Elevated C-reactive protein is associated with severe periodic leg movements of sleep in patients with restless legs syndrome.

Abstract

Restless legs syndrome (RLS) is a common sleep disorder in which urges to move the legs are felt during rest, are felt at night, and are improved by leg movement. RLS has been implicated in the development of cardiovascular disease. Periodic leg movements (PLMs) may be a mediator of this relationship. We evaluated systemic inflammation and PLMs in RLS patients to further assess cardiovascular risk. 137 RLS patients had PLM measurements taken while unmedicated for RLS. Banked plasma was assayed for high sensitivity C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha). Mean (SD) PLM index was 19.3 (22.0). PLMs were unrelated to TNF-a and IL-6, but were modestly correlated with logCRP (r(129)=0.19, p=0.03). Those patients with at least 45PLMs/h had an odds ratio of 3.56 (95% CI 1.26-10.03, p=0.02, df=1) for having elevated CRP compared to those with fewer than 45PLMs/h. After adjustment for age, race, gender, diabetes, hypertension, hyperlipidemia, inflammatory disorders, CRP-lowering medications, and body mass index, the OR for those with ≥ 45PLMs/h was 8.60 (95% CI 1.23 to 60.17, p=0.03, df=10). PLMs are associated with increased inflammation, such that those RLS patients with at least 45PLMs/h had more than triple the odds of elevated CRP than those with fewer PLMs. Further investigation into PLMs and inflammation is warranted.