Ethnic status and participation in longitudinal health surveys.

Ethnic differences in survey participation and their effects on self-reported physical and psychiatric health status measures were examined in a longitudinal health study in Alameda County, California, in 1978 following two time intervals. Blacks and Mexican-Americans were more likely than whites to refuse to participate in follow-up surveys and were more difficult to trace when the time interval between interviews was long. With the exception of age, demographic characteristics were not consistently associated with participation status either across ethnic groups or across time periods. Self-reported psychiatric and physical health status were not statistically associated with participation status in any ethnic group for either time period, despite differential participation by ethnicity.