Noise stimulus in normal subjects: time-dependent blood pressure pattern assessment.

Environmental noise may have various effects on blood pressure. The aim of our study was to verify noise impact on blood pressure in normal young subjects, using the "white noise" stimulus. Thirty subjects (16 males and 14 females, median age 22 years) were studied. The presence of hypertension, hypertensive hereditibility and loss of acoustic acuity were criteria for exclusion. Noninvasive measurements of systolic and diastolic blood pressure at three-minute intervals were performed with an oscillometric system (Omega 1000, In Vivo Research), for each of four phases of the trial. After an initial rest phase (9 min) to avoid the patient's "alarm reaction," "white noise" with an intensity equal to 40, 100, and 40 adjusted decibels (dBa) was administered consecutively for 18 min (2nd phase), 9 min (3rd phase), and 18 min (4th phase), respectively. Preliminary analysis with standard statistical tools was not able to analyze the blood pressure patterns during the test. On the contrary, polygonal analysis, taking into account the "time-dependent" changes, showed that noise exposure (100 dBa) significantly increased systolic blood pressure in 22/30 subjects. However, systolic blood pressure rose only at the beginning of the 100 dBa exposure, indicating that stimulus changes rather than noise are key provoking factors in blood pressure increases.