations about whether the addition of caffeine would improve tinnitus symptoms.

The findings were recently published in the American Journal of Medicine.