From the Department of Preventive Medicine and Biometrics, University of Colorado School of Medicine, 4200 East Ninth Avenue, Box C245, Denver, CO 80262 (e-mail: richard.hamman{at}UCHSC.edu).
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ABSTRACT |
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activities of daily living; aging; ethnic groups; Hispanic Americans; population characteristics
Abbreviations: ADL, activities of daily living; IADL, instrumental activities of daily living; MMSE, Mini-Mental State Examination; SLVHAS, San Luis Valley Health and Aging Study
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INTRODUCTION |
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Sociocultural factors and people's appraisals of symptoms and health can affect functional status (6). We previously found moderately greater prevalence of disability among Hispanic than among non-Hispanic White elderly in the San Luis Valley Health and Aging Study (SLVHAS) (7
, 8
). Hamman et al. (7
) reported greater Hispanic dependence in activities of daily living (ADL) among people aged 65 years and older (age- and gender-adjusted Hispanic to non-Hispanic White odds ratio = 1.4, 95 percent confidence interval: 1.0, 1.9). Shetterly et al. (8
) found the community-dwelling Hispanic cohort aged 60 years and older to be significantly more likely to report the need for assistance with instrumental activities of daily living (IADL) (age- and gender-adjusted Hispanic to non-Hispanic White odds ratio = 1.6, 95 percent confidence interval: 1.3, 2.1).
Prevalence has two components: incidence and duration. A higher incidence of disability and/or lower rates of recovery among Hispanic persons over time would result in greater prevalent disability. Differentially lower Hispanic mortality rates leading to more years of life in a disabled state would also increase prevalence among Hispanic persons. Exploring these possibilities requires estimates of incident disability, recovery, and mortality. Previous studies have provided some information about incidence and recovery rates in older populations, but few are ethnic specific, and we found no studies that compared Hispanic with non-Hispanic White rates (4, 9
12
). Two national studies reported differences in mortality rates among the elderly of different racial/ethnic groups; both found lower rates among Hispanic elderly than in other populations (13
, 14
).
This report documents the incidence of ADL and IADL dependence, recovery from dependence, and mortality in the biethnic SLVHAS population during nearly 2 years between baseline and the first follow-up assessment (8). It examines the degree to which these patterns of incident dependence, recovery, and mortality explain the observed excess Hispanic prevalence of functional dependence previously reported (7
, 8
).
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MATERIALS AND METHODS |
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Bilingual interviewers collected responses from 1,358 community-dwelling participants and 75 nursing home residents (81.5 percent response rate). The baseline response among nursing home residents was high and did not differ by ethnicity; among community dwellers, those who refused were more likely to be non-Hispanic White. Persons who refused at baseline were less likely to have any reported ADL difficulty and were slightly more likely to be at least age 80 years. They did not differ significantly from respondents by sex, education, self-rated health, or hospitalization in the previous year (8).
Interviewers revisited the respondents approximately 22 months later and administered a shortened version of the baseline assessment. By that time, 147 persons had died (105 community dwellers, 73 Hispanics, and 75 females), and 98 refused the follow-up visit (96 community dwellers, 59 Hispanics, and 54 females). Interviewers collected data from the remaining 1,188 study members (92.4 percent of the baseline cohort alive at follow-up), including 31 nursing home residents. We excluded from this analysis those who did not supply ADL or IADL information at baseline or follow-up. Subjects remaining for ADL analyses included 1,115 community dwellers and 30 nursing home residents. For IADL analyses, 1,099 community dwellers provided sufficient information.
Among community-dwelling and nursing home survivors at follow-up, those who refused (7.9 percent of Hispanics and 7.2 percent of non-Hispanic Whites) had significantly lower baseline cognition scores (p = 0.001) and somewhat lower levels of education (p = 0.13) than did respondents. They did not differ significantly by sex, age, or baseline reports of ADL difficulty or dependence, hospitalization in the past year, or number of chronic diseases.
Protocol
All interviewers were bilingual, and Spanish-translated forms were available. The Mini-Mental State Examination (MMSE) of Folstein et al. (16) measured cognitive status. Participants who scored 18 or higher on the MMSE completed the full protocol. A limited number of persons with literacy or vision difficulties who scored between 11 and 17 were judged cognitively capable of completing the entire protocol. All other participants who scored less than 18 completed the physical examination and selected performance tasks; a primary caregiver or close relative with knowledge of recent functioning and medical history, if available, supplied a subset of the remaining information. Hispanic respondents more often required proxy assistance than did non-Hispanic White respondents (12.1 vs. 6.1 percent of this study's sample at baseline, 20.9 vs. 12.0 percent at follow-up). This difference reflects a similar ethnic disparity in MMSE scores that correlated with lower levels of education among Hispanic elderly. An earlier report found that both education (p < 0.001) and ethnicity (p = 0.01) contributed significantly to the variation in MMSE scores in this population and that eliminating culturally sensitive items from the MMSE reduced, but did not eliminate, the ethnic disparity (17
).
Reported disability
Disability questions came from the 1984 National Health Interview Supplement on Aging (18): "Because of a health or physical problem, do you have any difficulty" with ADL tasks (eating, bathing, dressing, toileting, transferring between bed and chair, walking across a room, and getting outside) and similarly with IADL tasks (shopping, transportation, preparing meals, using the telephone, taking medication, managing money, and doing light and heavy housework). Respondents who indicated any difficulty further rated their level of difficulty as some, a lot, able with help, or unable to do. We defined disability as dependence, that is, needing assistance with or being unable to do the task. The IADL difficulty question had an additional possible response, "does not do for other reasons" (e.g., for some men, preparing meals). We did not classify these responses as dependence because they typically indicate custom rather than ability (19
, 20
).
Nursing home residents were assumed to be IADL dependent in at least one task and so were not asked about IADL disability. Almost all (92 percent) reported ADL dependence at baseline as well, and none recovered from dependence. We therefore included nursing home residents only in analyses of mortality.
Statistical methods
Computation of density rates (21) for incident disability and recovery from disability assumed that relevant events occurred at the midpoint between the baseline and follow-up interviews. Person-years at risk prior to death were based on actual dates of death. The SAS analysis package version 6.12 (SAS Institute, Inc., Cary, North Carolina) and PEPI version 3.0 (22
) were used for analysis.
Density rates were adjusted to the age distribution of the subset of the population eligible for the particular outcome. Age-standardization weights therefore differed by outcome, precluding comparison of rates across outcomes but allowing comparisons within outcomes. This constraint seemed preferable to the distortion (e.g., overestimating incidence) that would be introduced by, for example, applying age-specific incidence rates to the age structure of the entire older and already partially disabled population rather than to the generally younger, incidence-eligible subgroup free of dependence at baseline.
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RESULTS |
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Change in functional status
During the approximately 22 months between visits, persons who survived could develop functional dependence, recover from existing dependence, or continue as at baseline. Table 2 provides numbers of events and person-years of eligibility for these events and mortality. Table 3 presents age-adjusted rates of incident ADL and IADL dependence, recovery, and mortality, by sex and ethnicity.
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A total of 186 (23 percent) of the 806 persons with no IADL dependence at baseline reported dependence at follow-up. Hispanic respondents had higher, but not significantly different, IADL incidence rates than did non-Hispanic White respondents (16.2 compared with 13.4 per 100 person-years; p = 0.17). As with ADL dependence, women had a slightly greater risk than did men.
Recovery from dependence. Thirty-four (23 percent) of the 151 community-dwelling persons with ADL dependence at baseline reported no dependence at follow-up. Similarly, 47 (16 percent) of the 293 community-dwelling persons with baseline IADL dependence did not report dependence at follow-up. Hispanic females had substantially lower rates of recovery than did other sex-ethnicity groups, but the small number of persons eligible for recovery limited the power to identify statistically significant differences.
Mortality. Hispanic and non-Hispanic White mortality rates in community-dwelling residents were similar. Men had significantly higher rates than did women, due to higher rates among non-Hispanic White men aged 80 years or older (17.2 per 100 person-years) and lower rates among non-Hispanic White women in that age group (5.5 per 100 person-years).
Mortality rates in the total population that included nursing home residents were higher than those in the community-dwelling cohort, especially among non-Hispanic Whites, because a greater percentage of non-Hispanic White than of Hispanic elderly resided in nursing homes (data not shown). As in the community-dwelling cohort, rates for males were higher than those for females. Sex-ethnicity subgroups showed the same sex-related differences as in the community-dwelling sample.
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DISCUSSION |
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Patterns of incidence, recovery, and mortality
This study found overall age-adjusted incidence rates of 9.5 for ADLs and 15.1 for IADLs, both per 100 person-years. The only other study of ADL incidence in Hispanic elderly that we found reported a rate only about one fourth as large, but that study examined a less rural and physically more capable population (9). Two-year studies of Longitudinal Study on Aging data also reported ADL rates about one fourth as large and IADL rates about half as large as we found (4
, 10
).
Our higher incidence rates may reflect an actual greater functional burden due to environmental as well as social and cultural factors specific to the rural SLVHAS study population. The differences in reported rates may, however, also reflect differences between studies or measurement reliability. Earlier studies differed from this one and each other in purposes of the analyses, characteristics of populations, definitions of disability (23), the number of activities assessed (the greater the number, the more likely the identification of any disability), and the extent of dependence on proxy response (24
). Unreliability of response, if present, could distort rates. Retesting a sample of this study's population (n = 60) indicated only moderate reliability for the ADL questions (kappa = 0.56). Attribution of ADL incidence for 43 percent of respondents was based on reports of newly identified dependence in only a single activity, which might have resulted from test-retest unreliability over the span of the study. Conversely, however, the majority of respondents reported new dependence in more than one activity, a finding that suggests real new disability.
ADL recovery rates reported here correspond with those found in studies lasting 2 years (12, 25
). Longer studies (4
, 10
) reported lower rates, but decline during the later years may well have masked or erased earlier periods of recovery.
Other studies have reported mortality rates similar to the 4.8 per 100 person-years found here (4, 10
, 12
14
). Two national studies that compared Hispanic and non-Hispanic White mortality rates (13
, 14
) reported significantly higher rates for non-Hispanic Whites than for Hispanics, a pattern that our study does not confirm, although we found a trend in that direction.
Determinants of prevalence
We examined the possibility that greater incident dependence among Hispanic elderly, combined with lower mortality rates and decreased recovery from dependence, would explain the previously observed greater Hispanic prevalence of functional dependence in this community-dwelling population. We found a slight, nonsignificantly greater Hispanic experience of incident IADL dependence and no ethnic difference in ADL incidence among community-dwelling study members. Hispanic women reported lower rates of recovery than did other sex-ethnicity groups, although the differences were not statistically significant and the numbers were small. There were no significant ethnic differences in mortality. Men experienced significantly higher mortality rates than did women, while women tended to report a greater risk of dependence in ADL. Sensitivity analyses estimating the prevalence of disability over time, using this study's ethnic-specific incidence, mortality, and recovery confidence interval rate boundaries as input (analyses not shown, but available from the authors), suggest that prevalence comparisons of Hispanics with non-Hispanic Whites are sensitive to incidence rates (only in males) but not to mortality or recovery rates. These results do not offer clear explanations for the observed excess Hispanic prevalence previously reported.
Burden of disability
Several issues relevant to the community emerge from these analyses. It appears that the burden related to functional disability is greater in this rural community than in others. That burden is larger among Hispanic elderly because of higher baseline prevalence, although it is not increasing more rapidly. The impact on the Hispanic community caregivers is even greater because fewer Hispanic elderly use nursing homes, as also noted in earlier SLVHAS studies (7, 8
). Of particular concern are the observed excess prevalence of disability and lower rates of recovery among Hispanic females.
Conclusions
We have described patterns of functional dependence and mortality over a 22-month period as a step toward understanding ethnic differences and their effects on the community. Hispanic elderly experienced greater baseline levels of prevalent functional dependence than did their non-Hispanic White counterparts, but patterns of new dependence, recovery, and mortality did not increase the disparity. In particular, Hispanic elderly did not appear to be at increased risk of new dependence.
There are several plausible explanations for the results. The trends of the observed differences are in the expected directions, and the hypothesis may, in fact, be correct, but the study population may be too small or the duration of the study too short to identify significant ethnic differences. It is also possible that the single "independence" category may mask some relevant information about timing. Among those who reported "no disability" at baseline, a greater proportion of Hispanic than of non-Hispanic White respondents indicated "difficulty" with at least one activity at follow-up (crude ADL rates, 9.4 percent compared with 7.8 percent; crude IADL rates, 18.6 percent compared with 11.6 percent). Observation over a longer period might reveal that Hispanic elderly would acquire incident dependence at a greater rate than non-Hispanic White elderly if this reported increased incidence of difficulty were to evolve into dependence.
Culturally different interpretation of interview questions and resulting misclassification may have distorted the reported ethnic results. Zimmer et al. (26) suggested that daily living activity indicators may not adequately measure functional limitations cross-culturally because they reflect role expectations, norms, and living circumstances specific to particular (Western) societies and cultures. Johnson and Wolinsky (27
) proposed that racial differences in study outcomes may derive from the variable validity of scaled items between racial/ethnic groups. It is possible that culturally different interpretations of questions at baseline led to an overstatement of disparities, a difference in interpretation that decreased with repeated exposure to the interview-data collection experience. Transitions from dependence and independence to mortality were similar in both ethnic groups (table 2), which suggests that misclassification due to respondent interpretation or cultural norming is unlikely to be responsible for the patterns seen here.
The results more likely reflect a real decrease in or a stabilization of the disparity between prevalences of functional disability for Hispanics and non-Hispanic Whites over time. Greater prevalent disability in the Hispanic cohort, especially in women, may reflect a reservoir accumulated during younger years, possibly related to culture and socioeconomic status as well as to increasing age.
We have suggested several possible explanations for our results. Actual answers will require longer follow-up beginning at earlier ages, more sensitive indicators of disability, and exploration of cultural interpretations of relevant concepts.
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ACKNOWLEDGMENTS |
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NOTES |
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REFERENCES |
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