Ankle-brachial index and peripheral artery disease are not related to restless legs syndrome

Our aim was to investigate the relationship between impaired peripheral arterial circulation as measured by ankle-brachial index (ABI) and restless legs syndrome (RLS) in the general population.

Data are derived from three independent, German population-based, prospective studies: the control sample of BiDirect (N = 966), the second follow-up of SHIP (N = 2333), and a subsample of SHIP-Trend (N = 1269). RLS was assessed with questions based on the RLS minimal criteria. ABI was measured with an automated method in BiDirect and with Doppler ultrasound in both SHIP studies. An ABI score below 0.9 was indicative of peripheral arterial disease (PAD). Co-morbidities, medications and behavioural factors were self-reported. Additional measurements included body mass index and haemoglobin from blood serum. For BiDirect, a follow-up with identical methodology was performed after a median of 2.5 years.

In cross-sectional analyses, decreased ABI was not significantly associated with RLS as outcome in multivariable logistic regression models adjusted for several potential confounders (BiDirect: odds ratio (OR) = 1.07 for a -0.1 change in ABI, 95% confidence interval (CI): 0.81-1.42, p = 0.62; SHIP-2: OR = 0.99, CI: 0.85-1.16, p = 0.94; SHIP-Trend: OR = 0.99, CI: 0.87-1.13, p = 0.88). Similar non-significant results were achieved using PAD (instead of ABI) as an independent variable. In BiDirect, baseline ABI was not a significant predictor of incident RLS in longitudinal analysis (OR = 0.77, CI: 0.53-1.12, p = 0.17).

Results from three independent studies suggest that reduced ABI is not a risk factor for RLS in the general population.