Table 4 Sleep parameters of nights with nightmares in frequent nightmare sufferers (NM) compared with matched nights of healthy controls (HC)

Sleep period time (min)

444.63 ± 58.20

461.36 ± 61.98

−0.652

0.522

0.28

Sleep efficiency (%)

84.73 ± 9.65

85.65 ± 6.64

−0.262

0.796

0.11

Sleep onset latency (min)

20.77 ± 13.55

15.364 ± 10.02

1.064

0.300

0.45

REM latency (min)

86.54 ± 42.78

95.04 ± 39.64

−0.483

0.634

0.21

REM density

21.68 ± 8.10

22.80 ± 7.00

−0.348

0.731

0.15

Number of awakenings

28.36 ± 11.38

28.73 ± 8.90

−0.083

0.467*

0.04

Number of REM periods

3.45 ± 1.29

3.27 ± 0.64

0.417

0.683

0.18

Arousal Index

10.63 ± 3.19

9.46 ± 1.21

1.130

0.140*

0.48

Awake%

11.02 ± 9.06

10.95 ± 6.07

0.022

0.983

0.01

Stage N1%

10.14 ± 3.19

8.24 ± 3.36

1.353

0.191

0.58

Stage N2%

44.89 ± 6.61

44.23 ± 7.02

0.227

0.823

0.10

Stage N3%

19.83 ± 6.86

21.22 ± 8.51

−0.423

0.677

0.18

Stage REM%

14.08 ± 3.85

15.32 ± 3.53

−0.786

0.441

0.34

Arousal index (REM only)

10.73 ± 5.15

12.09 ± 8.38

0.519

0.305*

0.22

Periodic leg movements

1.78 ± 5.91

1.18 ± 3.94

0.278

0.784

0.12