Parkinson’s in women: the onset of the disease linked to hormonal life

A degenerative disease, Parkinson’s disease affects approximately 200,000 people in France, including 25,000 new cases per year, while being 1.5 times more common in men than in women. As such, many researches are carried out on male populations to know the risk factors, but very little on female populations. But a new study conducted by Inserm’s Center for Research in Epidemiology and Population Health focused on women, their lives, their exposure to hormones and the links with the disease.

+ 80% risk for a woman who has undergone treatment to stimulate ovulation

The French study compared the characteristics relating to the reproductive history of nearly 1,200 women with Parkinson’s disease to those of other women in the E3N cohort, a strong cohort of 100,000 women followed over 24 years. Their results show above all 4 risk factors which probably link hormones and the onset of Parkinson’s disease.

Their results show that the age of the first menstruation, the number of pregnancies, the type of menopause as well as a molecule administered to improve fertility in particular, can have a role in the onset of the disease.

• Women whose first menstruation occurred before or after 12-13 years showed an increased risk of respectively +21% and +18%;
• If the fact of having or not having children was not associated with the risk of developing the disease, among women who had children, this risk increased with the number of births (+ 22% for the second child, + 30% at from the third);
• An artificial menopause would be associated with a 28% increased risk compared to a natural menopause, and more pronounced when it occurs before the age of 45 (+ 39% risk compared to a menopause occurring after 45 years) or when ‘it is the consequence of removal of both ovaries – with or without removal of the uterus (+ 31% compared to a natural menopause);
• Finally, if treatments to improve fertility were not associated with an overall increased risk of Parkinson’s disease, taken individually, clomiphene – a treatment stimulating ovulation – would increase the risk by 80% compared to women who have never taken fertility treatment.

The protective role of estrogen highlighted?

Another discovery or confirmation, identified during the long-term study: the protective role that estrogen seems to have. Thus, exposure to insufficient levels of female hormones (estrogens) could also be involved in the onset of the disease.

Marianne Canonico, researcher at Inserm, explains: “Artificial and/or early menopause causes ovarian failure and consequently a sudden and anticipated drop in estrogen levels, normally still high before the age of 45, as for clomiphene, it has an anti-estrogen role” .

This hypothesis is supported by the observation of a protective effect of hormonal treatments used at menopause, which seem to attenuate the risk linked to early or artificial menopause for Parkinson’s disease.

Identify populations at risk, to better support them

Contacted by Doctissimo, Marianne Canonico, explains the importance of this study.

“This is not the first time that these links between hormones and Parkinson’s have been studied, but the previous studies were of smaller sizes, and did not have the necessary time perspective that we can have on this E3N cohort carried out over 30 years. This decline is significant in Parkinson’s disease since there is a very long latency phase between exposure, which may have an effect, and the onset of the disease much later. Our study allows this highlighting”.

The researcher also tells us about the importance of carrying out such work on an exclusively female population:

Finally, by focusing on the risk factors of a targeted population, it is possible to better understand the physiopathology of Parkinson’s and to have therapeutic leads.