Participants discussed the point made in the session that a more disabled person might take longer to do something than a less disabled person. In experiential sampling, that person is more likely to be picked up doing the specific activity than others. Is that a length-biased sample of activities or a measure? The issue is what is being measured—the proportion of people doing activities and the length of time on activities are two different questions.
Another use of the time-use method is to track changes in patterns of activity or participation over time, which may reflect changes in health as well as disability status. But at a point in time, how does one determine what is normative and what may be reflective of poor health or disability? Still another issue raised concerns how to interpret the responses if one asks people on how many of the past 7 days they have done some activity that is considered elective. They may choose to do it or not do it. How does one know whether the decision to do it or not to do it is related to their functioning or that they are just not interested in the activity, such as socializing or going to meetings? There are a couple of ways to answer that question: asking people whether they do an activity as much as they like to, as well as linking it to health-related reasons; or asking people what it is that they value and then tracking their participation in those activities. Questions can be individualized to what people say is important to them.
A participant commented that late-life disabilities are a manifestation of the life-long accumulation of activities. The data now available in the United States do not allow a life-course study of how early exposures to negative factors in personal traits, and also the environment, result in any late-life disabilities. The earliest data available on late life are maybe from HRS.
Guralnik observed that in contrast to the situation in the United States, the British have birth cohorts, the oldest of which is now over 60 years old. They also have cohorts that started a little bit later in life that are now aged. The evidence is clear that early life factors play a very large role in mid-life and late-life functioning. Participants agreed that such cohorts are invaluable for studying the life-long development of disabilities. In some cases, existing cohorts could be used if there are mid-life or earlier data and one can recontact people when they are older. In that vein, it was noted that one of the rationales for adding the study of disability to the PSID is that the panel study is over 40 years old now and does have some predictive measures, mostly economic ones, of distress in early life.