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Table 2 Quality assessment of studiesa

From: Insomnia and the risk of depression: a meta-analysis of prospective cohort studies

Study source Selection Comparability Exposure Total score
Representativeness of the exposed cohort Selection of the non- exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at start of study Comparability of cohorts on the basis of the design or analysis Assessment of outcome Was follow-up long enough for outcomes to occur (> = 5 years) Adequacy of follow up of cohorts (>80 %)
Ford and Kamerow [9] 1 1 1 1 1 1 0 0 6
Brabbins et al. [33] 1 1 1 1 0 1 0 0 5
Breslau et al. [34] 1 1 1 1 1 1 0 1 7
Chang et al. [18] 1 1 1 1 2 1 1 1 9
Weissman et al. [10] 1 1 1 1 1 1 0 0 6
Foley et al. [35] 1 1 1 1 0 1 0 0 5
Johnson et al. [36] 1 1 0 1 1 1 1 1 7
Mallon et al. [37] 1 1 0 1 1 1 1 0 6
Roberts et al. [17] 1 1 0 1 0 1 0 1 5
Roberts et al. [38] 1 1 0 1 2 1 0 0 6
Hein et al. [39] 0 1 1 1 0 1 1 1 6
Perlis et al. [40] 0 1 1 1 0 1 0 0 4
Morphy et al. [41] 1 1 1 1 2 1 0 0 7
Buysse et al. [20] 1 1 1 1 1 1 1 0 7
Cho et al. [19] 1 1 1 1 2 1 0 1 8
Jansson-Fröjmark and Lindblom [42] 1 1 1 1 1 1 0 1 7
Roane and Taylor [23] 1 1 1 1 0 1 1 0 5
Kim et al. [21] 1 1 1 1 2 1 0 0 7
Szklo-Coxe et al. [22] 1 1 1 1 1 1 0 0 6
Yokoyama et al. [43] 1 1 1 1 2 1 0 0 7
Jaussent et al. [45] 1 1 1 1 2 1 0 0 7
Almeida et al. [44] 1 1 1 1 2 1 1 0 8
Marques et al. [46] 0 1 0 1 1 1 0 0 4
Skapinakis et al. [53] 1 1 1 1 2 1 0 0 7
Salo et al. [49] 1 1 1 1 2 1 0 1 8
Suh et al. [54] 1 1 1 1 2 1 1 1 9
Paudel et al. [52] 1 1 1 1 2 1 0 0 7
Campbell et al. [50] 1 1 1 1 2 1 1 1 9
Jackson et al. [55] 1 1 1 1 1 1 1 1 8
Sivertsen et al. [56] 1 1 1 1 2 1 1 1 9
Okajima et al. [48] 1 1 1 1 1 1 0 0 6
Thomée et al. [47] 0 1 1 1 1 1 0 0 5
Gehrman et al. [51] 0 1 1 1 2 1 1 0 7
Dørheim et al. [32] 0 1 1 0 0 1 0 0 3
  1. aThe study quality was assessed according to the Newcastle Ottawa Quality assessment scale for cohort studies. This scale awards a maximum of 9 points to each study: 4 for selection, 2 for comparability, and 3 for assessment of outcomes (for cohort study). 1 = “Yes”, 0 = “No”, “Unable to determine” or “Not available”