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EFFECTS ON HEALTH
4.5.10 DOSE–RESPONSE CURVE: META-ANALYSIS
For a quantitative risk assessment and the derivation of guidelines for public health
noise policy a common dose–response curve is required. The risk estimates obtained
from different noise studies can be summarized using the statistical approach of a
meta-analysis. Based on the judgement criteria discussed in section 4.5.9.2, five analytic
and two descriptive studies emerged that can be used to derive a common
dose–response curve for the association between road traffic noise and the risk of
myocardial infarction. Two separate meta-analyses were made by considering the
analytic studies that were carried out in Caerphilly and Speedwell (cohort studies)
and Berlin (case-control studies) on the one hand, and the descriptive studies that
were carried out in Caerphilly and Speedwell (cross-sectional studies) on the other
hand. It turned out, as a result of the evaluation, that all these studies referred to
road traffic noise during the day (L day : 06.00–22.00) and the incidence or prevalence
of myocardial infarction as the outcome. Study subjects were men. In all analytic
studies the orientation of rooms was considered for the exposure assessment (facing
the street or not). With respect to the Caerphilly and Speedwell studies, the six years
of pooled follow-up data provided the respective information. In all descriptive studies
the traffic noise level referred to the facades that were facing the street and did
not consider the orientation of rooms/windows. All individual effect estimates were
adjusted for the covariates considered in each of the studies. Different sets of covariates
were considered in each study. However, this pragmatic approach accounts best
for possible confounding in each study and provides the most reliable effect estimates
derived from each study. The concept of meta-analysis was used to aggregate
and summarize the findings of the different studies (Olkin, 1995; Blettner et al.,
1999). The program “meta” was downloaded from the “STATA” web site for use in
the statistical package STATA (version 8.0), and for calculating the pooled random
effect estimates.
Table 4.2
Single and pooled (meta-analysis) effect estimates (odds ratios and 95% confidence intervals) of
descriptive and analytic studies on the relationship between road traffic noise level (L day ) and the
incidence/prevalence of myocardial infarction
Road traffic noise level - L day [dB(A)]
Descriptive
studies
51-55 56-60 61-65 66-70 N
Caerphilly
1.00 1.00 (0.58-1.71),[13.29] 0.90 (0.56-1.44),[17.23] 1.22 (0.63-2.35),[ 8.98] 2512
Speedwell
1.00 1.02 (0.57-1.83),[11.19] 1.22 (0.70-2.21),[12.62] 1.07 (0.59-1.94),[10.94] 2348
Pooled 1.00 1.01 (0.68-1.50) 1.02 (072-1.47) 1.14 (0.73-1.76)
Q-Test p=0.96 p=0.41 p=0.77
Analytic
studies
≤ 60 61-65 66-70 71-75 76-80 N
Caerphilly +
Speedwell
1.00 0.65 (0.27-1.57),[ 4.95] 1.18 (0.74-1.89),[17.48] --- --- 3950
Berlin I 1.00 1.48 (0.57-3.85),[ 4.21] 1.19 (0.49-2.87),[ 4.94] 1.25 (0.41-3.81),[ 3.09] 1.76 (0.11-28.5),[0.50] 243
Berlin II 1.00 1.16 (0.82-1.65),[31.43] 0.94 (0.62-1.42),[22.76] 1.07 (0.68-1.68),[18.92] 1.46 (0.77-2.78),[9.27] 4035
Berlin III 1.00 1.01 (0.77-1.32),[54.42] 1.13 (0.86-1.49),[50.87] 1.27 (0.88-1.84),[28.24] --- 4115
Pooled 1.00 1.05 (0.86-1.29) 1.09 (0.90-1.34) 1.19 (0.90-1.57) 1.47 (0.79-2.76)
Q-Test p=0.57 p=0.87 p=0.84 p=0.90
Table 4.2 shows individual and pooled effect estimates with confidence intervals
(rounded brackets), statistical weights (square brackets) for the individual studies,
and the Q-test of heterogeneity between studies. According to the Q-test, the nil
hypothesis of non-heterogeneity was never discarded. Figs 4.6 and 4.7 show odds
ratios of individual studies and the pooled estimates for the descriptive and analytic
studies.
NIGHT NOISE GUIDELINES FOR EUROPE