highly significantP = 0.001
However, there were highly significant correlations of L5 activity with RRI (ρ = −0.53, P = 0.001) and LF/HF (ρ = 0.44, P = 0.007) during L5 in the total participants indicating that dominance of the sympathetic system relative to the parasympathetic system is associated with higher activity during sleep.