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Sex-specific risk estimates of cardiovascular disease risk from age 45 to 85 years in relation to heart rate variability, ARIC, 1987–2013. SDNN, standard deviation of all normal-to-normal RR intervals; RMSSD, root mean square of successive differences of successive RR intervals; MeanNN, mean of all normal-to-normal RR intervals; LF, low frequency power; and HF, high frequency power.
