Table 2 NOS for Cross-sectional and Cohort studies Quality Assessment using the Newcastle-Ottawa Scale
From: The association between headache and low back pain: a systematic review
CROSS-SECTIONAL STUDIES | Selection | Comparability | Outcomes | TOTAL (maximum 10✯) | Overall Quality Assessment (AHRQ standards) | |||||
Representiveness of exposed cohort | Sample Size | Non-respondents | Ascertainment of the exposure (risk factor) | Assessment of outcomes | Statistical test | |||||
Child and Adolescent Studies | ||||||||||
 Ghandour et al., 2004 [15] | ✯ | – | ✯ | ✯ | ✯✯ | ✯✯ | ✯ | 8✯ | Good | |
 Sjolie et al., 2002 [16] | ✯ | – | ✯ | ✯ | ✯✯ | ✯ | ✯ | 7✯ | Good | |
 Swain 2014 [17] | ✯ | ✯ | – | ✯ | ✯✯ | ✯ | ✯ | 7✯ | Good | |
Adult Studies | ||||||||||
 Ashina et al. 2018 [18] | ✯ | – | ✯ | ✯✯ | ✯✯ | ✯ | ✯ | 8✯ | Good | |
 Bejia et al. 2005 [19] | ✯ | – | – | ✯ | ✯ | ✯ | ✯ | 5✯ | Poor | |
 Bener 2015 [20] | ✯ | ✯ | ✯ | ✯ | ✯ | ✯ | ✯ | 7✯ | Good | |
 Yoon 2013 [10] | ✯ | – | – | ✯✯ | ✯✯ | ✯ | ✯ | 7✯ | Good | |
Older Adult Studies | ||||||||||
 Ahangar 2016 [21] | – | ✯ | – | – | ✯✯ | ✯ | ✯ | 5✯ | Poor | |
Twin Studies | ||||||||||
 Hartvigsen et al., 2004 (Hartvigsen et al., 2003) [22, 23] | ✯ | ✯ | ✯ | ✯ | ✯✯ | ✯ | ✯ | 8✯ | Good | |
 Hestbaek et al., 2004 [24] | ✯ | – | – | ✯ | ✯ | ✯ | ✯ | 5✯ | Fair | |
 Schur 2007 [25] | ✯ | – | – | ✯ | ✯ | ✯ | ✯ | 5✯ | Fair | |
COHORT STUDIES | Selection | Comparability | Outcomes | TOTAL (maximum 9✯) | Overall Quality Assessment (AHRQ standards) | |||||
Representiveness of exposed cohort | Selection of non-exposed cohort | Ascertainment of exposure | Outcome not present at the start of the study | Assessment of outcomes | Length of follow-up | Adequacy of follow-up | ||||
Child and Adolescent Studies | ||||||||||
 Jones et al., 2003 [26] | ✯ | ✯ | – | ✯ | ✯ | ✯ | ✯ | ✯ | 7✯ | Good |
Adult Studies | ||||||||||
 Angst et al. 2017 [27] | ✯ | ✯ | ✯ | ✯ | ✯✯ | ✯ | ✯ | ✯ | 9✯ | Good |
 Hestbaek et al., 2006 [28] | ✯ | ✯ | – | ✯ | ✯✯ | ✯ | ✯ | ✯ | 8✯ | Good |