Table 2. Quality scores of included six cohort studies using Newcastle-Ottawa Scale.
| Selection | Comparabilityb | Outcome | Overall score | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Author | Cohort name | Representativeness of the exposed cohort | Selection of the non-exposed cohort | Ascertainment of exposure | Outcome of interest not present at start of study | Comparability of cohorts on the basis of the design or analysis | Assessment of outcome | Follow-up long enough for outcomes to occurc | Adequacy of follow-up of cohortsd | |||||
| Tamura et al
(2018) [18] |
Takayama Study | * | * | – | * | * | * | * | * | * | 8 | |||
| Inoue et al
(2009) [17] |
JPHC Study II | – | – | – | * | * | * | * | * | * | 6 | |||
| Ohishi et al
(2008) [16] |
Adult Health Studya | – | – | – | * | * | * | * | * | – | 5 | |||
| Kurozawa et al
(2005) [15] |
JACC Study | – | – | – | * | * | * | * | * | – | 5 | |||
| Shimazu et al
(2005) [14] |
Japan Miyagi Prefecture, Cohort 1 | * | * | – | * | * | * | * | – | – | 6 | |||
| Japan Miyagi Prefecture, Cohort 2 | * | * | – | * | * | * | * | – | – | 6 | ||||
Abbreviation: JACC, the Japan Collaborative Cohort; JPHC, the Japan Public Health Center-based Prospective.
aNested case-control study.
bA maximum of two stars can be assigned for the “Comparability” category. One star was awarded if the study provided risk estimates with controlling for age and sex, with an additional star awarded if it controlled for other potential confounders including alcohol intake and smoking status.
cA study with the follow-up of 10 years or longer was awarded one star.
dA study with the follow-up rate of 80% or higher was awarded one star.