Sound Reactions? : Modelling the influence of socioeconomic status, noise annoyance, noise sensitivity and sleeping problems on subjective health complaints and cardiovascular disease.

Abstract

1.5 million people in Norway (1/3 of the population) are exposed to transport noise levels exceeding recommended values. How do people react to such noise? How do environmental characteristics and socio-economic factors contribute in explaining exposure to and annoyance from road traffic noise? What is the role of personal factors such as noise sensitivity? And finally, are there any negative health consequences? The aim of this thesis was to investigate these research questions.<br> The current thesis belongs to the field of Psychology; more specifically to Environmental Psychology. Environmental Psychology emphasizes that persons and environments, even if they are separate entities, are continually involved in a series of interactions, both being mutually shaped by the encounter with the other. This focus on interactionalism implies an increased awareness about the causal relationship between contextual background variables and the outcome variables under scrutiny. In the current thesis, Structural Equation Models (SEM) are chosen to investigate the interrelationships between variables. By forcing the researcher to make more explicit assumptions about cause and effect, SEM helps to elucidate the quantitative expression of a given theoretical model.<br> The thesis used data from two major data sets. Data set 1 (applied in articles I-IV) stems from 17 local environmental surveys carried out between 1987 and 2001, comprising a total of 19 000 respondents from the cities of Oslo and Drammen. The studies were conducted in 50 different subareas. Data set 2 (applied in article V) derives from a socio-acoustic survey of 3262 persons in Oslo. Response rates were in the range 40-50% in data set 1, and 60% in data set 2. In both data sets noise levels inside and outside each participant’s dwelling were assessed using the Nordic Prediction Method for road traffic noise using digitalised terrain data on buildings and noise screens in three dimensions. The precision of the estimated noise exposure values is deemed to hold a higher quality than what is normally associated with noise mapping software.<br>. General relationships between noise exposure levels and annoyance from road traffic in Norway were established in paper I. Half of the population find road traffic noise highly annoying at 70 dB and somewhat annoying at 58 dB. These curves indicate that even if the respondents react somewhat more strongly to a given noise level than do respondents surveyed in other European studies, the results fits well with previous results on noiseannoyance relationships.<br> Noise level explains only about 20% of the variance in noise annoyance. Hence, there are a range of other variables that might potentially contribute to explaining why some people find noise bothersome, and others not. In paper II we were interested in the impacts of having an adverse neighbourhood soundscape. We therefore used the highest equivalent noise level attained within a radius of 75 meters of the apartment, in order to calculate a neighbourhood maximum difference indicator, Ldiff.max. The Ldiff.max indicator explains a considerable amount of noise annoyance in addition to exposure at the most exposed facade, the worst cases can add upwards to 7 dB the exposure level.<br> In paper III we investigated whether income may influence annoyance levels directly, by high SES residents having better resources for dealing with a given noise level, or indirectly, by giving high SES residents a choice to live in less noisy areas. The SEM model that was developed helped to illustrate the dynamics of how noise annoyance is produced and socially distributed in a community. Income was only (indirectly) related to noise exposure in a medium-sized city. In a larger metropolitan area, other factors related to residential quality seem to override any potential relationship between income level and noise exposure. In line with previous results no (direct) relationship was found between noise annoyance and income.<br> The models were further elaborated in papers IV and V. These models were instrumental in establishing relationships between noise, sleep disturbances, subjective health complaints and cardiovascular disease. No relationship was found between noise exposure or annoyance and cardiovascular disease. The close ties between noise sensitivity and subjective health complaints were used as an argument for paying close attention to the role of general vulnerability in future studies of noise health relationships. Sleeping problems due to road traffic noise have been suggested as a major contributor to stress-related negative health outcomes. We show that road traffic noise is only a moderate contributor to overall sleeping problems, and that subjective health complaints are linked to both sleeping problems and noise experience.<br> In line with core theoretical principles of environmental psychology the results of these papers point to the importance of looking at the noise health relationship in a broader environmental and psychological context. Future research should combine large-scale community studies with good quality individual exposure assessments. Alongside the pursuit of further knowledge of potential health effects of noise, we should therefore strive to gain further understanding of the causal mechanisms, with particular focus on the psychological and behavioural effects of noise.