Nonresponse and intensity of follow-up in an epidemiologic study of Vietnam-era veterans.

Characteristics of nonrespondents, respondents who were easy to locate, and respondents who were hard to locate were examined with the use of data from a telephone health survey of male, US Army, Vietnam-era veterans. Of 17,867 eligible men discharged from active military duty in the late 1960s and early 1970s, 15,288 (86%) were successfully located and interviewed during 1985-1986. Veterans who could not be located were more likely than respondents to possess baseline characteristics predictive of increased mortality. In contrast, subjects who were located but refused to be interviewed were similar to respondents. Among veterans who were interviewed, those who were hardest to locate had the highest prevalence of known risk factors for diminished health status and reported many health problems with higher relative frequencies than respondents who were easier to locate. Odds ratios comparing the prevalence of each of 11 health outcomes in men who had served in Vietnam with that in men who had served elsewhere did not vary appreciably by intensity of follow-up. In particular, the subgroup of respondents that was located and interviewed within 2 weeks of initiation of follow-up (comprising 25% of all respondents) produced odds ratios for 10 of the 11 outcomes that were not appreciably different from odds ratios based on all respondents.

Effects of an advance telephone call in a personal interview survey.

During October and November 1982, 1,260 Medicare-eligible senior citizens were interviewed in a survey focusing on health care of the elderly. As part of the survey, an experiment was conducted in each of the three survey sites to determine the effects of an advance telephone call to schedule an appointment for a personal interview. One random half sample in each site was sent a lead letter, followed by a telephone call to schedule a personal interview. The other half sample was sent a lead letter followed by a personal contact, with no intervening telephone call. Telephoning to arrange an appointment for a personal interview resulted in a 20 percent saving in data collection costs with only a 1 percent decrease in response rate.

Personal versus telephone surveys for collecting household health data at the local level.

Personal and telephone interview surveys were conducted simultaneously during 1981 in the same area (four counties in the area of Tampa Bay, Florida) and utilizing the same interview schedule. Following completion of the surveys, validity checks were made with the medical providers reported by a subsample of respondents to each mode. The telephone survey yielded a lower response rate but cost less than half the personal interview. There was some evidence of nonresponse bias in the telephone survey, and some relatively minor differences in responses were found between the two modes, but there was no conclusive evidence that the response differences resulted from mode effects. Telephone respondents appeared to be somewhat more accurate in their reporting of visits to medical providers, although accuracy comparisons must be interpreted with caution in view of the disparate success experienced for the two modes in securing permission forms for the release of medical record information.