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Table 2 Subgroup meta-analysis and analysis of heterogeneity

From: Systematic review and meta-analysis of the relationship between sleep disorders and suicidal behaviour in patients with depression

Subgroup No. of studies No. of subjects OR (95%CI) Heterogeneity P value
I2(%) P value
Year of publication
 1997 ~  2010 10 166,949 2.53 (1.75 3.66) 76.8 <  0.001 <  0.001
 2010 ~  2019 8 31,944 2.10 (0.80 5.53) 99.5 <  0.001 0.134
Study design
 Retrospective 6 171,176 1.79 (1.33 2.42) 83.1 <  0.001 <  0.001
 Prospective 6 4856 2.25 (1.39 3.64) 75.3 0.001 0.001
 Cross-sectional 6 22,861 2.45 (0.79 7.61) 98.9 <  0.001 0.122
Sample size
 < 1000 11 2234 2.99 (1.28 6.98) 99.2 <  0.001 0.011
 > 1000 7 196,659 1.50 (1.24 1.81) 53.8 0.043 <  0.001
Age of subjects
 Mean < 40 12 189,712 2.75 (1.26 6.03) 99.4 <  0.001 0.011
 Mean > 40 6 9181 1.81 (1.30 2.51) 73.4 0.002 <  0.001
Diagnostic criteria
 ICD-10 2 1541 2.13 (1.10 4.12) 43.2 0.185 0.025
 DSM-III-R 4 2681 4.80 (2.90 7.67) 0 0.720 <  0.001
 DSM-IV 11 174,541 2.11 (0.96 4.65) 99.4 <  0.001 0.063
 CES-D 1 20,130 1.12 (0.92 1.37) 0.265
Diagnostic outcome
 Major depression 12 5336 2.92(1.42 5.98) 97.5 <  0.001 0.003
 Depression 6 193,557 1.41(1.14 1.73) 75.6 0.001 0.001
Sleep disorder type
 Insomnia 12 172,759 2.29 (1.69 3.10) 86.1 <  0.001 <  0.001
 Nightmares 3 582 4.47 (2.00 9.97) 0 0.490 <  0.001
 Hypersomnia 3 2914 2.19 (0.77 6.21) 93.0 <  0.001 0.140
 Other 7 27,144 2.41 (0.80 7.24) 99.6 <  0.001 0.117
Suicidal behavior type
 Suicidal ideation 13 194,419 2.32 (1.11 4.88) 99.2 <  0.001 0.026
 Suicide attempts 7 193,834 2.41 (1.45 4.02) 87.7 <  0.001 0.001
 Completed suicide 2 163,668 1.24 (1.00 1.53) 0 0.445 0.050
 Other 2 225 4.19 (2.82 6.21) 0 0.654 <  0.001
  1. OR Odds ratio, ICD-10 International classification of diseases, tenth revision, DSM The diagnostic and statistical manual of mental disorders, CES-D Center for epidemiology scale for depression