Table 3 Single items of PSQI and PSQI categories of the study population at baseline and after 31 days of active stage of VLCKD

Sleep quality

1.29 ± 0.89

0.92 ± 0.80

< 0.001

Sleep onset latency

1.16 ± 1.01

0.82 ± 0.91

< 0.001

Sleep duration

1.24 ± 1.06

0.77 ± 0.91

< 0.001

Sleep efficiency

0.99 ± 1.08

0.51 ± 0.79

< 0.001

Sleep disturbance

1.37 ± 0.84

1.05 ± 0.65

< 0.001

Hypnotic drugs

0.51 ± 1.02

0.18 ± 0.62

< 0.001

Daytime dysfunction

1.17 ± 1.03

0.72 ± 0.80

< 0.001

PSQI categories

 Good sleepers (n, %)

139, 42.9%

211, 65.1%

χ² = 31.32

 Poor sleepers (n, %)

185, 57.1%

113, 34.9%

p < 0.001