There is growing public concern about adverse effects of traffic noise on health, as research has found that traffic noise increases the risk for cardiovascular diseases. Noise is thought to act as a stressor and disturbs sleep. Though this potentially could increase the risk for other major diseases, noise effects on other than the cardiovascular diseases are virtually unexplored.The main objective of this project is to investigate if long-term exposure to road traffic noise is detrimental to various health outcomes in susceptible groups, i.e. children and elderly. Outcomes in children include low birth weight, infections and cognitive performance, and in elderly outcomes include diabetes, cancer, cancer survival, health-related quality of life and health behaviour.The basis of this proposal is two unique Danish cohorts of, respectively, 57,053 elderly and 101,042 children (a national birth cohort). Historic and present residential addresses for all cohort members will be obtained through linkage with the nationwide Central Population Registry, and exposure to road traffic noise and air pollution will be calculated by validated models at all addresses.The health outcomes will be obtained from cohort interviews/questionnaires or found through linkage with unique, nationwide, population-based health registers, such as the Danish National Hospital Registry, the Diabetes Registry and the Cancer Registry.Data will be analysed using a number of statistical analyses depending on design and the character of the endpoint variable. All analyses will be adjusted for potential confounders such as air pollution, smoking and education.Within the EU, 30% of the population lives at locations where the 55dB WHO noise limit is exceeded. Knowledge of harmful effects of noise is, however, limited. The results of the proposed research have a high potential to influence the content and time schedule of noise action plans in the EU member states.