Restless Leg Syndrome and Hormonal Changes in Pregnancy Linked

The higher estradiol levels that are seen during pregnancy are more prominent in pregnant women who have restless legs syndrome (RLS) than in those without, a recent study shows.

Authors of the study, published Feb. 1 2009 in the journal Sleep, say the data suggests that estrogens play a significant role in RLS during pregnancy. This also supports earlier reports of high RLS incidence in the last trimester of pregnancy (when estradiol is at its highest elevation).

In the last trimester, pregnancy levels of the estrogenic steroid hormone known as estradiol were 34,211 pg/mL in women with RLS and 25,475 pg/mL in healthy controls. At three months postpartum, estradiol levels had dropped to 30.73 pg/mL in the RLS group and 94.92 pg/mL in controls. Other hormone levels did not differ significantly between the study groups.

“Our findings strongly support the concept that neuroactive hormones play a relevant pathophysiological role in RLS,” said principal investigator Thomas Pollmacher. “This information will increase the understanding of RLS in pregnancy and will assist in the development of specific therapeutic approaches.”

Sleep Related Disorder

The American Academy of Sleep Medicine classifies Restless Leg Syndrome as a sleep-related movement disorder involving an almost irresistible urge to move the legs at night. The urge has a tendency to go together with unusual feelings or sensations, called “paresthesias,” that occur deep in the legs. These sensations are frequently described as a burning, tingling, prickling or jittery feeling. Needless to say, RLS can greatly disturb a person’s capability to go to sleep or return to sleep after an awakening.

Restless Legs Syndrome occurs 1.5 to two times more often in women than in men, the AASM reports. Eighty to ninety percent of people with RLS also experience periodic limb movements (PLMs) during sleep. PLMs are involuntary jerking or twitching movements of the feet or legs.

According to the study’s authors, RLS symptoms often take place for the first time during pregnancy, with symptoms typically worsening during pregnancy and improving or even disappearing altogether following delivery. The risk of developing RLS also increases slowly but surely with the number of pregnancies.

Periodic Leg Movements

Another finding of the study was that women with RLS had more PLMs than control subjects both before and after delivery. PLMs decreased significantly after delivery in women with RLS and stayed low in women without RLS.

There were only small differences between the two study groups in reported sleep quality and objective sleep measures. A possible explanation suggested by the authors is that only RLS patients who did not need pharmacological treatment were selected for the study; RLS symptoms of participants were in the mild to moderate range.

The study involved nine healthy pregnant women (mean age 32.9 years) who were placed in a control group and 10 pregnant women (mean age 31.6 years) who fulfilled diagnostic criteria for RLS. Eight women from the RLS group reported symptoms previous to the present pregnancy, and all members of the RLS group described worsening of symptoms during pregnancy. The mean age of onset for RLS symptoms was 22.6 years.

Sleep data and leg movements were recorded during overnight polysomnography around the 36th week of gestation and again at 12 weeks postpartum. Blood samples were taken each morning after the polysomnography and before breakfast. Accompanying questionnaires on sleep and RLS symptoms also were collected.

Image by Bill McConkey, Wellcome Images.