Fig. 3

a Relationship between flow-mediated dilatation (FMD) of the brachial artery and age. Line indicates FMD = 9 %, suggesting the lower limit of FMD. b Relationship between extrinsic nitric oxide donor-induced dilatation (NID) of the brachial artery and age. Line indicates NID = 12 %, suggesting the lower limit of NID