Traffic noise, insomnia and risk factors in the pathway to cardiovascular disease

Increasing traffic and urbanization makes traffic noise a growing public health problem. About 1.5 million Norwegians are exposed to noise levels outside the residence that exceeds the recommended values of 55 dB. Estimates from the World Health Organization (WHO) show that traffic noise contributes to at least one million healthy life years lost annually in Western Europe. Noise induced sleep disturbances constitutes the greatest burden. Studies in recent years also show an association between traffic noise and increased risk of hypertension and cardiovascular disease. Some studies indicate that especially the noise at night may be the most critical with respect to health hazards due to noise. The immediate effects of noise exposure on sleep are well documented. The long-term consequences of night noise on health are however little studied. The aim of the project was to gain more knowledge about how traffic noise, especially noise at night, affects people's health. In this project we employed epidemiological methods to look at the relationship between traffic noise and various health outcomes. One of the objectives was to investigate the association between noise on sleep quality and the use of drugs for sleep problems. Another aim was to investigate the association between exposure to traffic noise and known risk factors for cardiovascular disease including body mass index (BMI), waist circumference and waist-hip ratio. We used data from the Oslo Health Study (HUBRO, 2001-01) and the follow-up survey Health and Environment in Oslo (HELMILO, 2009-10). In addition to a medical examination in which the HUBRO participants submitted blood and got their height, weight, waist circumference and blood pressure measured, questionnaire data about their health and lifestyle were collected. The HELMILO survey included only filling out a questionnaire and information about residential and local environment, noise annoyance due to traffic, sleep quality, noise sensitivity, lifestyle, physical and mental health was collected. Furthermore, information collected in HUBRO and HELMILO was linked to socio-demographic data from Statistics Norway (SSB) as well as sleep medication use from the Norwegian Prescription Registry. For all people included in the survey we assessed the annual average level of traffic noise (Lden) and the night-time traffic noise (Lnight) outside the residential address. We collaborated with a group of researchers from Karolinska Institutet in Stockholm. They used data from a Swedish cohort (SDPP, N = 5712) to investigate the relationship between traffic noise and obesity markers in a similar way as carried out in the Norwegian study. The results show that road traffic noise at night is associated with symptoms of insomnia such as difficulty falling asleep and premature awakenings. This suggests that night noise can lead to insufficient sleep, which can be associated with a variety of other health problems. The results also showed an association between traffic noise and use of prescribed sleep medications. We found no association of traffic noise at night and self-reported use of sleep medications. Results from both the Norwegian and the Swedish study suggest an association between road traffic noise and obesity. In the Norwegian study, we found that women who perceive themselves as highly noise sensitive had 24 percent increased risk of obesity (waist-hip ratio> 0.85) per 10 decibels increase in traffic noise. However, no similar association was found among noise sensitive men. The relationship between traffic noise and obesity was stronger among those who had been exposed to noise over several years. We had hypothesized that a possible causal relationship between noise exposure and obesity could be mediated by disturbances of sleep. Our results only partially support this assumption. We found no increased risk estimates among those reporting sleep problems, but among men with bedroom facing a road the relationship was stronger. However, it is important to emphasize that traffic noise may have negative effects on sleep, as shorter awakenings, sleep stage changes and temporal pulse and blood pressure increases, which are not captured in self-reported measures of sleep quality. The Swedish study found an association between traffic noise and waist circumference and waist-hip ratio. They also found an increased risk of obesity in people who in addition to being exposed to road traffic noise were exposed to noise from aircraft and railway traffic. The findings suggest that an increased health risk due to noise may be most pronounced in certain vulnerable groups. The results also indicate that there may be gender differences in the health effects of noise. The results of this project have contributed to a greater understanding of the effects of long-term exposure to traffic noise on sleep and health and possible mechanisms for noise related cardiovascular risk.

Long-term exposure to road traffic and aircraft noise has been shown to be associated with increased risk of cardiovascular symptoms and disease. A hypothesis is that nighttime noise exposure leads to sleep disturbances and activates the sympathic nervous system. After years of exposure these changes may lead to dysregulation and permanent physiological changes that increase the risk of cardiovascular disease (CVD). Further, cardiovascular responses to noise during sleep have shown little or no habituatio n. The main aim of this project is to elucidate how traffic noise can affect insomnia and different risk factors in the pathway to CVDs. The relationship of long-term exposure to nocturnal traffic noise with sleep disturbances, insomnia, use of sedatives, tranquilizers and anti-depressive drugs, will be examined. Also the potential relationship between long-term exposure to traffic noise and body mass index, waist-hip ratio, serum glucose and type 2 diabetes will be investigated, and whether noise-induced sleep disturbances and insomnia may be intermediate factors in this relationship. Another objective is the relationship between long-term exposure to traffic noise and use of antihypertensive drugs. The associations between traffic noise exposure and ris k factors for CVDs will be studied in a longitudinal design. Data from HUBRO and The Health and Environment study in Oslo (a follow-up questionnaire study in 2009, http: //www.fhi.no/helmilo) will be used and linked to the Norwegian Prescription Database. Using the geographical coordinates for each participant's home addresses during 2000-2006 and information on bedroom location, long-term exposure to residential traffic noise will be assigned. The project will add knowledge to the role of traffic noise i n developing insomnia, and further to type 2 diabetes and CVD, with special focus on risk factors. We may also reveal susceptible subgroups to health effects of traffic noise.