Daily noise duration influences cardiovascular responses

Area of Science:

• Environmental Health
• Cardiovascular Physiology
• Toxicology

Background:

• Non-auditory health effects of noise exposure are increasingly recognized.
• Previous research suggests a link between intense noise and altered blood pressure regulation.
• A dose-response relationship between noise exposure and blood pressure is hypothesized.

Purpose of the Study:

• To investigate the long-term dose-response relationship between intense noise exposure and blood pressure regulation.
• To determine the effect of interposed rest sessions on heart rate (HR) and blood pressure (BP) during chronic noise exposure.
• To examine the persistence of noise-induced blood pressure changes after noise cessation.

Main Methods:

• Two adult female macaque monkeys (Macaca fascicularis) were exposed to tape-recorded industrial noise (pile-driver impacts, construction noises) for 4-hr or 8-hr daily sessions over 97 days.
• Noise exposure levels were Leq24 = 86.6 dB for 4-hr sessions and Leq24 = 89.6 dB for 8-hr sessions.
• Indwelling cannulas were used to monitor mean arterial pressure (MAP) and heart rate (HR).

Main Results:

• Mean arterial pressure (MAP) increased by 8.2% during 4-hr and 16.5% during 8-hr noise exposure sessions compared to pre-exposure levels.
• A doubling of noise energy resulted in a near-doubling of MAP increase in the exposed monkeys.
• Heart rate (HR) returned to baseline levels upon noise termination, while MAP remained significantly elevated, indicating persistent effects.

Conclusions:

• Intense noise exposure establishes a long-term dose-response relationship with elevated blood pressure.
• Noise-induced hypertension shows persistence even after noise cessation, highlighting significant non-auditory health risks.
• The study supports the "law" of Initial Values, where baseline blood pressure influences the percentage of BP increase under noise stress.