Differential changes of autonomic nervous system function with age in man

Area of Science:

• Physiology
• Gerontology
• Neuroscience

Background:

• Autonomic nervous system (ANS) function is crucial for maintaining homeostasis.
• Aging is associated with various physiological changes, including potential alterations in ANS function.

Purpose of the Study:

• To investigate the relationship between aging and autonomic nervous system function.
• To assess cardiovascular and pupillary autonomic reflexes in relation to age.

Main Methods:

• Measured plasma norepinephrine and epinephrine levels.
• Assessed respiratory variation of heart rate and pupillary responses to light.
• Included 103 normal male subjects aged 19 to 82 years.

Main Results:

• Increased plasma norepinephrine and mean arterial blood pressure with age.
• Reduced respiratory variation of heart rate (parasympathetic activity) in older subjects.
• Diminished sympathetic and parasympathetic iris function in older subjects, indicated by pupil size and response latency.

Conclusions:

• Aging is associated with an increase in cardiovascular sympathetic activity and a decrease in cardiac parasympathetic activity.
• Both sympathetic and parasympathetic iris functions decline with age, consistent with generalized peripheral nerve aging.
• Compensatory ANS responses to age-related changes like decreased baroreceptor sensitivity may mask underlying functional deficits.