The Effect of Glucose Tolerance on Central and Brachial Pressure in Elderly People

To the Editor: Central blood pressure (BP), brachial BP, and augmentation index decreased after an oral glucose tolerance test (OGTT); the magnitude of decrease in central BP was higher than that in the brachial BP in elderly people. The magnitude of decrease in central systolic BP (SBP) and brachial SBP after an OGTT increased in a stepwise fashion across the brachial mean BP (MBP) before the OGTT. Various kinds of daily orthostatic change, exercise, and eating affect the cardiovascular system.1-3 Central hemodynamic variables are independently associated with organ damage and incident cardiovascular disease.4, 5 Central BP may be different from that measured on the arm. As for the BP decrease caused by standing up, the measurement of brachial BP suggests the possibility of a negligible decrease in brachial BP compared with that in the central BP.2 Postprandial hypotension (PPH) is recognized as an important clinical problem in elderly people.3 Although assessment of PPH in elderly people is important, changes in central BP after food consumption have not been studied. Thus, it was hypothesized that central BP changes are different from brachial BP changes. To clarify this, brachial and central BP before and after a 75-g OGTT in an elderly population were examined. Subject's characteristics are listed in Table 1. Mean age was 80.5, and 65.7% were female. Brachial SBP and diastolic BP (DBP) after the OGTT were significantly lower than before the OGTT (brachial SBP: 132.1 ± 20.2 vs 126.6 ± 18.6 mmHg, P<.01; DBP 69.4 ± 12.0 vs 65.5 ± 11.2 mmHg, P<.01). SBP2 and AI after the OGTT were significantly lower than before the OGTT (SBP2 125.2 ± 20.1 vs 118.4 ± 18.6 mmHg, P<.01; AI 92.6 ± 11.6 vs 89.2 ± 13.3%, P=.02). No significant difference was observed between pulse pressure and pulse rate before and after the OGTT. The magnitude of decrease in SBP2 after the OGTT was significantly greater than in brachial SBP (−6.8 ± 16.3 vs −5.5 ± 15.9 mmHg, P=.01). The frequency of participants having only SBP2 decrease 20 mmHg or more after the OGTT was 8.2% (n=6). Stepwise regression analysis revealed that brachial MBP before the OGTT was an independent determinant of brachial SBP and SBP2 changes before and after the OGTT. The participants were divided into four quartile groups according to brachial MBP before the OGTT. The magnitude of decrease in brachial SBP and SBP2 after the OGTT increased in a stepwise fashion across the brachial MBP before the OGTT (P<.01; Table 1). This study found that central BP, brachial BP, and AI decreased after an OGTT. The magnitude of decrease in central BP was higher than of brachial BP. Radial AI is the ratio of the augmented pressure, which is generated by the reflection wave from the lower body, to the forward pressure.8 Therefore, the magnitude of the decrease in the augmented pressure supports the theory that the predominant constituent of the pressure decrease after an OGTT was an induced reflection wave reduction from the lower body. The magnitude of decrease in central and brachial SBP after the OGTT increased in a stepwise fashion across brachial MBP before the OGTT. The decreased distensibility of the aorta and the excessive dilatation in the splanchnic artery may affect the impedance matching between the aorta and splanchnic artery.9 A loss of the proximal reflecting site at the interface between the aorta and splanchnic arteries may explain why there is a reduction in central BP with a stepwise increase in brachial MBP before the OGTT. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this letter. Author Contributions: All the authors contributed to design, methods, data analysis, and preparation of this letter. Sponsor's Role: None.