Noise-induced Hearing Loss: Continuous versus Impact/impulse Noise.

Background: Impact/impulse and continuous noise are two main causes of noise-induced hearing loss (NIHL) in workplaces. The aim of this study was to compare the effects of impulse/impact noise and continuous noise on hearing status. Methods: In this study, 259 workers referred to the occupational medicine clinic of Shahid Rahnemoun hospital, Yazd, Iran, entered the study and were divided into two groups: with exposure to impact/impulse noise and with exposure to continuous noise. Hearing thresholds were measured and compared between the two groups by pure-tone audiometry (PTA). The frequency of hearing loss and audiometric notch according to the results of PTA was compared between the two groups. Data were analyzed by SPSS (ver. 16) using Student's t-test, Chi-square test, and Mann-Whitney U test. Results: Hearing thresholds were significantly higher at all frequencies in the impact noise group. The hearing threshold at 6000 Hz was higher than other frequencies in both groups. The frequency of hearing loss at high frequencies was higher in the impact group. The frequency of audiometric notch was not significantly different between the two groups. Conclusions: The results of this study showed that hearing loss after exposure to impact/impulse noise is probably more frequent and more severe than exposure to continuous noise, but the pattern of hearing loss is similar in both types of noise exposure.

Hearing Thresholds Changes after MRI 1.5T of Head and Neck.

INTRODUCTION: Exposure to high intensity noise produced by MRI is a cause for concern. This study was conducted to determine the temporary and permanent effects of exposure to noise created by performing MRI on the hearing threshold of the subjects using conventional and extended high frequency audiometry. METHODS: This semiexperimental study was performed on 35 patients referred to Shahid Rahnemoun Hospital for head and neck MRI due to different clinical conditions. The hearing threshold of patients was measured before, immediately after, and 24 hours after performing 1.5 Tesla MRI using conventional and extended high frequency audiometry. SPSS version 18 was used to compare the mean hearing thresholds before and after MRI using paired T test and repeated measures analysis. RESULTS: Comparison of auditory thresholds in conventional and extended high frequencies before and immediately after MRI showed a significant shift at 4 KHz (P = 0.008 and P = 0.08 for right and left ears), 6 KHz (P = 0.03 and P = 0.01 for right and left ears), and 14 KHz (P =0.03 and P = 0.31 for right and left ears). However, there was no significant difference between audiometric thresholds before and 24 hours after MRI. CONCLUSION: Noise due to 1.5 Tesla MRI can only cause transient threshold shift.

Comparison of growth parameters of 5-year-old singleton children born in assisted versus natural conception.

INTRODUCTION: At present, about 1% of newborns are delivered through assisted reproductive technologies (ART) worldwide. This study aimed to evaluate and compare the growth parameters of children born in assisted and natural conception at 5 years of age. MATERIALS AND METHODS: In a cross-sectional case control study, weight, height and head circumference of 5-year old children were assessed. The case group consisted of term, singleton babies who were products of ART in the Center for Infertility of Shahid Sadoughi University, Yazd, Iran in 2005. The control group consisted of term, fi rst child, singleton and spontaneously conceived 5-year-old children who were referred for vaccination to primary health care center of Shahid Akbari in 2010. RESULTS: Fifty-eight girls (47.5%) and 64 boys (52.5%) "with equal numbers in each of the 2 groups" were evaluated. Sex distribution, mean ages of fathers and mothers were not statistically significant different in both groups. Children born after ART tend to have lower birth weight, smaller birth head circumference and lower weight at 5 years of age. Having low birth weight (<2500 g), being underweight and having short stature at the age of 5 were more common in babies born through ART. CONCLUSION: Growth retardation is more prevalent in babies born through ART. Thus, growth assessment, parents' knowledge about child physical development, and timely and accurate follow-up of these children are necessary for early detection of any growth disorders.