Differences between respondents and non-respondents in a population-based cardiovascular disease study.

The differences in cardiovascular health status between participants and non-participants were examined in a population-based cardiovascular study. Telephone interviews with non-respondents revealed generally more cardiovascular disease but less hyperlipidemia and family history of cardiovascular disease. Non-respondents did not differ regarding known hypertension, diet or drug therapy for hyperlipidemia, or egg use. Non-respondents were more likely to be cigarette smokers. Because the amount of non-respondent bias in the study was small while the response rate was high, respondents were generally representative of the target population. However, the observed differences could have produced spuriously high estimates of risk factor prevalence, low estimates of disease prevalence, and biased relative risks if the non-response rate and/or the baseline differences had been considerably larger.