Int Arch Occup Environ Health ( 1990) 62:259-260 International Archives of

O Cet UpationalndEnvmronmentalHealth© Springer-Verlag 1990

Short communication

Noise-induced hearing loss and blood pressure

Sanja Milkovi 6-KrausInstitute for Medical Research and Occupational Health, M Pijade 158, POB 291, Y-41001, Zagreb, Yugoslavia

Received March 14, 1989 / Accepted January 10, 1990

Summary The study was carried out on 85 workers withlong-term exposure to noise levels exceeding 85 d B (A).The control group consisted of 85 workers who hadnever been exposed to noise levels greater than recom-mended, i e 85 d B(A), in their working environment.All the workers in the exposed group had hearing losswhich was confirmed by audiometry The Mann-Whit-ney test was used for statistical assessment The systolicas well as the diastolic blood pressure in the exposedgroup was increased (P < 0 001), respectively (P < 0 01).

Key words: Noise Blood pressure Non-auditory ef-fect

otological examination, including otoscopic examination and au-diometry, and written confirmation from the general practitionerthat workers had had no medical history of cranial trauma, menin-goencephalitis or treatment with ototoxic drugs in order to excludeother possible ear pathology All workers included in the studycame to our outpatient clinic complaining of hearing loss and be-cause of possible compensation claims Each worker had the exactnoise level measurement in his working environment, and onlythose with 85 d B(A) or more were included in the study Au-diometry was performed in a sound isolated cabin after a period of24 h, during which the workers had not been exposed to noise Thecriteria for noise-exposed hearing loss was a decrease in hearing of40 d B (A) or more Systolic and diastolic blood pressure readingswere taken from the left arm with mercury sphygmomanometerwhile the subject was seated Measurements were expressed in mmof mercury and recorded to the nearest even number The bloodpressure was measured only in the morning to avoid its diurnalrhythm ( 10:00 12:00 h).

Introduction

The most frequent occupational disease is probably hear-ing loss caused by exposure to noise in industry It is arare cause of absence from work as an isolated finding,although this may be because relatively much less atten-tion is paid to the non-specific, non-auditory effects ofnoise One of the possible non-auditory effects of noiseis increased blood pressure Some authors have suggest-ed that prolonged exposure to noise has no effect onblood pressure lCartwright and Thompson 1975 ; Sandenand Axelsson 1981 ; Belli et al 1984 l, while other au-thors in their investigations have found that noise expo-sure did increase blood pressure lAndren et al 1980,1983 ; Andren 1982 ; Wu et al 1987 l.

Material and methods

A total of 85 male workers with exposure to noise levels exceeding85 d B(A) from three factories were examined, and the samenumber of male workers who had never been exposed to noiselevels exceeding 85 d B(A) This investigation included, for ex-posed workers, confirmation from work organizations of the dura-tion of exposure to noise levels measured at the working place,

Results

Hearing loss in all 85 male workers exposed to noise wasconfirmed by audiometry None of the workers had a

p < O 001 p < O 01

Fig 1 Sample average and standard error estimate (S ) Systolic

blood pressure Exposed to noise > 85 d B(A); :l control Di-astolic blood pressure E Exposed to noise; :ll control

1

1

1

260

positive medical history or possible other ethology thatcould have caused the hearing loss Each worker in thegroup exposed to noise had a pair-matched control ac-cording to age, education, work strain and work condi-tions Correction for relative weight was not calculated.When two groups of workers were compared by theMann-Whitney test for pair-matched analysis, the sys-tolic as well as diastolic blood pressure in the exposedgroup was increased (P < O 001) respectively (P < 0 01).

Discussion

In this study there is a marked relation between expo-sure to noise and blood pressure (Fig 1) Therefore, itcan be concluded that there is a non-auditory effect ofnoise on both systolic and diastolic blood pressure Thisdoes not agree with van Dijk et al ( 1987) and Wu et al.( 1987), but it does agree with the findings of Jonsson andHansson ( 1977) and Talbott et al ( 1985) It is still notclear why different authors have such inconsistent find-ings on this topic and in this study the intention was toexclude other possible effects that could influence bloodpressure, such as age, work strain and work conditions.This was considered essential because, as Dresen andBorghols ( 1978) observed, dynamic physical load in-hibits the effect of noise exposure on diastolic bloodpressure, and Hensch et al ( 1981) observed that physi-cal load in combination with mental load may enhancediastolic blood pressure It is not yet possible to drawconclusions on whether hypertension develops after thehearing loss or concomitantly However, if we turn tothe research of other authors on human volunteers, whofound in their subjects that diastolic pressure increasesduring exposure to noise (von Eiff et al 1981 ; Andren etal 1980, 1981 ; Ising and Giinther 1983), it could be pre-sumed that noise is a contributory factor in the develop-ment of elevated arterial pressure The controversy inresults indicates the necessity of more investigations inthis field of occupational health.

Conclusion

This study provides more evidence that the noise ex-posure of workers exposed to noise levels exceeding85 d B(A), and which has already caused hearing loss,leads to increased blood pressure However, it must be

acknowledged that some other causes in environmentalworking conditions may also have an influence on bloodpressure as suggested by van Dijk ( 1986).

Acknowledgements I thank Dr V Jovanovi C, Ph D , who kindlyhelped in statistical evaluation of the data.

References

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