Objectives To assess the prevalence of restless leg syndrome (RLS) in patients with ankylosing spondylitis (AS) and to investigate factors potentially associated with RLS.
Methods 130 patients diagnosed with AS (95M, 35F, mean age: 38.4) according to modified New York criteria and age-and-sex matched 91 healthy control subjects (66M, 25F, mean age: 37.6) were included in this study. The diagnosis of RLS was made according to the criteria of the International RLS Study Group. The factors associated with RLS were evaluated. Electrophysiological procedures were performed in a group of patients with RLS.
Results The frequency of RLS was significantly higher in AS patients (30.8%) than in healthy subjects (13.2%) (p=0.002).
When AS patients with RLS was compared with AS patients without RLS, it was seen that peripheral arthritis (60% vs 26.7%, p<0.001), uveitis (25% vs 8.8%, p=0.016), iron deficiency anemia (62.5% vs 24.4%, p<0.001) and smoking (60% vs 30%, p=0.001) were significantly higher in the former group. AS patients with RLS tended to be have a younger mean age than others (p=0.088).
We also evaluated cutaneous silent period in a subgroup AS patients with and without RLS. The mean level of upper extremity (87.6+10.6 vs 76.8+10, p=0.004) and lower extremity latency (123.9+22.6 vs 105.9+18.7, p=0.017) were significantly higher in AS patients with RLS than in AS patients without RLS. The mean duration of upper extremity (31.3+10.5 vs 39.9+8.5, p=0.013) and lower extremity (29+9.5 vs 43.9+9.6, p<0.001) were significantly shorter in AS patients with RLS than in AS patients without RLS.
In multivariate regresssion analysis, it was seen that independent parameters associated with RLS in AS patients were the presence of iron deficiency anemia (OR: 4.3, 95%CI: 1.6-11.4, p=0.001) and smoking (OR: 5.2, 95%CI: 1.8-15.2, p=0.004).
Conclusions Our findings indicate that RLS is commonly associated with AS. Possible causes include iron deficiency anemia, smoking and small fiber neuropathy. It is possible that many of AS patients with uncertain neurosensory symptoms and electrophysiologic abnormalities have previously unrecognized small fiber neuropathy.
Disclosure of Interest None declared