Table 2

 Weighted standardised mean differences in effect of Z drugs (treatment) or placebo on insomnia

Weighted mean effect size (95% CI)Homogeneity of effect sizes I2 (95% CI)
Within groupsBetween groups
No*TreatmentControlNo*Treatment v controlTreatmentControlTreatment v control
Primary outcome-sleep latency
PSG16−0.93 (−1.32 to −0.54)−0.39 (−0.54 to −0.23)22−0.36 (−0.57 to −0.16)89 (83.58 to 92.47)0 (0 to 77.60)41 (1.18 to 64.30)
Subjective4−0.67 (−1.30 to −0.03)−0.33 (−0.63 to −0.03)11−0.33 (−0.62 to −0.04)0 (0 to 49.26)0 (0 to 66.15)83 (70.98 to 90.05)
Secondary outcomes
Wake after sleep onset (PSG)2−0.52 (−1.40 to 0.36)−0.29 (−0.67 to −0.08)3−0.24 (−0.72 to 0.24)83 (29.36 to 95.94)50 (0 to 87.35)0 (0 to 93.84)
No of awakenings (PSG)2−0.36 (−1.28 to 0.56)−0.21 (−0.60 to 0.17)4−0.33 (−0.80 to 0.14)91 (70 to 97.57)0 (0 to 99.67)65 (0 to 88.10)
No of awakenings (subjective)2−0.91 (−1.90 to 0.09)−0.28 (−0.66 to 0.10)6−0.06 (−0.42 to 0.29)87 (47.31 to 96.63)36 (0 to 79.25)85 (69 to 92.67)
Total sleep time (PSG)21.06 (−1.37 to 3.49)0.65 (−0.67 to 1.98)20.41 (−0.51 to 1.32)74 (0 to 94.19)42 (0 to 83.14)0
Sleep efficiency (PSG)20.52 (−1.23 to 2.28)0 (−0.59 to 0.59)50.59 (−0.12 to 1.29)54 (0 to 88.82)00 (0 to 75.02)
Total sleep time (subjective)070.45 (−0.08 to 0.98)0 (0 to 71.12)
Sleep quality (subjective)040.30 (−0.32 to 0.92)0 (0 to 71.13)
Wake after sleep onset (subjective)01−0.16 (−0.60 to 0.28)

PSG=polysomnographic.

*No of comparisons.