Surveys

All cohorts have been followed up in quite regular intervals through postal questionnaires. Several surveys included lab measurements and interviews in nested subsamples (Table 2).
 

Response rates

Response rates were good for initial surveys but steadily declined in later follow-ups (Table 3). A major reason for this attrition has been changes in addresses. Currently we are trying to obtain updated addresses for all cohorts so as to reach as many members of the original samples as possible.