Non-response pattern and bias in a community-based cross-sectional study of cognitive functioning among the elderly

Abstract

The demographic, health, and mental functioning characteristics of nonresponders to a community-based cross-sectional study of cognitive functioning among the elderty in Amsterdam, the Netherlands (Amsterdam Study of the Elderly (AMSTEL), October 1990 to May 1991), were examined and compared with responders. The randomly selected age-stratified (65-74, 75-84 years) sample was drawn from nonresponders listed with a subsample (n = 8) of general practitioners whose lists served as the sampling frame for the main study. The general practitioners approached and interviewed the respond-ing nonresponders using the same standardized questions that were used in the main study. Nonresponders (n = 115) and responders (n = 999) from the same medical practices were compared by means of chi-square and odds ratios. Compared with re-sponders, these nonresponders more often reported a history of psychiatric illness, heart attack, stroke, and diabetes, and were more likely to be unmarried, to have a lower education, and to do poorly on the cognitive test (odds ratio = 1.6, 95 % confidence interval 1.0-2.6). Most significant physical and mental health differences by response status were seen among the persons aged <75 years and not among those aged a7