The dawn phenomenon does not occur in normal elderly subjects.

Area of Science:

• Endocrinology
• Metabolism
• Gerontology

Background:

• The dawn phenomenon is characterized by a morning rise in blood glucose.
• Aging is associated with progressive mild fasting hyperglycemia.
• The occurrence of the dawn phenomenon in healthy elderly individuals is not well-established.

Purpose of the Study:

• To investigate the presence of the dawn phenomenon in normal elderly subjects.
• To determine if the dawn phenomenon contributes to age-related fasting hyperglycemia.
• To examine the effects of physiological insulin on glucose metabolism in the elderly during dawn hours.

Main Methods:

• Paired euglycemic insulin clamp studies were conducted on healthy elderly subjects (n=5).
• The studies utilized [3H]glucose methodology to measure glucose production and disposal rates.
• Measurements were taken during dawn (0530-0800 h) and control (0930-1200 h) periods.

Main Results:

• Steady-state plasma insulin levels were not significantly different between dawn and control periods.
• Insulin clearance rates were significantly higher during the dawn study.
• Maximum glucose disposal rates and minimum hepatic glucose production (HGO) levels did not differ significantly.

Conclusions:

• The dawn phenomenon does not occur in healthy elderly subjects.
• Increased insulin clearance during the dawn period in the elderly does not lead to the dawn phenomenon.
• The dawn phenomenon is unlikely to be a significant contributor to age-related fasting hyperglycemia.