People who received frequent dental X-rays in the past, before dosages were lowered, have an increased risk of developing a meningioma, the most common and potentially debilitating type of non-cancerous brain tumor, a new study led by the Yale School of Public Health has found.

The study is published online in Cancer, a journal of the American Cancer Society.

Meningioma is listed as a rare disease by the National Institutes of Health. The estimated incidence is up to 8 out of 100,000 people, and it occurs more frequently among women than men. Although it is the most frequently diagnosed type of brain tumor, meningioma is listed as a rare disease by the National Institutes of Health. Tumors develop in a membrane that envelops the brain and the central nervous system known as the meninges. They can grow undetected for years and eventually reach the size of a baseball or larger. While they are not cancerous, they can cause debilitating side effects such as headaches, vision problems, and loss of speech and motor control.

The researchers analyzed data from 1,433 patients who were diagnosed with the disease and were residents of Connecticut, Massachusetts, North Carolina, California, and Texas. The investigators also included information from a control group of 1,350 individuals with similar characteristics who did not have the tumor. The mean age was just over 57 years for both groups.

The study found that over a lifetime, individuals who developed meningioma were more than twice as likely as those in the control group to report having received bitewing exams (which use X-ray film held in place by a tab between the teeth) on a yearly or more frequent basis.

The researchers also found a link between meningioma risk and the panorex dental exam (which uses an X-ray outside of the mouth to develop a single image of all of the teeth). The authors write that significant increases in risk were associated with young age at the time of screening, as well as more frequent screening. Individuals younger than 10 years old who received this exam in the past had a nearly five times greater risk of developing meningioma. Among people of all ages, those who received the panorex exam on a yearly or more frequent basis were up to three times more likely to develop a tumor.

While today's patients are exposed to lower X-ray doses than in the past, the American Dental Association stresses the need for dentists to examine the risks and benefits of dental X-rays and has confirmed that there is little evidence to support the use of dental X-rays of all teeth in patients who are not experiencing symptoms.

"The study highlights the need for increasing awareness regarding the optimal use of dental X-rays, which unlike many risk factors, is modifiable," said lead author Elizabeth Claus, a professor at Yale and a neurosurgeon at Brigham and Women's Hospital in Boston.

The American Dental Association's guidelines for healthy persons suggest that children receive one X-ray every one to two years; teenagers every one and a half to three years, and adults every two to three years, Claus said.

Other authors are Joseph Wiemels and Margaret Wrensch of the University of California-San Francisco, Joellen Schildkraut of Duke University, and Melissa Bondy of the Baylor College of Medicine.

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