We used data from participants in the Framingham Heart Study (FHS). The FHS is a population-based, longitudinal, observational cohort study that was initiated in 1948 to prospectively investigate risk factors for cardiovascular disease. Four cohorts, mostly representing different generations linked to an original cohort, are included in the entire FHS study. Participant data, collected every two to four years, includes physical examinations, laboratory tests, noninvasive cardiac and vascular testing, battery testing (such as the Mini-Mental status exam), questionnaire results, and basic demographic information. For the purposes of the analyses reported here, exam waves for the Original cohort were aligned with those of the second-generation Offspring cohort, so that all subjects were treated as having been examined at just seven waves. The Offspring Cohort, initiated in 1971, is the source of this study's “principals,” or focal individuals in the network (16). However, other FHS participants are included when listed as social contacts by the principals, which will be referred to as “contacts.” Therefore, whereas principals come only from the Offspring Cohort, contacts are drawn from the entire set of both the original and offspring cohorts.
