IRS1 and obstructive sleep apnea syndrome: Based on the subgroup analysis according to the severity of OSA (Table 5), allele frequencies of IRS1 [Gly972Arg] were 92% (Gly) and 8% (Arg) in the mild group, and 85% (Gly) and 15% (Arg) in the moderate group, and 76% (Gly) and 24% (Arg) in the severe group with a significant difference (p = 0.004), suggesting that patients with the ‘Gly’ allele were inclined to develop more severe OSA (p<0.05).