摘要：Using questionnaire is a common, efficient and
cheap way to collect data in population-based epidemiological studies. However, there
is a general trend of declining response rates leading to a higher risk for
bias affecting the validity of results. Use of anonymous questionnaires and/or
other ways of distributions, e.g. via schools instead of postal, may increase
response rates, but can also lead to other types of systematic errors. This
study indicates that results from cross-sectional questionnaire studies differ
depending on distribution method and whether the survey is anonymous or not.
Also the official purpose of the survey may affect the outcome. When studying
well-known risk-factors and health effects,
potential methodological problems like reporting bias must be considered in
cross sectional studies.
关键词：Questionnaire; Asthma; Longitudinal Study; Home Environment; Children; Dampness; Smoking; Bias
