Health effects of road traffic noise in childhood and adolescence

Traffic noise is an increasing environmental exposure, primarily as a consequence of continuous urbanisation and growth of the transport sector. The burden of disease from noise is the second highest in Europe among all environmental exposures, after air pollution, and WHO recently proposed more strict environmental noise guidelines. Evidence on noise effects early in life is limited, although existing data indicate an onset of harmful effects in childhood and adolescence, with a possible role of exposure already in utero. The overall aim of this thesis was to investigate effects of pre- and postnatal exposure to road traffic noise and/or maternal occupational noise exposure during pregnancy on birth outcomes as well as on certain cardiovascular, metabolic and respiratory health effects during childhood and adolescence. All studies in this thesis were based on the BAMSE birth cohort, which includes more than 4000 children from Stockholm County born during 1994-1996. Individual assessment of residential exposure to noise from road traffic was based on a newly developed database containing longitudinal information on determinants of traffic noise levels in Stockholm County. Data on health outcomes and covariates were obtained from questionnaires, medical examinations and health registers. Road traffic noise exposure was not associated with saliva cortisol in 16-year-olds. However, the levels were markedly increased in the highest exposure group among those very annoyed by road traffic noise. Furthermore, BMI was increased in school children in relation to road traffic noise exposure, with increments of 0.11 kg/m2 and 0.20 kg/m2 per 10 dB Lden in the age groups 8-11 and 12- 16 years, respectively. Maternal noise exposure during pregnancy was not related to birth weight, however, an inverse association was observed between maternal road traffic noise exposure during pregnancy and preterm birth (OR 0.72, 95 % CI 0.59– 0.90 per 10 dB Lden). There was no clear association between road traffic noise exposure and systolic or diastolic blood pressure, but a tendency to elevated systolic blood pressure was noted in 16-year olds when their mother was heavily exposed to noise in the workplace during pregnancy. Asthma and wheezing during childhood and adolescence were generally not related to road traffic noise exposure in infancy or to maternal noise exposure during pregnancy. However, there were tendencies towards increased risks for asthma ever up to 16 years with residential road traffic noise exposure in infancy ≥55 dB Lden (adjusted OR=1.22; 95 % CI 0.90-1.65), as well as with prenatal occupational noise exposure ≥80 dB LAeq8h (OR=1.18; 95 % CI 0.85-1.62). In conclusion, our findings suggest effects of road traffic noise exposure on saliva cortisol levels, in combination with annoyance, and on BMI development. However, no clear associations were observed for blood pressure in adolescence or asthma/wheezing from childhood to adolescence