7578409643

o

dB

Frequency (Hz)

l— SO* (high)    SD* (Iow)

Fig. 2. Mean hearing levels in the ieft car for workers in the noisy plant (exf>osed workers).

TABLE 2

Companson of Puretone and Speech Oiscnmination Test Scores »> Men by Age and Degree of Noise induced Hearing Loss*

Severe Noise -Induced* Hearing Loss (n = 74)

Nonsevere Noise-łnduced Mcaring Loss (n = 58)

	Me»n	(SO)	Mean	(SO)
Age 56-63 y Average speech reception	19.1	(10.1)	17.2	(15.6)
threshold Average speech discrimination	42.2	(19.6)	62.0	(20.5)t
score (tn noise) Average hearing thresholds 3000 dB	60.7	(12.2)	39.1	(19.9)
4000 dB	68.0	(119)	49.1	(18.1)
6000 dB	66.4	(16.6)	48.4	(19.5)
Age 64-68 y Average speech reception	23.2	(12.9)	16.1	(98)
threshold Average speech discrimination	41.3	(20.4)	60.8	(21.6)%
score (in noise) Average hearing thresholds 3000 dB	63.0	(12.2)	37.7	098)
4000 dB	69.6	(12.5)	48.2	(17.3)
6000 dB	70.7	(15.7)	44.8	(18.2)

* *65 dB loss at 3. 4. or 6 kHz. t fiest. t = 5.6. dt - 130. P <.0001. X t test. f » 4.6. df ^m 111.P< .001.

gories in both age groups. The monosyllabic discrimi-nation tests administered in quiet areas yieid scores very close to 100% in normal listeners. However, when the same test materials are administered with a com-peting noise of 6 simultaneous speakers at a signal-to-noise ratio of O dBA, normal listeners score was between 80% and 90%. Speech reception threshold and speech

discrimination scores did not differ according to noise-induccd hearing loss in the 56 to 63-year-old group.¹³ Araong the older group, a difference was noted in the speech discrimination score between noise-induced hearing loss workers compared with the nonnoise-induccd hearing loss workers (83.2% (SD 11.5] v 91.1% (SD 7.1]. P< .01).

W-22 MAX represents the maximum speech discrimination score for the better ear when words are pre-sented in combination with competing noise. It was usually morę difficult to proccss speech in noise than in quiet conditions. In the noise prosentation conditions, subjects with a lesser degree of noise-induced hearing loss scored almost 20 pcrcentage points higher in dis-criminating word lists in noise than their age countcr-parts (P < .001). In the case of the two older age groups, subjects with less noise-induced hearing loss scored 7.7 perccntage points higher in quiet (t = 3.9, df — 111, P< .001) and 19.5 percentagc points higher in noise conditions relative to subjects with morc noise-induced hearing loss (f = 4.6, df — 111, P< .001). Thus, differcnces in degree of higher frcąuency hearing loss appear related to abitity to discriminate speech stimuli, particularly in the presence of competing noise.

Hypertension and lis Risk Factors According to Hearing Levels

The mean ages of the younger group with and without noise-induced loss were similar (60.5 and 60.8, respec-tively) (Table 3). Body mass index was higher in the nonsevere noise loss group (P < .05). Their average years of employment were 30.2 and 30.1, respectively. For older men with or without severe noise-induced hearing loss, the mean age was 65.9 and 65.4 years, respectively. Body mass index was similar (28.1 v27.1), as was average length of employment (29.0 years) (Table 2).

A greater proportion of severc noise-induced hearing loss workers aged 64 to 68 years were currently taking blood pressure medications (39.2% v 20.5%, P < .05). The mean unadjusted blood pressures for these two groups were 144.1 mm Hg and 141.9 mm Hg systolic, respectively, and mean diastołic 84.0 mm Hg and 82.2 mm Hg, respectivety (P value not significant).

There were no significant differenccs between the mean systolic or diastołic blood pressure for either age group dichotomized by hearing lass category (Table 3). Amoag men 64 to 68 years of age, there was a trend toward inereased prevalence of high blood pressure in those with severe noise-induced hearing loss compared with those not meeting this criteria (39 of 77 (50.6%] v 11 of 36 (30.5%]. P = .07). No evidence of a relationship was scen among men aged 56 to 63 years.

The overall distribution of speech discrimination scores by hypertension status is shown in Fig. 3. There is a relationship between poor speech discrimination scores in noise (<60%) and HBP (P< .05). Similar to the noise-induced hearing loss category, when these variables were further c&tegorized by age, older hyper-tensive men were twice as likely to exhibit poorer speech

693

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