MONTREAL – Meningiomas in postmenopausal women are associated with an increased rate of uterine fibroids, low levels of physical activity, and greater height and body mass index, according to an analysis of the Iowa Women’s Health Study.
The link with uterine fibroids is a novel finding, "probably due to shared risk factors," commented Dr. Derek R. Johnson of the Mayo Clinic, Rochester, Minn. "I’m certainly not suggesting it’s causal," he said at the annual meeting of the Society for Neuro-Oncology.
The Iowa Women’s Health study is a prospective cohort of women followed since 1986. Dr. Johnson’s analysis included 27,791 of these women who had completed a follow-up self-report survey in 1993, had no history of cancer, and were enrolled in Medicare.
The mean age of the women was 70 years (in 1993), and their mean body mass index (BMI) at the time of first enrollment was 27 kg/m2.
The analysis found 125 incident meningiomas reported over 291,021 person-years of follow-up, for an overall incidence of 43/100,000 person-years.
BMI was the strongest of the self-reported risk factors for meningioma, with a relative risk (RR) of 2.14 for BMIs greater than 30 compared with BMIs in the normal range of 19.5-24.5 kg/m2. BMI at age 50 and age 40 was positively associated with the risk of meningioma, but BMI at younger ages was not.
Height was the second strongest risk factor for meningioma, with a relative risk of 2.04 for height above 66 inches compared with height of 62 inches or shorter.
Physical activity was protective against meningioma. Compared with a low rate of physical activity, medium and high levels were associated with decreased risk (RR, 0.57 and 0.61).
A history of uterine fibroids carried a relative risk of 1.78, but no other reproductive factors seemed to be correlated. "Fibrocystic breast disease, endometriosis, and some other reproductive covariates have not shown any association, so, with uterine fibroids being so strongly associated, I think it’s not simply a coincidence," Dr. Johnson said.
The associations were significant after adjustment for "current" BMI (1993).
The data raise the hypothesis that a metabolic environment associated with greater growth in adolescence, and greater weight later in life, may play a role in the etiology of meningiomas, he said.
"Potentially the key unifying factor in the things we found in meningioma risk is the influence of circulating sex hormones and insulin resistance," Dr. Johnson said.
Meningiomas occur at twice the rate in women as in men, and the incidence is increasing, he added.
When asked for his opinion on the findings, Dr. Fred Barker of the department of neurosurgery at Massachusetts General Hospital, Boston, said the association with uterine fibroids was intriguing. "It is biologically plausible that the same mechanism of exposure to hormones could explain the association, but it may also be some genetic predisposition, or it may be that women who seek out imaging have both of these things found with relatively minor symptoms."
Many meningiomas in elderly people are small and asymptomatic and are discovered only incidentally or on autopsy, he said in an interview. "As with fibroids, it could just be that certain patient behaviors lead to imaging being done."
Dr. Johnson said he had no relevant financial disclosures.