Table 2

Correlation coefficients for sleep spindle/σ activity in the cross-sectional sample (above diagonal) and the longitudinal sample (below diagonal)

Spindle densitySpindle frequencyFast spindle percentSpindle powerσ power
Spindle density---0.2050.2630.5530.311
Spindle frequency0.286---0.931−0.120−0.104
Fast spindle percent0.3490.564---−0.061−0.106
Spindle power0.4710.1910.248---0.628
σ power0.5530.2620.2250.671---
  • Data are Pearson correlation coefficients. For the cross-sectional sample, the correlation coefficients for spindle density (#/min), spindle frequency (Hz), fast spindle percent (%), and spindle and σ power (μV2) were determined. For the longitudinal sample, the correlation coefficients for the percent change in each spindle metric from baseline (ages 5–12) to follow-up (ages 12–22) were calculated.