Table 1 Quality assessment of included studies
Studies | Selection | Comparability | Outcome | Total scores | |||||
|---|---|---|---|---|---|---|---|---|---|
| Â | Representativeness of the exposed group | Selection of the unexposed group | Ascertainment of exposure | Outcome of interest not present at start of study | Control for important factor or additional factor | Outcome assessment | Follow-up long enough for outcome to occur | Adequacy of follow-up of cohorts | Â |
Wang Qingtu, 2001 [45] | 1 | 1 | 1 | 1 | 2 | 1 | – | – | 7 |
Wang Jianshe, 2002 [16] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Wang Lan, 2004 [44] | 1 | 1 | 1 | 1 | – | 1 | 1 | 1 | 7 |
Wang Yuan, 2005 [43] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Gu Jie, 2006 [42] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Qian Yanhua, 2006 [41] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Fan Yi, 2007 [40] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Chen Jing1, 2007 [38] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Chen Jing2, 2007 [38] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Li Jijun1, 2007 [39] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Li Jijun2, 2007 [39] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Chen Hong, 2008 [37] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Liu Xia, 2008 [36] | 1 | 1 | 1 | 1 | – | 1 | 1 | 1 | 7 |
Liu Honge, 2009 [35] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Zhang Qingying, 2009 [34] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Zhu Yunxia, 2010 [32] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Yang Peifang, 2010 [33] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Yang Xiaomei, 2011 [30] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Zhang Weili, 2011 [31] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Huang Liu, 2012 [29] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Guo Zhen, 2013 [15] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Wang Ling, 2013 [28] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Hu Yali, 2013 [14] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Yin Yuzhu, 2013 [12] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Pan Calvin Q., 2013 [13] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
Zhang Lei, 2014 [11] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Wang Lina, 2014 [26] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Li Weiru, 2014 [25] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | Â | 9 |
Huang Dan, 2014 [27] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
Liu Cuiping, 2015 [10] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |