From: Insomnia and the risk of depression: a meta-analysis of prospective cohort studies
 | No of studies | RR (95 % CI) | I 2 (%) | P value for heterogeneity | P value between groups |
---|---|---|---|---|---|
Mean age at baseline, y | |||||
 <60 | 22 | 2.50 (1.96, 3.20) | 94.70 | <0.001 | 0.31 |
 ≥60 | 12 | 1.87 (1.47, 2.37) | 80.70 | <0.001 | |
Sex | |||||
 Male | 3 | 1.46 (1.13, 1.88) | 26.70 | 0.256 | 0.48 |
 Female | 3 | 1.96 (1.05, 3.66) | 73.50 | <0.001 | |
 Mixed | 28 | 2.41 (1.97, .95) | 92.80 | <0.001 | |
Study location | |||||
 USA | 14 | 3.13 (2.03, 4.85) | 89.80 | <0.001 | 0.17 |
 Europe | 14 | 1.73 (1.43, 2.09) | 88.50 | <0.001 | |
 Asia | 4 | 2.27 (1.22, 4.21) | 90.40 | <0.001 | |
 Australia | 2 | 1.79 (0.90, 3.54) | 95.90 | <0.001 | |
Source of participants* | |||||
 General population | 25 | 2.34 (1.85, 2.96) | 94.00 | <0.001 | 0.75 |
 Non-general population | 9 | 2.05 (1.53, 2.74) | 78.70 | <0.001 | |
Insomnia definition | |||||
 Sd, dur and day | 11 | 2.90 (1.78, 4.74) | 92.70 | <0.001 | 0.37 |
 Sd and dur | 10 | 2.21 (1.50, 3.25) | 90.30 | <0.001 | |
 Sd | 13 | 1.87 (1.53, 2.29) | 87.70 | <0.001 | |
Type of depression measure | |||||
 Self-reported scales | 17 | 2.20 (1.70, 2.86) | 94.10 | <0.001 | 0.63 |
 Physician diagnosis | 15 | 2.27 (1.67, 3.09) | 91.80 | <0.001 | |
 Combined | 2 | 3.89 (1.73, 8.74) | 0.00 | 0.438 | |
Follow-up duration, y | |||||
 <5 | 22 | 2.34 (1.84, 2.97) | 93.60 | <0.001 | 0.77 |
 5–10 | 8 | 2.37 (1.73, 3.25) | 82.30 | <0.001 | |
 >10 | 4 | 1.88 (1.52, 2.32) | 54.60 | 0.086 | |
Sample size | |||||
 <5000 | 26 | 2.01 (1.66, 2.44) | 86.50 | <0.001 | 0.10 |
 ≥5000 | 8 | 3.12 (2.11, 4.62) | 96.40 | <0.001 | |
Study quality | |||||
 Score >7 | 8 | 2.06 (1.60, 2.63) | 88.60 | <0.001 | 0.70 |
 Score ≤ 7 | 26 | 2.36 (1.83, 3.03) | 93.00 | <0.001 | |
Publication year | |||||
 Before 2010 | 19 | 2.63 (1.95, 3.55) | 88.20 | <0.001 | 0.21 |
 2010–2014 | 15 | 1.94 (1.53, 2.45) | 94.62 | <0.001 | |
Statistical model | |||||
 Unadjusted | 5 | 1.78 (1.29, 2.47) | 56.00 | 0.078 | 0.75 |
 Adjusted | 29 | 2.31 (1.90, 2.81) | 93.40 | <0.001 | |
Controlling age in models | |||||
 Yes | 21 | 2.64 (2.04, 3.42) | 92.30 | <0.001 | 0.09 |
 No | 13 | 1.75 (1.33, 2.31) | 92.50 | <0.001 | |
Controlling SES in models | |||||
 Yes | 17 | 2.34 (1.81, 3.03) | 95.60 | <0.001 | 0.78 |
 No | 17 | 2.15 (1.74, 2.65) | 71.60 | <0.001 | |
Controlling smoking status in models | |||||
 Yes | 7 | 2.10 (1.45, 3.06) | 89.80 | <0.001 | 0.75 |
 No | 27 | 2.32 (1.88, 2.87) | 93.30 | <0.001 | |
Controlling alcohol intake in models | |||||
 Yes | 9 | 2.47 (1.75, 3.48) | 90.90 | <0.001 | 0.69 |
 No | 25 | 2.19 (1.78, 2.69) | 92.00 | <0.001 | |
Controlling BMI in models | |||||
 Yes | 5 | 2.19 (1.57, 3.06) | 85.30 | <0.001 | 0.94 |
 No | 29 | 2.28 (1.87, 2.78) | 92.30 | <0.001 |