Table 1. Quality of included studies assessed using the Cambridge Quality Checklist.

Reference	Checklist for correlate	Checklist for risk factor	Checklist for casual risk factor	Overall score
Djaladat et al [16]	2	3	5	10/15
Isitmangil et al [17]	2	3	5	10/15
Gubin et al [18]	1	2	2	5/15
Golomb et al [19]	1	1	2	4/15
Oshinsky et al [20]	1	2	2	5/15
Fichorova et al [21]	1	1	2	4/15