Fig. 4From: An examination of sleep spindle metrics in the Sleep Heart Health Study: superiority of automated spindle detection over total sigma power in assessing age-related spindle declineAÂ Population NREM2 sigma power and BÂ spindle sigma power as a function of age. CÂ Mean N2 sigma power and DÂ spindle sigma power are significantly reduced from baseline to follow up a minimum of 3Â years laterBack to article page