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.

Effect of Combined Exposure to Noise and Vibration on Hearing.

AIM: This study was conducted to examine the effect(s) of combined exposure to whole-body vibration (WBV) and noise in railway workers. METHODS: In this historical cohort study, train drivers with combined exposure to WBV and impermissible noise as the case group (n = 85) and shunters with just exposure to impermissible noise as the control group (n = 30) were recruited. The hearing threshold at the conventional audiometric frequencies was measured in both the groups, and the standard threshold shift (STS) and hearing threshold shift at higher frequencies were calculated. Data were analyzed by SPSS version 20 using t-test, Chi-square, and paired t-test. RESULTS: There was no significant difference between the groups for age of participants as well as work duration and body mass index. Increased hearing threshold was most frequently observed at 3000, 4000, and 6000 Hz. STS and hearing threshold shift at high frequencies were observed at 6.0% and 3.3%, and 8.2% and 26.7% in train drivers and shunters in the left ear, respectively, but these were not statistically significant. CONCLUSION: Despite the unauthorized exposure to noise and WBV of train drivers, the STS and hearing threshold shift at higher frequencies were not more prevalent compared with the shunters who were exposed only to impermissible noise levels; hence, no association was found between noise and vibration in this study.

Effect of vitamin D on HbA1c levels of children and adolescents with diabetes mellitus type 1.

BACKGROUND: Studies show the relationship between vitamin D deficiency and glucose metabolism disorders. The aim of this study was the evaluation of the effect of vitamin D administration in management of diabetes mellitus type 1 (T1D). METHODS: We evaluated the effect of supplementation with vitamin D on HbA1c levels of children and adolescents with T1D. In this before-after study, 70 subjects with T1D were enrolled. Fasting serum 25-hydroxyvitamin D, calcium, phosphate, alkaline phosphatase, glucose and HbA1c were measured at the initiation and after the administration of 50,000 IU of vitamin D3 biweekly for 3 months. The results were then compared using paired t-test. Between 70 patients, five patients were excluded from the study because they did not completed the study and finally 65 subjects finished the study. RESULTS: Sixty-five patients including 35 children and 30 adolescents were recruited. Forty-three (66.1%) subjects had vitamin D deficiency (<30 ng/mL). Vitamin D administration leads to decrease of fast blood sugar and HbA1c levels significantly in treated group without effect on calcium and alkaline phosphatase levels. So, no significant alterations occurred in calcium and alkaline phosphatase levels after supplementation with vitamin D. CONCLUSIONS: This study showed that HbA1c may be reduced by administration of vitamin D to children and adolescents with T1D without changing the dose of insulin.

High frequency of metabolic syndrome in adult Zoroastrians in Yazd, Iran: a cross-sectional study.

BACKGROUND: Metabolic syndrome (MS) is a cluster of metabolic disturbances, and its prevalence is increasing worldwide. MS exhibits variations among ethnic groups. Zoroastrianism is an ethnic minority which has maintained its isolation and endogamy up to now. So, we evaluated the frequency of MS in Zoroastrians of Yazd, Iran. METHODS: In this cross-sectional study, participants aged ≥30 years were selected using a systematic random sampling. Weight, height, body mass index (BMI), waist circumference (WC), hip circumference (HC), waistto- hip ratio (WHR) and blood pressure (BP) were measured using standard methods. Also, blood levels of glucose, triglycerides (TG), total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), urea, creatinine and uric acid (UA) were measured. Both revised National Cholesterol Education Program Adult Treatment Panel III (ATPIII) and Joint Interim Statement (JIS) criteria were used to diagnose the MS. RESULTS: The mean±SD age of the participants (n=403) was 56.9±12.8 years. The frequency of MS was 69.7% and 74.9% based on JIS and ATPIII criteria, respectively; this was significantly different by age, marital status, job, educational level, and menopausal status (p<0.05). The most prevalent abnormal parameters of MS according to ATPIII and JIS criteria were high WC (95%) and low HDL (87.9%), respectively. Mean LDL, systolic BP, WHR, UA, urea, and creatinine were different between men and women. The difference between the age groups was statistically significant for BMI, systolic BP, diastolic BP, TG, WHR and urea (p<0.05). CONCLUSION: This study showed a high frequency of MS in Zoroastrians of Yazd, Iran.

Increased serum oxidized low-density lipoprotein levels in pregnancies complicated by gestational diabetes mellitus.

BACKGROUND: Elevated serum levels of oxidized Low-density Lipoprotein (oxLDL) have been found in type 2 and in poorly controlled diabetic patients. Gestational diabetes mellitus (GDM) has common features with type 2 diabetes. OBJECTIVE: The aim of our study was to evaluate the serum levels of oxLDL in women with GDM compared to normal pregnant women. MATERIALS AND METHODS: In this cross-sectional study, ninety-two subjects were randomly allocated to either GDM (n=46) or control (n=46) groups matched for age, body mass index and parity from March 2013 to March 2014. GDM was diagnosed according to the American Diabetes Association criteria at 24-26 weeks of gestation. OxLDL was measured using enzyme-linked immunosorbent assay. T-test and Pearson correlation coefficients were applied for analyzing the data by using SPSS version 17. RESULTS: Compared to the controls, significantly higher oxLDL levels were found in the GDM group (17.16 ± 3.71 U/L vs. 8.77 ± 1.84 U/L, respectively, p < 0.001). No significant correlations were found between oxLDL and age and BMI of the patients in the groups. CONCLUSION: Our study found significant increase of oxLDL in GDM emphasizing the role of short-term hyperglycemia in the formation of oxLDL during GDM. The importance of aptly diagnosis of GDM in maternal health may also be concluded.

Effect of exposure to a mixture of organic solvents on hearing thresholds in petrochemical industry workers.

INTRODUCTION: Hearing loss is one of the most common occupational diseases. In most workplaces, workers are exposed to noise and solvents simultaneously, so the potential risk of hearing loss due to solvents may be attributed to noise. In this study we aimed to assess the effect of exposure to mixed aromatic solvents on hearing in the absence of exposure to hazardous noise. MATERIALS AND METHODS: In a cross-sectional study, 99 workers from the petrochemical industry with exposure to a mixture of organic solvents whose noise exposure was lower than 85 dBA were compared with 100 un-exposed controls. After measuring sound pressure level and mean concentration of each solvent in the workplace, pure-tone-audiometry was performed and the two groups were compared in terms of high-frequency and low-frequency hearing loss. T-tests and Chi-square tests were used to compare the two groups. RESULTS: The mean hearing threshold at all frequencies among petrochemical workers was normal (below 25 dB). We did not observe any significant association between solvent exposure and high-frequency or low-frequency hearing loss. CONCLUSION: This study showed that temporary exposure (less than 4 years) to a mixture of organic solvents, without exposure to noise, does not affect workers' hearing threshold in audiometry tests.

The effect of different doses of vitamin D supplementation on insulin resistance during pregnancy.

Low serum vitamin D levels are correlated with insulin resistance during pregnancy. We have assessed the effects of different doses of vitamin D on insulin resistance during pregnancy. A randomized clinical trial was done on 120 women with a gestational age of less than 12 weeks. The women were divided into three groups randomly. Group A received 200 IU vitamin D daily, group B 50,000 IU vitamin D monthly and group C 50,000 IU vitamin D every 2 weeks from 12 weeks of pregnancy until delivery. The serum levels of fasting blood sugar (FBS), insulin, calcium and 25-hydroxyvitamin D were measured before and after intervention. We used the homeostatic model assessment of insulin resistance (HOMA-IR) as a surrogate measure of insulin resistance. The mean ± standard deviation of serum 25-hydroxyvitamin D increased in group C from 7.3 ± 5.9 to 34.1 ± 11.5 ng/ml and in group B it increased from 7.3 ± 5.3 to 27.23 ± 10.7 ng/ml, but the level of vitamin D in group A increased from 8.3 ± 7.8 to 17.7 ± 9.3 ng/ml (p < 0.001). The mean differences of insulin and HOMA-IR before and after intervention in groups A and C were significant (p = 0.01, p = 0.02). This study has shown that supplementation of pregnant women with 50 000 IU vitamin D every 2 weeks improved insulin resistance significantly.

Pulmonary adverse effects of welding fume in automobile assembly welders.

Welding is one of the key components of numerous manufacturing industries, which has potential physical and chemical health hazards. Many components of welding fumes can potentially affect the lung function. This study investigates the effects of welding fumes on lung function and respiratory symptoms among welders of an automobile manufacturing plant in Iran. This historical cohort study assesses 43 male welders and 129 office workers by a questionnaire to record demographic data, smoking habits, work history and respiratory symptoms as well as lung function status by spirometry. The average pulmonary function values of welders were lower relative to controls with dose-effect relationship between work duration and pulmonary function impairment. The prevalence of chronic bronchitis was higher in welders than controls. Our findings suggest that welders are at risk for pulmonary disease.

Pulmonary effects of spot welding in automobile assembly.

BACKGROUND: Spot welding is a type of resistance welding in which pieces of metals are pressed together and an electric current is passed through them. Spot welders are at risk of contact with some potentially hazardous agents but there are few studies about the respiratory effects of spot welding. AIMS: Our objective was to study lung function and respiratory symptoms among spot welders and office workers at an automobile assembly factory in Iran. METHODS: This was a cross-sectional study of 137 male spot welders and 129 office workers. We used a questionnaire to record demographic data, smoking habits, work history and respiratory symptoms. Spirometry was performed to assess lung function status. Metal fume samples from the respiratory zone of spot welders were analysed. RESULTS: The concentrations of metal fume were less than the American Conference of Industrial Hygienists (ACGIH) threshold limit values. There were significantly lower values for average forced expiratory volume in 1st second (FEV(1)), FEV(1)/forced vital capacity and 25-75% forced expiratory flow in spot welders compared to controls. There was also a significantly raised prevalence of respiratory symptoms (sputum and dyspnoea) in spot welders. Fifteen per cent of spot welders and 1% of controls had an obstructive pattern in spirometry. CONCLUSIONS: Our survey suggests that spot welders are at risk of developing respiratory symptoms and decreasing pulmonary function values despite their exposure to components of welding fume being within ACGIH guidelines.

Effect of vitamin C on blood glucose, serum lipids & serum insulin in type 2 diabetes patients.

BACKGROUND & OBJECTIVE: Diabetes mellitus is one of the most common metabolic disorders that causes micro- and macro-vascular complications. Because of additive effects of hyperglycaemia and hyperlipidaemia for cardiovascular diseases, lipid abnormalities should be evaluated in diabetes. As vitamin C is known for its beneficial effects on serum lipids and glycated haemoglobin (HbA1c), we evaluated the effect of different doses of vitamin C on blood glucose, serum lipids and serum insulin in individuals with type 2 diabetes mellitus. METHODS: A total of 84 patients with type 2 diabetes referred to Yazd Diabetes Research Center, Iran, were included in the study. They received randomly either 500 mg or 1000 mg daily of vitamin C for six weeks. Fasting blood sugar (FBS), triglyceride (TG), total cholesterol (TC), low and high density lipoprotein (LDL, HDL), glycated haemoglobin HbA(Ic) and serum insulin were measured before and after vitamin C consumption and the results were analyzed. RESULTS: A significant decrease in FBS, TG, LDL, HbA1c and serum insulin was seen in the group supplemented with 1000 mg vitamin C. The dose of 500 mg vitamin C, however, did not produce any significant change in any of the parameters studied. INTERPRETATION & CONCLUSION: Our results indicate that daily consumption of 1000 mg supplementary vitamin C may be beneficial in decreasing blood glucose and lipids in patients with type 2 diabetes and thus reducing the risk of complications.