Application of the kurtosis statistic to the evaluation of the risk of hearing loss in workers exposed to high-level complex noise.

OBJECTIVE: Develop dose-response relations for two groups of industrial workers exposed to Gaussian or non-Gaussian (complex) types of continuous noises and to investigate what role, if any, the kurtosis statistic can play in the evaluation of industrial noise-induced hearing loss (NIHL). DESIGN: Audiometric and noise exposure data were acquired on a population (N = 195) of screened workers from a textile manufacturing plant and a metal fabrication facility located in Henan province of China. Thirty-two of the subjects were exposed to non-Gaussian (non-G) noise and 163 were exposed to a Gaussian (G) continuous noise. Each subject was given a general physical and an otologic examination. Hearing threshold levels (0.5-8.0 kHz) were age adjusted (ISI-1999) and the prevalence of NIHL at 3, 4, or 6 kHz was determined. The kurtosis metric, which is sensitive to the peak and temporal characteristics of a noise, was introduced into the calculation of the cumulative noise exposure metric. Using the prevalence of hearing loss and the cumulative noise exposure metric, a dose-response relation for the G and non-G noise-exposed groups was constructed. RESULTS: An analysis of the noise environments in the two plants showed that the noise exposures in the textile plant were of a Gaussian type with an Leq(A)8hr that varied from 96 to 105 dB whereas the exposures in the metal fabrication facility with an Leq(A)8hr = 95 dB were of a non-G type containing high levels (up to 125 dB peak SPL) of impact noise. The kurtosis statistic was used to quantify the deviation of the non-G noise environment from the Gaussian. The dose-response relation for the non-G noise-exposed subjects showed a higher prevalence of hearing loss for a comparable cumulative noise exposure than did the G noise-exposed subjects. By introducing the kurtosis variable into the temporal component of the cumulative noise exposure calculation, the two dose-response curves could be made to overlap, essentially yielding an equivalent noise-induced effect for the two study groups. CONCLUSIONS: For the same exposure level, the prevalence of NIHL is greater in workers exposed to non-G noise environments than for workers exposed to G noise. The kurtosis metric may be a reasonable candidate for use in modifying exposure level calculations that are used to estimate the risk of NIHL from any type of noise exposure environment. However, studies involving a large number of workers with well-documented exposures are needed before a relation between a metric such as the kurtosis and the risk of hearing loss can be refined.

[Adaptive designs for clinical trial].

OBJECTIVE: In order to provide readers with general concepts and methodology on adaptive designs for clinical trial. METHODS: Definition of adaptive designs for clinical trial and basic idea of adaptive adjustment were introduced through an example. RESULTS: The relationship between adaptive designs and group sequential design was summarized. Ways to embody two basic statistical rules of clinical trial under adaptive adjustments setting were also introduced. CONCLUSION: Adaptive designs provided clinical trial with a great flexibility, which could greatly improve the efficiency of clinical trial.

Comparison of clinic and ambulatory blood pressure in response to antihypertensive drugs in Chinese patients.

OBJECTIVE: To compare the difference between 24-h ambulatory blood pressure (ABP) and trough clinic blood pressure (CBP) after 8 weeks of therapy. METHODS: The study used meta-regression analysis to summarize three randomized, double-blind, active controlled trials in order to compare the difference between the magnitude of the reduction in 24-h average ABP and CBP Patients. Chinese patients with seated diastolic blood pressure (SDBP) 95-115 mmHg and ambulatory diastolic blood pressure (ADBP) > or =85 mmHg. RESULTS: The average age of 126 patients was 47.7 +/- 8.3 years, ranging from 25 to 67 (95 males and 31 females). All regimens reduced 24-h ABP and CBP after 8 weeks of treatment. In the 126 patients the baseline 24-h SBP and DBP values (142.7/94.4 mmHg) were markedly lower than those for clinic values (152.6/102.6 mmHg; P<0.0001). Similarly, the 24-h SBP and DBP values (132.7/87.7 mmHg) in week 8 were markedly lower than the clinic values (138.9/92.7 mmHg; P<0.0001). The differences between the treatment-induced reductions in 24-h ABP and CBP were statistically significant (the difference was 3.7/3.3 mmHg for SBP/DBP, P=0.0069/P<0.0001). CONCLUSION: All regimens significantly reduced seated CBP and ABP. The effect of antihypertensive treatment was greater on CBP than that on ABP, suggesting that assessment on effectiveness of an antihypertensive treatment using CBP readings only has to be carefully interpreted, and a more systematic application of ABP monitoring should be adopted.

[Efficacy of monotherapy with 15 antihypertensive agents in treating essential hypertension assessed by 24-hour ambulatory blood pressure monitoring].

OBJECTIVE: To evaluate the efficacy of the monotherapy of 15 agents in treating essential hypertension. METHODS: After 2-week wash-out, a total of 370 patients with seated diastolic blood pressure 95-114 mmHg and seated systolic blood pressure < 180 mmHg were randomized to different therapeutic groups. 24-hour ambulatory blood pressure monitoring was performed before medication and at the end of 8 weeks. RESULT: All the agents significantly reduced the 24 hour mean blood pressures after treatment except doxazosin, terazosin, and torasemide. CONCLUSION: The result suggested that the angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, beta-blockers and long-acting calcium antagonists were effective in treating essential hypertension, while the low-dose doxazosin, terazosin and torasemide can be used for combination therapy but not for monotherapy.

[Relationship between sample size and variation of means for personal noise exposure in weaving workers].

OBJECTIVE: To explore the relationship between sample size and variance of means for personal noise exposure in weaving workers as to contributing evidence for establishing personal noise exposure measurement guideline. METHODS: A personal noise exposure measurement database from a group of weaving workers was used in the randomized re-sampling data analysis. The sampling cases were one number selecting from one to fifteen at each randomized re-sampling procedure. The randomized re-sampling was one thousand times from original personal noise exposure measurement database to get one thousands of re-sampling database. One thousands of L(Aeq.8 h) mean were calculated by re-sampling databases. The variation of randomized re-sampling means was analyzed for different re-sampling numbers. RESULTS: The change for narrow trend of maximum, minimum, 95 percent number, 5 percent number of L(Aeq.8 h) mean was faster when randomized re-sampling number was smaller in variation vs randomized re-sampling number curve analysis. After that, the change for narrow trend of L(Aeq.8 h) mean was smooth for increasing the randomized re-sampling numbers. The 95% - 5% of L(Aeq.8 h) mean was about half for randomized re-sampling four cases (3.30 dB) vs one case (7.40 dB), and about one third for seven cases (2.44 dB), and about one fourth for eleven cases (1.85 dB). CONCLUSION: The sample size in personal noise exposure measurement guideline could be selected from four to eleven.

[Adjustment of dose-response relationship of industrial impulse noise induced high frequency hearing loss with different exchange rate].

OBJECTIVE: To explore a new method to evaluate the dose-response relationship between the noise exposure and prevalence of noise induced high frequency hearing loss. METHODS: Physical examination and questionnaire survey were conducted among 32 mechanical workers, 12 males and 20 females, aged 35.1 +/- 7.2, exposed to industrial impulse noise (impulse noise group), and 163 textile workers, 82 males and 81 females, aged 31.5 +/- 8.7, exposed continuous noise (continuous noise group). SH-126 dosimeter was used to measure the A weighted equal sound level in continuous eight working hours (L(Aeq.8h)) so as to evaluate the individual noise exposure. Cumulative noise exposure (CNE) was calculated with the values of L(Aeq.8h) and noise working year adjusted by different exchange rates (ERs) for each worker. Hearing threshold was measured by audiometer with routine method and adjusted by age and gender according to GBZ49-2002. High frequency hearing loss was diagnosed based on the GBZ49-2002 for each worker. RESULTS: According to the equal energy rule, with the ER = 3 the CNE of the impulse noise group was [103.2 dB (A).year +/- 4.2dB (A).year], significantly lower than that of the continuous noise group [110.6 +/- 6.0 dB (A).year, P < 0.05]. With the ER = 5.5, the CNE of the impulse noise group was 110.3 +/- 6.6 dB (A).year, not significantly different from that of the continuous noise group [110.6 +/- 6.0 dB (A).year]. The high frequency hearing loss prevalence of the impulse noise group was 68.8%, not significantly different that of the continuous noise group (65%, P > 0.05). Trend chi square test showed significant differences in the relationship between CNE and hearing loss prevalence among the impulse noise group with the ER = 3, the impulse noise group with the ER = 5.5, and continuous noise group (all P < 0.01). With the ER = 3, the high frequency hearing loss prevalence of the impulse noise group with the CNE of 100-104 dB (A).year was 76.9%, significant higher than that of the continuous noise group (30.4%, P < 0.05); and the high frequency hearing loss prevalence of the impulse noise group with the CNE of 105-108 dB (A).year was 90.9%, significantly higher than that of the continuous noise group (50.0%, P < 0.05). With the ER = 5.5, there was no difference in the prevalence of high frequency hearing loss between the continuous noise group and impulse noise group. Logistic regression model showed that with the ER = 3, the dose-response curve of the impulse noise group presented a left shift and with a slope sharper than that of the continuous noise group. With the ER increasing the dose-response curve of the impulse noise group showed a right shift and with a gradually lowering slope. When the ER equaled to 6 in the impulse noise group and equaled to 3 in the continuous noise group, the two dose-response curves were almost superposed. CONCLUSION: Impulse noise causes more serious damage in causing high frequency hearing loss than continuous noise according to equal energy rule. Increasing the ER value in the impulse noise group adjusts the dose-response curve to be close to that of the continuous noise group.

[Relationship between impulse noise and continuous noise inducing hearing loss by dosimeter measurement in working populations].

OBJECTIVE: To compare the dose-response relationship differences between impulse noise exposure workers and continuous noise exposure workers in prevalence of noise inducing hearing loss using dosimeter measurement. METHODS: Thirty-two mechanical workers in a workshop were selected as impulse noise group and 163 textile workers in a textile factory as continuous noise group. SH-126 dosimeter was used to measure A weighted equal sound level of eight hours (L(Aeq.8 h)) during full working duration with equal energy rule for the selected workers. The cumulative noise exposure (CNE) was calculated by L(Aeq.8 h) and noise working years with equal energy rule for each worker. Hearing thresholds were measured by audiometer by routine method and adjusted by age and gender with GBZ49 - 2002. Hearing loss was diagnosed by GBZ49 - 2002 for each worker. RESULTS: CNE of impulse noise group [(103.2 +/- 4.2) dB (A) .year] was found lower than the continuous noise group [(110.6 +/- 6.0) dB (A) .year] by significance, P < 0.05. The hearing loss prevalence of impulse noise group (68.8%) was similar as continuous noise group (65%) without significance, P > 0.05. Strata analysis showed the hearing loss prevalence in 100 - 104 dB (A) .year and 105 - 109 dB (A) .year of impulse noise group was double than that of continuous noise group (76.9%, 90.9% vs 30.4%, 50.0%), P < 0.05. The chi-square test showed a relationship between CNE and hearing loss prevalence that was in high significance (P < 0.01) in both impulse noise group and continuous noise group. Logistic regression model showed the dose-response relationship curve of impulse noise group was left shift and sharp slope. CONCLUSION: The damage of impulse noise on hearing loss was much more than that of continuous noise according to equal energy rule of dosimeter data.