Oral glucose tolerance test reduces arterial baroreflex sensitivity in older adults

Abstract

Although postprandial decreases in blood pressure are a common cause of syncope in the older adult population, the postprandial effects of the oral glucose tolerance test on blood pressure and the arterial baroreflex remain poorly characterized in older adults. Therefore, arterial blood pressure and the arterial baroreflex were studied in 19 healthy older adults (mean age 71.7 +/- 1.1 years) who were given a standardized oral glucose load (75 g) or an isovolumetric sham drink during 2 separate sessions. All measures were taken for 120 min after treatment. Baroreflex function was assessed by using the spontaneous baroreflex method (baroreflex sensitivity, BRS). Subjects demonstrated a decrease in BRS after oral glucose that was not seen in the placebo session (two-way analysis of variance, p = 0.04). There was no significant change in systolic, mean, or diastolic blood pressure; together with a drop in BRS, this resulted in a significant tachycardia post glucose (two-way analysis of variance, p < 0.001). We conclude that healthy older adults can successfully maintain blood pressure during an oral glucose tolerance test despite a decrease in arterial BRS. Decreased BRS resulted in a tachycardic response to glucose.

Baroreflex function and postprandial hypotension in older adults

“…The acute effects of a meal on baroreflex function are also very poorly studied, but could be a potential explanation for the PPH response. Previous work in older adults has shown that a large glucose dose (in the setting of an oral glucose tolerance test in older adults without diabetes) results in significant acute baroreflex dysfunction [32]. The current study (which used a standardized meal, not glucose), while it did not demonstrate any postprandial change in BRS, did demonstrate a postprandial reduction in baroreflex effectiveness in PPH subjects, which to our knowledge is a novel finding.…”

Autonomic, Cardiovascular, and Respiratory Responses to Hyperglycemic Stimulus in Healthy Subjects

“…Previous studies on the ACR response of healthy subjects to hyperglycemia have in common that: hyperglycemia has been provoked by either glucose [2,3] or meal ingestion [4,6]; to assess its effects, spectral measures of CVV have been used more frequently than microneurography, always assuming stationary signals, which implies the use of ad hoc spectral analysis techniques [1][2][3][4]6]; and have attributed the autonomic effects to insulin [1,6]. The following effects of hyperglycemia on ACR measures have been reported: HR increment [1,3,4,7] or no change [2]; AP increase [1,6], no change [2] or decrease [3]; sympathetic activity increase [1,3,6,8] or no change [2]; vagal activity increase [3], decrease [4] or no change [1,2]; and BRS decrease [1,3,7]. Therefore, the reported ACR effects of hyperglycemia are equivocal; however, most authors consider the sympathoexcitatory pressor effect to be the most relevant one [1,6,8], notion that contrasts with the dynamic and integrative mechanism supported by our findings, consisting in: vagal activity inhibition (Fig.…”

Arterial stiffness and the response to carotid sinus massage in older adults

“…Arterial baroreflex function was measured by the sequence method, which provides a measure of baroreflex sensitivity (BRS, in ms/mmHg) as previously described (18). 20 minutes of electrocardiogram and Finometer data was examined using a custom-written software program (Matlab Release 13, 2008) for progressive increases/decreases in both systolic blood pressure (SBP) and RR-interval (RRI).…”