Effects of nocturnal traffic noise – sound level at subjects ́ home versus self-reported sleep disturbances

A Berlin cohort study (N=1718), with precisely calculated nightly and daily road noise exposure, shows a relevant rise of the relative risk of medical hypertension treatment for the increasing nightly equivalent sound level at the place of residence [1]. The risk was higher for adults less than 60 years in comparison with the elderly. The effect of selfreported sleep disturbance regarding hypertension does not correspond to the effect of nightly noise exposure. The unexpected finding could be caused by the non-specific and very simple question in the Spandau Health Survey (SHS). Introduction Recent epidemiological studies support the assumption that nightly traffic noise exposure plays a more fundamental role in the emergence of health disorders than noise during the daytime – particularly in relation to the cardiovascular and respiratory systems. It can be assumed that disturbed sleep patterns are impairment to health in the long run. In these terms, the usefulness of self-reported sleep disturbances is at the centre of the discussion. Method The nightly noise exposure by road traffic was gathered from a data base which was provided by the Berlin council. The data base contains noise levels separate for the day and the night calculated from traffic census data, which was checked by level measurements. With the questions “Do you suffer from sleep disturbances? " the sleep disturbance was simultaneously collected. Thus, it was possible to analyze the coincidence of health effect with the equivalent sound level as well as with the self reported sleep disturbances. The frequency of medical treatments for stress-related diseases was evaluated in the 9th cycle of the SHS (period prevalence). Logistical regressions were used for a multiple statistical analysis. As point estimators, relative risks (Odds ratios = OR) were calculated. Equivalent Sound Level at the Place of Residence and Hypertension In the SHS a significant rise of the relative risk of hypertension was calculated for the increasing nightly equivalent sound level. When only test persons who normally sleep with open bedroom window were included in the analysis, the relative risk increased to 6.1 for the nightly sound exposure with more than 55 dB (A). The results confirm the thesis that the nightly noise exposure is an environmental stressor, caused directly or indirectly by disturbed sleep. From general stress research it is well known, that the ability to cope with stress is decreased in the elderly. Therefore elderly people could be a risk group according to the nightly noise exposure. The database of the SHS was divided into age related subgroups (cutoff point 60 years) to proof this thesis on an epidemiological level. The SHS suggests a stronger association between treatments of hypertension and the nightly noise level for adults under 60 years in comparison with the elderly (see figure 1). If occupational noise is taken into account for adults under 60 years the relative risk of a hypertension treatment rises further according to the nightly noise exposure. The self-reported occupational noise is indicated as an independent and significant risk factor (OR = 2.0; CI 1.0 – 2.8). Adults, older than 60 years