Women with sleep problems have triple the risk of developing fibromyalgia -- a condition marked by chronic, widespread pain and fatigue -- according to a new study published in the journal Arthritis & Rheumatism.

The study involved more than 12,000 women age 20 and older with no chronic pain when the study began in the mid-1980s, although one-third reported some difficulty sleeping. Ten years later, about 3 percent reported developing fibromyalgia. Those who initially reported sleep problems were three and a half times more likely to have developed fibromyalgia, especially among women 45 or older.

Although previous research has shown that poor sleep is linked to fibromyalgia, this is the largest study involving women who were initially pain-free and then developed the fibromyalgia.

Despite the researchers relying only on the women's own assessment of their condition, and failing to control for anxiety levels, which has been linked to both sleep problems and fibromyalgia, the results support the importance of sleep in fibromyalgia, said Lesley Arnold, Ph.D., a professor of psychiatry and behavioral neuroscience at the University of Cincinnati College of Medicine.

"We don't always understand what the biological mechanisms are underlying that association between sleep and pain, but clearly there's an important connection," Dr. Arnold said.

Fibromyalgia mostly affects women - some 90 percent of patients with the condition are women - and an estimated 5 million adults in the U.S. have the disorder. Most are diagnosed during middle age.