“…We assessed the quality of included studies based on the NOS approach, 12 studies were regarded as high quality in case-control study, [ 7 , 19 , 21 , 23 , 24 , 27 , 28 , 30 , 34 , 38 – 40 ] and all the cohort studies were regarded as high quality with NOS >6. [ 3 , 8 , 9 , 25 , 26 , 32 , 33 , 35 – 37 ]…”