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Table 3 Subgroup analysis of relative risks for the association between insomnia and depression

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

  1. Abbreviations: BMI body mass index, dur duration criterion, day daytime consequences criterion, F female, M male, NA not available, SES socioeconomic status, Sd sleep difficulties criterion
  2. *Study population truly or somewhat representative of a community or population-based study defined as general population, and study population was sampled from a special population (such as population from a company, register patients, data from the health insurance company or health examination organization or pregnant), which defined as non-general populations