WASHINGTON (Reuters) - Acupuncture works better than drugs like aspirin to reduce the severity and frequency of chronic headaches, U.S. researchers reported on Monday.

A review of studies involving nearly 4,000 patients with migraine, tension headache and other forms of chronic headache showed that that 62 percent of the acupuncture patients reported headache relief compared to 45 percent of people taking medications, the team at Duke University found.

"Acupuncture is becoming a favorable option for a variety of purposes, ranging from enhancing fertility to decreasing post-operative pain, because people experience significantly fewer side effects and it can be less expensive than other options," Dr. Tong Joo Gan, who led the study, said in a statement.

"This analysis reinforces that acupuncture also is a successful source of relief from chronic headaches."

Writing in Anesthesia and Analgesia, they said 53 percent of patients given true acupuncture were helped, compared to 45 percent receiving sham therapy involving needles inserted in non-medical positions.

"One of the barriers to treatment with acupuncture is getting people to understand that while needles are used, it is not a painful experience," Gan said. "It is a method for releasing your body's own natural painkillers."

They found it took on average five to six visits for patients to report headache relief.

Other studies have shown that acupuncture helped alleviate pain in patients who had surgery for head and neck cancer, can relieve hot flashes and other menopausal symptoms and can reduce chemotherapy-induced nausea.

(Reporting by Maggie Fox; Editing by Julie Steenhuysen)