Postprandial hypotension in elderly subjects: spectral analysis of heart rate variability and electrogastrograms

In order to clarify the mechanism of postprandial hypotension in the elderly, the influence of gastric motility and autonomic nervous activity on hypotensive reactions after meals was investigated, using electrogastrograms (EGGs) and spectral analysis of heart rate variability.

EGGs, heart rate variability, blood pressure, and blood catecholamine levels before and after a meal were measured in 20 healthy young subjects (mean age, 25.6+/-5.6 years; young group) and in 20 healthy elderly subjects (mean age, 78.3+/-5.6 years; elderly group).

In the analysis of heart rate variability, no significant changes were observed in the low-frequency component (LF power), high-frequency component (HF power), or LF/HF ratio after the meal in the young group. In the other hand, the LF/HF ratio was significantly increased after the meal in the elderly group. In the EGG analysis, the peak power amplitudes after the meal were significantly increased compared with those before the meal in both groups. After the meal, the peak power amplitudes in the young group were significantly greater than those in the elderly group. The baseline blood noradrenaline level (before the meal) was higher in the elderly group than in the younger group, but the level of this catecholamine in the elderly group did not increase significantly after the meal.

It is suggested that the down-regulation of catecholamine may be one of the causes of postprandial hypotension in the elderly. The response to secreted catecholamine and the compensatory response to decreased blood flow in the systemic circulation were impaired in the elderly group, which finding may explain the high incidence of postprandial hypotension in the elderly subjects.