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population to characterizc moro fincly their audiological profile and to assess further tho relationship of noisc-induccd hearing loss as a marker for incrcascd cisk of hypertension.

The plant that employed thesc men was dividcd into six major scctions: Press Room. Tool and Die, Metal Asscmbly, Blank and Sheer, Steel Storage, and Smali Press. Thesc aro not partitioncd by wałls of any kind.

The workers in the plant arc engaged in tlić fabrica-tion and partial asscmbly of large metal parts. A sound survcy was conducted using both a Gen Rod 1565A sound lcvel meter as woli os a Metro Loggor dB-301 dosimeter. The averagc noise lcvcl within the plant was 89 dBA. The noise has becn deseribed as continuous and severe in all are&s of the plant. A normal conversation is considered impossiblc.

Since 1978 there has becn a mandatory hearing con-servation program in effect. Whon men who participated in the study werc quoricd concerning their current usc of hearing protcction, 39% reported w ca ring protcction always or almost always. Howcvcr, before 1978, vcry fow of the men uscd hearing protection of any kind.

Study Oesign

There were 616 men who were members of the union retirement organization as of April 1, 1984. The study population consisted of men aged 56 to 68 with 20+ years of employment at the plant and !iving within a 50-mile radius. A total of 137 workers were ineligible because they had moved out of the statc or liwed beyond the 50-mile radius of our study area. Of the 479 remain-ing. 110 were ineligible because they were over or under age or currcntly working. Sixty-eight was chosen as the cutofT because the smali numbers available at older ages may unduly confound the effects of noise expo$ure. Fiftecn people from the origin&l sample were deceased, 67 refused and 245 were screened. An additional 42 . were unable to be contacted. The ovcrall response ratę was 78.6%. Clinical examination ineluded mcasures of height, weight, pulse. and blood pressure, as well as a detailed medical and pcrsonal habit history, alcohol consumption, and smoking patterns. There was also a detailed questionnaire on occupational and military history and noisy hobbies. The examination and interview were administered at the union hall. An audiometrie cvaluation was also conducted. This consisted of air and bonę conduction, audiometry, speech rcception thresh-old, word discrimination testing, and an index of social interaction and communication.

Multiple blood pressure measurements using standard procedures were implemented in this investiga-tion.^M Blood pressure was determined by a nurse three times within 5 minutes after a lO-minute rest and then repcated by a second nurse 15 rainutes la tor.

The following st&nd&rdized procedures were utilized. All blood pressure measurements were taken using the participanfs right arm in a sitting positton. A standard mercury sphygmomanometer and random zero device were used for all measurements. Tho first measurements

of cach set of three were taken with tho standard dcvic« foltowcd by two rcadingS of the zero muddlor. The systolic and diastolic blood pressures of cach worker wcrc determined by the overall mean of four zero mud-dler measurements at one timo.

The first and fifth Korotkoff sounds wcrc rccordcd as the systolic and diastolic blood pressure, rcspectivcly. In addition, a history of cardiovascular discasc and history of treatment for high blood pressure wcrc ob-tained. The usc of antihypcrtcnsivc therapy was also ascertaincd including both currcnt and prcvious use.

Standardized audiometrie testing procedures were uscd. The testing was conducted by a certiflcd audiolo-gist. The procedurc uscd for conducting the pure-tone audiogram includes the basie features of the Hughson Westlakc technique for determining the pure-tone hearing thrcshold.¹⁵ All audiometrie testing was performed in testing booths that conform to the American National Standards criteria for background noise in audiometrie rooms.¹⁴ All thresholds wcrc measured with a single TDH headphonc. The audiometers wcrc initially cali-brated and periodicałly checkcd thereafter. The sound pressure output of the audiometer was calibratcd monthly. A noise exposure questionnairc, which outlincd information on employment. hobbies. military service, hearing disorders. was administered to cach worker.

The rcvised Hearing Performance Inventory (HPI) developed by Lamb et al²¹ to assess the communicativc difficulty of hearing-impaired persons in a variety of everyday listening situations was administered to this population.

The Interpersonal Support Evaluation has been employed in a total of 12 studies as a measure of support functions. For psychometrie properties. correlation, and scalę validity refer to Cohen et aL“ Responses to 36 items on the Interpersonal Support Evalu&tion and six questions designed to measure anxiety were administered. Responses to the 40 questions were categorized into six choiccs: I agree very much. I agree pretty much, 1 agree a little, I disagree a little, I disagree pretty much, and I disagree very much.

Resulls

Cohort Description

The age distribution of the total group is shown in Table 1. The mean age was 63 years (SD = 3.2). The present study utilized two age strata consisting of 56 to 63 years and 64 to 68 years. Diastolic blood pressure did not vary markedly with age. However, there was an age-related systolic blood pressure inereose (P < .01). The avcrage number of years of work at this plant was 29.9 (SD = 4.2). No consistent pattern in blood pressure by total years of employment was aoted. The initial dato of hire ranged from 1946 to 1970 with 90% of the mean reporting a 1950 to 1953 entry into tho plant. The &verage datę of retirement was 1981 (SD = 4.0). There-fore, this cohort had been removcd from daily exposure to noise for approximately 4 years.

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Journal of Occupational Medicine/Volume 32 No. 8/August 1990