Selection of neighborhood controls for a study of coronary artery disease

This report describes the selection process for a neighborhood control group recruited between February 1985 and July 1986 to augment a hospital-based case-control study investigating the relation of traditional and nontraditional risk factors to coronary artery atherosclerosis. A total of 219 cases with angiographically defined coronary artery disease residing within a 60-mi (96-km) radius of Winston-Salem, NC, were assigned to surveyors to be matched. Thirty-seven per of the study population were rural, 92% were white, 58% were male, and 52% were older than 50 years of age. One hundred and eighty-seven controls were age-(+/- five years), sex-, and race-matched pairwise to cases. After locating the residence of the case, the surveyor systematically visited neighboring households to ascertain eligibility status of residents. To achieve a match, a maximum of three visits was made to the neighborhood; up to 25 households were surveyed per visit. Refusal rate was less than 5% of eligible matches. Young white urban males were the easiest to match, while rural females, especially older persons, were the most difficult. Average time to complete an assignment included 129 minutes for travel, 237 minutes for surveying the neighborhood, and 62 minutes for clerical tasks. Average distance traveled was 85 mi (136 km) per case. As expected, the time and distance to complete a case were greater in rural than urban areas. The average cost per case was $122.97.