Iranian Journal of

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Background and Objectives: Noise-induced hearing loss is a prevalent work-related morbidity in the country. We determined the strength of association between hearing loss and occupational noise exposure as the first step in prevention programs.
Material and Methods: A historical cohort study involving 100 exposed and 31 non-exposed subjects was conducted. Noise exposure was estimated using sound level meter BSEN 60651, Type 2. Past noise exposure was estimated using the existing data on the place and type of work. Audiometry was used to assess hearing loss in each subject in 3- year intervals on an occupational cohort from 1993-2004.

Results: Noise-induced hearing loss was found in 49% (49 subjects) of the exposed group and 9.7 %( 3 subjects) of non-exposed group (p<.0001). Nobody used any form of hearing protection routinely in either group. Relative risk for noise-induced hearing loss was 5.1(CI95%: 1.7- 15.1).Time at risk was estimated 24.9 years (22.7-27.1) in exposed and 22.2 years (20.7-23.7) in unexposed group by survival analysis.
Conclusion: More legislation, hearing conservation programs, and surveillance and biological monitoring of work sites and workers are required to prevent occupational hearing loss. Planning strategies for noise assessment and control can help improve the work environment. Gross occupational exposure to noise has been demonstrated to cause hearing loss and the authors believe that occupational hearing loss in the country is a widespread problem.

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Background and Objectives: Brucellosis in livestock has led to a significant reduction in the economic capital in Iran. Estimation of the economic losses due to this disease helps to highlight the importance of the disease and makes it easy to justify brucellosis control programs.

Methods: Estimation was done based on the data received from the Iran Veterinary Organization and statistics book of the Iranian Ministry of Agriculture. Economic Loss was estimated assuming the equality of the incidence of the disease in total livestock population with its incidence in tested livestock. The direct costs of culled brucella positive animals, reduced milk production, reduced weight of animal, abortion, and reduced fertility were calculated based on the price of the animal or the product in each year. Due to inflation, the costs were adjusted using the discount rate. Therefore, the losses were compared in each year.

Results: The maximum loss due to brucellosis in the studied period occurred in 2014. Comparison of the losses due to bovine and ovine brucellosis showed that the total economic loss in the sheep and goat population was 5.53 times greater than the loss in the cattle population. Estimation of total economic loss in 12 years of the study was 8,129,116 million IRR (1 USD≅35000 IRR).

Conclusion: More serious attention should be paid to animal brucellosis from both health and economic points of view. Prevention from massive economic losses and human brucellosis control and eradication will not be possible without controlling the disease in the animal population.

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Background and Objectives: Periodontal disease is one of the most common oral health problems. Clinical attachment loss occurs in sever periodontal cases (CAL>3). In this study, we applied a classic regression model and the models that consider the hierarchical structure of the data to estimate and compare the effect of different factors on CAL.
 
Methods: This cross-sectional study was performed in 375 pregnant women and 192 mothers of three-year-old children. The data were gathered from 16 health networks of Shahid Beheshti University of Medical Sciences, Tehran, Iran. CAL was determined for 6 teeth per person by a dentist according to WHO standard oral health examination form. Three-level and ordinary logistic regression analyses were applied for data analysis using the STATA software 14.
 
Results: Of 3,402 examined teeth, 6.3% had CAL> 3mm. Based on the obtained results, the odds of CAL>3mm were 2.4 in the third semester compared to non-pregnant women. The odds of CAL>3mm were 2.86 in women without daily floss use compared to women with routine daily floss use. Posterior teeth were more likely to have CAL>3m than anterior teeth (OR = 1.65) (P-value < 0.05).
 
Conclusion: According to the AIC index, multi-level logistic regression model has a better fit than ordinary logistic regression model and can estimate the coefficients of factors related to CAL>3mm more precisely. The use of the ordinary logistic regression model in hierarchical data can result in underestimated standard errors of the estimated parameters.

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