Surveying the elderly about health, medical care and living conditions. Some issues of response inconsistency.

A sample of elderly persons (75-84 years old) in Sweden was surveyed twice on home conditions, health and medical care. Two data collection methods were used: interviews and a mail survey. It has been shown that it is possible to carry out a mail survey (with low non-response) among the elderly in this group. However, what about other aspects of quality? Is it really possible to use a mail survey instead of the much more expensive and complicated techniques involved in interviewing? The results show that for certain groups of variables there are fairly large differences between how respondents reply in the mail survey and in personal interviews carried out by district nurses. These differences apply both to the degree of inconsistency in answers and to shifts in marginal distributions. Among other things, more ailments are mentioned at interview. The demand for information on the elderly and the differences between the methods in the cost of gathering this information make reliability and validity studies of methods of surveying the elderly increasingly important.