Four studies evaluated the rs180126 CLOCK gene polymorphisms in 1261 participants with MetS risk factors and 1129 control participants [21,24,27,31], while only two studies evaluated rs6850524 in CLOCK [22,29] and rs7950226 in BMAL1 gene [25,31] with 651 and 1835 participants with MetS risk factors and 975 and 2011 control participants, respectively. Here, CLOCK is linked to metabolic syndrome.