Table 4 Newcastle-Ottawa Quality Assessment Scale

Comparability

Study

Representativeness of sample

Sample size

Non-respondents

Ascertainment of exposure

Confounding factors controlled

Assessment of the outcome

Quality

Bailey 2013 [29]

1

0

1

2

0

1

Poor

Burke 2010 [33]

0

0

0

2

0

1

Poor

Cowan 1985 [27]^a

1

0

0

2

1

1

Fair

Murphy 1988 [28]

1

0

0

2

1

1

Fair

Fullerton 1999 [36]

1

0

0

2

1

1

Fair

Heeke 2017 [38]

0

0

0

2

2

1

Fair

Kristensen 2010 [40]

1

0

1

2

1

1

Good

Levi-Belz 2015 [42]

1

0

0

2

0

1

Poor

Levi-Belz 2019 [43]

1

0

0

2

2

1

Good

Li 2015 [44]

1

0

0

2

0

1

Poor

Oexle 2019 [45]

0

0

1

2

2

1

Good

Rheingold 2015 [47]

1

0

0

2

1

1

Good

Spino 2016 [48]

0

0

0

2

0

1

Poor

Sprang 1998 [50]

1

0

0

2

2

1

Good

Xu 2017 [52]

1

0

0

2

1

1

Good

Comparability

Representativeness

Selection of non-exposed cohort

Ascertainment of exposure

Outcome of interest not present at start of study

Comparability of cohorts

Assessment of outcome

Follow-up long enough for outcome to occur

Adequacy of follow-up

Quality

Bottomley 2017 [31]

0

n/a

1

0

1

1

1

1

Fair