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It has been well documented that response rates to cross-sectional surveys have declined over the past few decades. It is less clear whether response rates to longitudinal surveys have experienced similar changes over time. This article examines trends in response rates in several major, national longitudinal surveys in the United States and abroad. The authors find that for most of these surveys, the wave-to-wave response rate has not declined. This article also describes the various approaches that these surveys use to minimize attrition.

This article updates trends from five national U.S. surveys to determine whether the prevalence of activity limitations among the older population continued to decline in the first decade of the twenty-first century. Findings across studies suggest that personal care and domestic activity limitations may have continued to decline for those ages 85 and older from 2000 to 2008, but generally were flat since 2000 for those ages 65–84. Modest increases were observed for the 55- to 64-year-old group approaching late life, although prevalence remained low for this age group. Inclusion of the institutional population is important for assessing trends among those ages 85 and older in particular.

Examination of intergenerational asthma beyond maternal asthma has been limited. The association between childhood asthma and intergenerational asthma status among a national cohort of children was examined. The genealogical sample (2552 children) participating in the Child Development Supplement of the Panel Study of Income Dynamics was studied. Multivariate regression was used to determine intergenerational asthma. Children with a parent with asthma were almost twice as likely (odds ratio [OR] = 1.96) to have asthma compared with those without a parent with asthma. Children with a parent and grandparent with asthma were more than 4 times more likely to have asthma compared with those without a parent and grandparent with asthma (OR = 4.27). Children with a grandparent with asthma were more likely to have asthma (OR = 1.52). A family history of asthma was a significant predictor of physician diagnosed asthma in children regardless of race/ethnicity and socioeconomic status. Findings support the collection of family history, including grandparent asthma status.

The decline in late-life disability prevalence in the United States was one of the most important developments in the well-being of older Americans in the 1980s and 1990s, but there is no guarantee that it will continue into the future. We review the past literature on trends in disability and other health indicators and then estimate the most recent trends in biomarkers and limitations for both the population aged 65 and older and those aged 40 to 64, the future elderly. We then investigate the extent to which trends in education, smoking, and obesity can account for recent trends in limitations and discuss how these three factors might influence future prospects for late-life health. We find that improvements in the health of the older population generally have continued into the first decade of the twenty-first century. The recent increase in the proportion of the younger population needing help with activities of daily living is concerning, as is the doubling of obesity in the last few decades. However, the increase in obesity has recently paused, and favorable trends in education and smoking are encouraging.

THE consequences of declines in mortality for the health and functioning of the nation's older adults have been the subject of much interest over the last quarter century. Indeed, spurred by Manton, Corder, and Stallard's (1993) analysis of the National Long Term Care Survey, a vast literature has developed that explicitly focuses on trends in health and disability in late life. Although initially there was disagreement, a consensus has emerged among researchers in the field that there have been improvements in most measures of late-life functioning (see, e.g., Crimmins, 2004; Cutler, 2001; Freedman, Martin, & Schoeni, 2002; Freedman et al., 2004; Kramarow, Lubitz, Lentzner, & Gorina, 2007; Manton, Gu, & Lamb, 2006; Waidmann & Liu, 2000). A recent report by the Institute of Medicine on the future of disability in America (Field & Jette, 2007) suggests that despite these improvements, the numbers of adults with disabilities will likely swell in the coming years as the large Baby Boom generation—those born during the years 1946–1964—reaches the ages associated with the highest rates of morbidity and disability. Undoubtedly, such a trend would have important implications for the provision of medical and social services, for the ability of future older adults to participate fully in society, including the workplace, and more generally for their quality of life. However, although the number of adults reaching older ages and thus experiencing elevated risks for debilitating conditions will certainly grow, there is debate about whether the Baby Boom cohort will enter later life with better or worse age-specific rates of morbidity and disability than earlier cohorts. Only a handful of studies have taken up the question of trends in health and functioning of the adult population in the decades approaching retirement, and results have been conflicting. One study, using data from the National Health Interview Survey (NHIS), found from 1984 to 1996 an increase in the prevalence of needing help with personal care and routine household activities among adults aged 40–49 and 50–59 years, although the rates of such disability were very low (Lakdawalla, Bhattacharya, & Goldman, 2004). Another study, by Zack, Moriarty, Stroup, Ford, and Mokdad (2004), using data from the Behavioral Risk Factor Surveillance System (BRFSS), found an increase from 1993 to 2001 in the proportion of those aged 35–44, 45–54, and 55–64 years who reported poor or fair health. A third study, which relied on data from the Health and Retirement Study (HRS), suggested worse health and functioning among people aged 51–56 years in 2004 compared with 1992 (Soldo, Mitchell, Tfaily, & McCabe, 2007). However, Weir (2007) concluded from his analysis of the same cohorts using a different recode of the HRS data that although early Baby Boomers were more likely to report poor or fair health than the cohort born 12 years earlier, objectively their overall health and functioning were similar. Other recent analyses of health trends among the middle-aged adult population have been more positive. Using the NHIS, Martin, Schoeni, Freedman, and Andreski (2007) found a downward trend from 1982 to 2003 in reports of poor or fair health among adults aged 40–49 and 50–59 years. Mortality rates among adults also have continued to decline in recent decades (National Center for Health Statistics, 2007). Several lessons have emerged from studying late-life health and functioning trends that are relevant to this new and growing literature focused on adults under age 65 years. First, trends are best assessed over a relatively long time horizon with multiple observations (Freedman et al., 2002); given annual variation, two data points may not necessarily constitute a trend (Crimmins, 1996). Second, different measures may move in different directions (Crimmins, 1996, 2004). For example, despite declines in most measures of late-life disability, reports of many chronic conditions among older adults have increased in recent decades (Crimmins, 2004; Crimmins & Saito, 2000; Freedman & Martin, 2000; Freedman, Martin, Schoeni, & Cornman, 2007). There are many reasons for such divergences, not the least of which is that no single indicator is a pure measure of health. For example, self-reports of chronic diseases may be influenced by access to health care, which in turn is a function of socioeconomic status. Moreover, indicators of functioning reflect the gap between an individual's capacity and the environment in which activities are carried out. Accordingly, breadth of measurement is important before drawing conclusions about the health and functioning of a cohort. Third, care must be taken to ensure that methodological threats to validity—such as low response rates, use of screening questions, changes in question wording, changes in response rates, or omission of important groups such as the institutionalized population—do not bias conclusions (Freedman et al., 2002). In this paper, we heed these lessons and expand on existing studies by assessing trends in mortality and multiple nonclinical indicators of health and functioning (including general health status, health conditions, physical functional limitations, and need for help with daily activities); by using annual data spanning from one to more than two decades, depending on the measure; and by covering the full age range of the Baby Boom. Our goal is to investigate whether the health and functioning of Baby Boomers are better or worse than those of previous cohorts in middle age.

Six hundred and twenty-six participants from the Panel Study of Income Dynamics (PSID) were interviewed via telephone ret- rospectively about life course events by either computer-assisted (CATI) event history calendar (EHC) or standardized CATI conventional ques- tionnaire (CQ) methods, randomly assigned. Experimental retrospective reports, for a reference period up to 30 years, were validated against reports provided annually from the PSID core interviews. Data quality outcome measures included variables associated with marriage, cohab- itation, employment, unemployment, residential changes, and cigarette smoking. The EHC provided higher quality retrospective reports for co- habitation, employment, unemployment, and smoking histories; the CQ provided better data quality for marriage history, although what variable was being measured, instead of which method was being used, had the biggest impact on differences in data quality. Both EHC and CQ inter- views lasted on average around one hour, with the EHC interviews being on average 10 percent longer. Interviewers preferred the EHC interviews. In both EHC and CQ conditions, respondents generally enjoyed the in- terviews, and did not find questions difficult. The costs and benefits of

To the Editor: We read with interest the article by Fuller-Thomson and colleagues (1) and their conclusion that estimates from the American Community Survey (ACS) showed an increase in difficulty with activities of daily living (ADLs) and a plateau in physical activity limitation between 2000 and 2005 for the U.S. population aged 65 years and older. Although the authors provided caveats in their interpretation of their findings, we believe that additional caution is warranted. We recently considered using the 2000–2007 ACS to assess late-life disability trends. However, we decided that because of changes in survey administration over time, we could not reliably estimate trends from the ACS. Our greatest concern was the change in interview mode. The proportion of ACS interviews that were completed via mail declined from 58% in 2000 to 52% in 2005 (and to 48% in 2007), and the proportion completed through computer-assisted interviews concomitantly increased (2–4). For people aged 16–64 years, estimates of limitation are higher using computer-assisted interviews versus mail. For example, in 2003, the differences for ADL limitation (difficulty dressing, bathing, or getting around inside) were 1.9% versus 1.8%, respectively, and for physical functional limitation (substantial limitation in walking, climbing stairs, reaching, lifting, or carrying) were 7.4% versus 6.5%, respectively (5). We were not able to find mode-specific estimates for the older population. However, if the older group experienced similar patterns, the increase in the proportion of computer-assisted interviews would likely account for some of the estimated increase in limitations. Unfortunately, the public ACS micro data sets do not provide an indicator of interview mode to use in modeling trends. Accordingly, we chose not to use the ACS. Another factor that appears to have contributed to an upward bias in the trends found by Fuller-Thompson and colleagues is aging of the population. They mentioned in their discussion the changes in the age distribution within the population aged 65 years and older from 2000 to 2005, especially the rapid increase of those aged 80 years and older. But they were not able to adjust for age in their analyses because they simply fitted regression lines across the published aggregate prevalences of limitations for each of the six survey years. We were not able to access from the internet the prevalence figures that Fuller-Thompson and colleagues used, but based on the micro data sets for each year, we calculated our own estimates of the aggregate prevalences for those aged 65 years and older, which track closely the data points graphed in figure 1 of their article. Indeed, when we fitted trend regression models using our prevalences, we found that ADL limitation increased at a rate of 1.56% per year in comparison to the 1.81% per year found by Fuller-Thomson and colleagues (calculated by dividing their regression coefficient on [year−2000] of .16 by the intercept of 8.84). However, when we calculated age-specific prevalences by 5-year age groups from the micro data, standardized the overall 65+ annual prevalence rates to the 5-year age distribution from various populations (2000, 2005, and an average of 2000–2005), and then estimated models based on these standardized prevalences, we found for ADL limitation that the p value on the trend coefficient was reduced from .005 to a range from .07 to .09, and the estimated annual change was reduced to 0.7%–0.8%. For functional limitations, the results of Fuller-Thomson and colleagues implied an annual increase of 0.37%, and we found annual change of 0.24% in our model of unadjusted prevalences and −0.14% to −0.16% for our models of age-standardized prevalences [none of the trend coefficients for functional limitations significantly different from 0, as in (1)]. As an alternative test of the importance of adjusting for age, we ran logit regressions of individual-level ADL and functional limitations on trend using the micro data set. For ADLs, our results implied an annual change of 1.67% in the unadjusted model and 0.85% in the model with 5-year age group controls. For functional limitations, the estimates were 0.34% and −0.23%, respectively. (All logit trend coefficients were statistically different from 0.) Accordingly, it appears that controlling for age results in a halving of the rate of increase for ADLs and in a trend downward, as opposed to upward, for functional limitations. We applaud Fuller-Thomson and colleagues for their attempt to shed light on the most recent disability trends and especially for their care in accounting for the institutionalized population. We also agree that tracking trends going forward is critical. However, estimated trends may be contaminated by changes over time in a variety of factors, some of which they note, such as survey design and administration, use of proxies, population coverage, question wording, and age distribution (6). Moreover, differences across surveys may also affect comparisons of trends (7). In sum, we do not think that the analysis of the ACS by Fuller-Thomson and colleagues provides sufficient evidence to reach even tentative conclusions about recent late-life disability trends.

Objective. We sought to determine whether socioeconomic and racial/ethnic disparities in prevalence of disability over age 70 have widened or narrowed during the past 2 decades. Methods. We used data from the 1982–2002 National Health Interview Surveys, which are nationally representative cross-sectional surveys of the noninstitutionalized population of the United States. Participants included 172227 people aged 70 years and older. The primary outcome measure was the average annual percentage change in the prevalence of 2 self-reported disability measures: the need for help with activities of daily living (“ADL disability”) and need for help with either ADL or instrumental activities of daily living (“any disability”). Results. All groups experienced declines in the age- and gender-adjusted prevalence of any disability during the 1982 to 2002 period. However, the average annual percent declines were smaller for the least advantaged socioeconomic groups. Differences in trends across racial/ethnic groups were not statistically significant. ADL disability prevalence decreased for the more advantaged groups but increased among the lowest income and education groups. Non-Hispanic Whites and minorities experienced similar average annual percent declines in ADL disability. Conclusions. Racial/ethnic disparities in old-age disability have persisted over the last 20 years, whereas socioeconomic disparities have increased.

Objectives. We addressed three questions: Have recent improvements in old-age disability been mirrored in changes in self-reported general health status? Are general health status trends similar for younger and older Americans? Have changes in general health status been uniform across demographic and socioeconomic groups? Methods. Using logistic regression, we analyzed data from the 1982–2003 National Health Interview Surveys (n ¼ 1,445,872 aged 18–69; n ¼ 178,384 aged 70 and older). Results. The proportion of people aged 70 and older reporting disability declined at 1.38% per year and the proportion 70 and older reporting poor/fair health declined at 1.85% per year. There was less of a decline in reports of poor/fair health at younger ages. Trends for the 18–69 population showed widening health disparities by income but narrowing of the race/ ethnicity and education gaps. In the older population, there was no change for those aged 80–84 and 85 and older, the race/ ethnicity gap persisted, and both education and income differentials widened over time. Discussion. Declines in proportions reporting poor/fair health among the older population in recent decades mirror declines in disability. Although the younger population has not experienced such progress, its prevalence of poor/fair health is low throughout the 21-year analysis period. Of concern are the growing socioeconomic disparities in health for both younger and older populations.