Women who are fertile for more than 39 years and have natural menopause are at a lower risk of contracting Parkinson's disease, says a new study.
The study, which will be presented at the American Academy of Neurology's 61st Annual Meeting in Seattle, April 25 to May 2, 2009, provides evidence that longer exposure to the body's own hormones may protect women from the disease.
According to the study's results, women who have more years of fertile lifespan (number of years from first menstruation to menopause) had a lower risk of developing the disease than women with fewer years of fertile lifespan. The fertile lifespan is a marker for the body's own sex hormone levels.
In addition, women with four or more pregnancies were at greater risk of developing the disease than women with fewer pregnancies. Separately, the risk of Parkinson's disease was increased in women who had hysterectomies and had also previously taken hormone replacement therapy compared to those who never took hormone therapy, but it was not increased in women who took the hormones but had not had hysterectomies.
"This study does not support a role for treatment with hormone therapy in Parkinson's, but there are still many unanswered questions," said study author Rachel Saunders-Pullman, MD, MPH, MS, of Albert Einstein College of Medicine in Bronx, NY, and Beth Israel Medical Center in New York, NY, and a member of the American Academy of Neurology.
For the study, researchers analyzed the records of the Women's Health Initiative Observational Study to determine who developed Parkinson's disease. The study involved about 74,000 women who underwent natural menopause and about 7,800 women who underwent surgical menopause.