Approximately 75% of patients who carry 1 copy of the BTBD9 gene on chromosome 6 were shown to have an increased risk of restless leg syndrome (RLS) with periodic leg movements in sleep (PLMS) compared with patients who do not have the variant. 1 Fifty percent of the study patients with RLS were carriers, and being a carrier also was associated with decreased iron levels.

Furthermore, patients with moderate to severe RLS are at significantly increased risk for developing hypertension, according to David Rye, MD, PhD, professor of neurology at Emory University School of Medicine, and colleagues in Iceland. Rye presented the data at the 21st Annual Meeting of the Associated Professional Sleep Societies in Minneapolis on June 12.

Using a triaxial accelerometer, 861 Icelandic patients with RLS were examined for 2 to 5 nights for signs of PLMS. Results showed that risk of hypertension increased with PLMS severity. More than 50% of patients with more than 30 PLMS per hour had hypertension.

Although older age and body mass index predicted hypertension status, these factors were not associated with PLMS. Risk of hypertension also was not associated with the a patient's score on the International Restless Legs Syndrome Study Group rating scale or with the duration of RLS symptoms. Rye's team concluded that the PLMS seen in most patients with RLS are associated with increased release of adrenaline.

The citation for the study is Stefansson H, Rye DB, Hicks A. A genetic risk factor for periodic limb movements in sleep. N Engl J Med. 2007;357:639-647.