***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract Objective : A revised hearing conservation program ( HCP ) was implemented in the Swedish Armed Forces in 2002 . The aim of this study was to evaluate the incidence of significant threshold shifts ( STS ) in male conscripts heavily exposed to noise after the implementation of the new HCP  , comparing the results to those of an earlier study from 1999/2000 . Design : The study was prospect i ve and longitudinal , covering the period from reporting to military service to discharge . The outcome measure was the incidence of STS . Statistics from the military insurance system was analysed . Study Sample : A total of 395 conscripts were included in the study ( mean age 19 years ) . The control group ( n : 839 ) consisted of men of the same age . Results : In 2004/2005 the incidence rate of STS was 2.3 % compared to 7.9 % in 1999/2000 and compared to 3.7 % among the controls . The number of cases of auditory complications reported from conscripts to the insurance system has decreased , from 16 to 5/100 000 days of military training , during the last decade . Conclusions : The new HCP apparently reduced the incidence rate of STS to one third compared to before the program was introduced and leveled it to the incidence rate in the control-group not exposed to military noise OBJECTIVES ( 1 ) To conduct a contemporary analysis of historical data on short-term efficacy of a 3-year hearing conservation program conducted from 1992 to 1996 in Wisconsin , USA , with 753 high school students actively involved in farm work ; ( 2 ) to establish procedures for assessment of hearing loss for use in a recently funded follow-up of this same hearing conservation program cohort . METHODS We analyzed a pragmatic cluster-r and omized controlled trial , with schools as the unit of r and omization . Thirty-four rural schools were recruited and r and omized to intervention or control . The intervention included classroom instruction , distribution of hearing protection devices , direct mailings , noise level assessment s , and yearly audiometric testing . The control group received the audiometric testing . RESULTS Students exposed to the hearing conservation program reported more frequent use of hearing protection devices , but there was no evidence of reduced levels of noise-induced hearing loss ( NIHL ) . CONCLUSION Our analysis suggests that , since NIHL is cumulative , a 3-year study was likely not long enough to evaluate the efficacy of this intervention . While improvements in reported use of hearing protection devices were noted , the lasting impact of these behaviors is unknown and the finding merits corroboration by longer term objective hearing tests . A follow-up study of the cohort has recently been started BACKGROUND Noise-induced hearing loss ( NIHL ) is one of the most common occupational diseases and the second most common cause of workers ' cl aims for occupational injuries . OBJECTIVE Due to high prevalence of NIHL and several reports of improper use of hearing protective devices ( HPDs ) , we conducted this study to compare the effect of face-to-face training in effective use of earplugs with appropriate NRR to overprotection of workers by using earplugs with higher than necessary noise reduction rating ( NRR ) . METHODS In a r and omized clinical trial , 150 workers referred to occupational medicine clinic were r and omly allocated to three arms --- a group wearing earplugs with an NRR of 25 with no training in appropriate use of the device ; a group wearing earplugs with an NRR of 25 with training ; another group wearing earplugs with an NRR of 30 , with no training .  Hearing threshold was measured in the study groups by real ear attenuation at threshold ( REAT ) method . This trial is registered with Australian New Zeal and clinical trials Registry , number ACTRN00363175 . RESULTS The mean ± SD age of the participants was 28 ± 5 ( range : 19 - 39 ) years . 42 % of participants were female .  The mean noise attenuation in the group with training was 13.88 dB , significantly higher than those observed in other groups . The highest attenuation was observed in high frequencies ( 4 , 6 , and 8 kHz ) in the group with training . CONCLUSION Training in appropriate use of earplugs significantly affects the efficacy of earplugs --- even more than using an earplug with higher NRR OBJECTIVES The study was done to determine whether the noise attenuation attained with the use of earplugs can be improved by teaching the proper insertion of earplugs to users . METHODS Fifty-four r and omly selected male subjects were divided into an untrained group ( 25 persons ) and a trained group ( 29 persons ) . The trained group was given a lecture on earplug insertion and allowed to practise the insertion procedure , whereas the untrained group acted as controls . The untrained group received this training afterwards . The success of the training was measured by the  MIRE ( microphone in real ear )  and REAT ( real ear at threshold ) methods , visual evaluation and an analysis of the properties of the subjects ' ear canals . RESULTS According to the MIRE method , the averaged A-weighted noise attenuation was 21 dB for the untrained group and 31 dB for the trained group . With the REAT method the attenuation at 1000 Hz was 24 dB for the untrained group and 30 dB for the trained group . The visual evaluation of the earplug fit was 1.9 for the untrained group and 2.6 for the trained group ( scales 0 - 3 ) . CONCLUSION The results indicate that training in earplug insertion is important for good attenuation and for diminishing poor attenuation to a minimum Objective Occupationally acquired noise-induced hearing loss ( NIHL ) is the most prevalent occupational disease in Austria and among the most common in many other countries . Because of the wide variation in hearing loss after equivalent exposures it has long been assumed that some individuals are more vulnerable to occupational NIHL than others . Earlier attempts to define predictors of NIHL before starting occupational noise exposure have largely failed . We present results of a prospect i ve study evaluating the potential of temporary threshold shift ( TTS ) after a test exposure to predict NIHL . Methods Between 1982 and 1989 , overall 311 apprentices were included into a prospect i ve study during their initial health screening visit . At this occasion , a st and ardised noise exposure was applied ( 20 min , 200–500 Hz , 100 dBA ) and the TTS at 4 kHz was determined during at least 10 min after exposure . Hearing loss was monitored at follow-up visits every 3–5 years . Follow-up was 13 years on average . Results Permanent threshold shift was predicted by duration of noise exposure , frequency of wearing noise protectors and especially by the initial TTS at 4 kHz . Using 14 dB TTS as a cut-off had 82 % sensitivity and 53 % specificity to predict 20 dB or higher levels of NIHL . Conclusions The TTS model can be successfully applied as a method to detect individuals at greater risk of occupational NIHL . It is recommended to routinely include such a procedure into initial workers ’ examinations for suitability to work under occupational noise conditions and for counselling on the use of hearing protectors OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity OBJECTIVES To review the evidence suggesting that  occupational hearing conservation programs  prevent noise-induced hearing loss ; to describe the features , prevalence , and h and icap associated with noise-induced hearing loss ; and to describe the otolaryngologist 's role in prevention of noise-induced hearing loss . DATA SOURCES Recent statements from the American College of Occupational Medicine , the National Institutes of Health , and the International Organization for St and ardization are supplemented by published articles known to the author ( no formal literature search was done ) . STUDY SELECTION Articles that purported to measure the effects of occupational hearing conservation programs on preventing noise-induced hearing loss . DATA EXTRACTION Each article was separately critiqued without a priori assessment criteria . DATA SYNTHESIS Several studies suggest that occupational hearing conservation programs prevent noise-induced hearing loss , but none of these are conclusive . No r and omized clinical trial has been reported , of which I am aware , and previously reported data suffer from one or more of the following shortcomings : failure to match treatment and control groups for age , nonoccupational noise exposure , and /or prior hearing loss ; failure to control for audiometric learning effects ; and inclusion of workers who had already worked long careers without hearing protection ( and thus had little risk of additional noise-induced loss ) . CONCLUSION Although noise reduction for individuals obviously can prevent noise-induced hearing loss , to my knowledge , no single study offers convincing evidence of the efficacy of occupational hearing conservation programs , primarily due to method ologic flaws The aim of the study was to investigate the incidence and the relative risk of significant threshold shift ( STS , ≥15 dB deterioration at any ear and audiometric frequency ) during primary military service ( 7–9 months ) , and to investigate whether subjects with an initial slight hearing loss ( thresholds ≥ 25 dB HL at any audiometric frequency and ear ) were under increased risk . The investigation was made as a prospect i ve audiometric study and included 747 men . An age-matched group of 138 individuals served as an unexposed control group , whose incidence of STS was 2.9 % . In the exposed group the incidence was 7.9 % and the relative risk 2.7 risk ratio ( RR ) . In the subgroup of 95 persons , who already at reporting-for-training had a mild hearing loss , the incidence was 17 % . The relative risk for STS in this group compared to the control group was 6.8 ( RR ) , and compared to those with normal hearing at reporting was 3.1 ( RR ) . In spite of hearing conservation efforts , hearing deterioration still occurs , above all in the artillery . Those who already at reporting-for-training had a mild hearing loss were at higher risk for STS compared to those with initially normal hearing Although r and omised trials are widely accepted as the ideal way of obtaining unbiased estimates of treatment effects , some treatments have dramatic effects that are highly unlikely to reflect inadequately controlled biases . We compiled a list of historical examples of such effects and identified the features of convincing inferences about treatment effects from sources other than r and omised trials . A unifying principle is the size of the treatment effect ( signal ) relative to the expected prognosis ( noise ) of the condition . A treatment effect is inferred most confidently when the signal to noise ratio is large and its timing is rapid compared with the natural course of the condition . For the examples we considered in detail the rate ratio often exceeds 10 and thus is highly unlikely to reflect bias or factors other than a treatment effect . This model may help to reduce controversy about evidence for treatments whose effects are so dramatic that r and omised trials are unnecessary . The relation between a treatment and its effect is sometimes so dramatic that bias can be ruled out as an explanation . Paul Glasziou and colleagues suggest how to determine when observations speak for 
    Output:
    
Earmuffs might perform better than earplugs in high noise levels but worse in low noise levels ( very low- quality evidence ) .
Better use of HPDs might reduce hearing loss but other components not ( very low- quality evidence ) .
Hearing loss prevention and interventions modestly reduce noise exposure and hearing loss .