Difficulty and Dependence: Two Components of the Disability Continuum among Community-Living Older Persons

Assessing disability in basic activities of daily living (BADLs) has become increasingly important in both patient care and clinical research as the population of older persons with multiple chronic diseases and infirmities grows. Basic activities of daily living typically include the personal care tasks, such as bathing, dressing, and using the toilet, that are considered essential for independent living [1]. A consensus may exist about which BADLs to include in a disability assessment, but there is less agreement about how BADL disability should actually be assessed [2]. Most epidemiologic studies have defined BADL disability as dependence, that is, requir[ing] help from another person [3]. Some investigators, however, have argued that BADL disability should be defined as degree of difficulty [4]. This disagreement about a key measurement issue in geriatric assessment prompted us to ask whether the current practice of defining BADL disability as either difficulty or dependence might represent a false choice. We sought to determine whether questions about difficulty and dependence provide complementary information. We hypothesized that persons who are independent in BADLs but have difficulty would have functional profiles, physical performance scores, and rates of health care utilization and death that are between those of persons who are BADL independent and have no difficulty and persons who are BADL dependent. If this hypothesis is correct, it would suggest that clinicians and investigators could depict the continuum of disability more fully by including questions about both difficulty and dependence in their clinical practice or epidemiologic studies. Methods Participants Participants were members of Project Safety, a probability sample of community-living persons 72 years of age and older in New Haven, Connecticut, in 1989. The sampling technique, described in detail elsewhere [5], was similar to that used to establish the New Haven site of the Established Populations for Epidemiologic Studies of the Elderly [6]. Of the 1436 persons originally contacted, only 44 (3%) did not meet the three eligibility criteria: the ability to speak English, Spanish, or Italian; the ability to follow simple commands; and the ability to walk across a room without the assistance of another person. Of those eligible, 1103 (79%) agreed to participate and were enrolled in the cohort. The sample for the current study comprised the 1065 participants who had complete baseline data on BADL function. The 38 persons who had incomplete BADL data did not differ significantly from those in our study sample in terms of mean age (81.2 years compared with 79.5 years), sex (76.3% female compared with 72.8% female), or ethnicity (81.6% white compared with 84.0% white). Data Collection Baseline interviews and assessments were completed in participants' homes by a trained nurse researcher. To assess BADL function, participants were asked two separate questions for each of six personal care tasks: bathing, dressing, transferring from bed to chair, eating, using the toilet, and grooming [1, 7]. Participants were first asked, At the present time, do you need help (yes/no) from another person to (perform the task)? They were then asked, How much difficulty (none, some, a lot), on average, do you have doing this [task]? Measures of higher-level function included 1) four instrumental activities of daily living (performing light and heavy housework, shopping, and driving a car) derived from the Older American Resource Services instrument [8]; 2) mobility, determined from the number of blocks walked on an average day; 3) physical activity, assessed with a modified version of the Yale Physical Activity Scale [9]; and 4) social activity, scored as the sum of the frequency ratings of eight groups of activities (attending events, taking trips, engaging in paid work, volunteering, visiting friends, attending religious services, participating in groups, and going to museums or shows) [10]. Physical performance was assessed with three timed tests that previous investigations [11, 12] found to be most predictive of BADL dependence at 1 year. The tests included walking back and forth over a 10-foot course, turning in a full circle, and standing up and sitting down from a hard-back chair three times with arms folded. The time (in seconds) needed to complete each task as quickly as possible was recorded. During follow-up interviews at 1 and 3 years, BADL function was reassessed and participants were asked, Do any health-care workers visit you in your home on a regular basis to take care of you (yes/no)? The remaining outcomes were monitored over a 4-year period. Hospitalizations were ascertained from monthly surveillance of discharge records at two local hospitals, which account for more than 90% of acute care admissions for persons living in New Haven, and from Health Care Financing Administration (HCFA) data tapes, which include admissions to hospitals within and outside of New Haven. Admissions to skilled-nursing facilities were ascertained from the Connecticut Long Term Care Registry [13]. Mortality was monitored by contacts with participants or their proxies during monthly surveillance and by review of local obituaries [5]. Statistical Analysis For our primary analysis, we classified participants into one of three BADL groups: 1) independent without difficulty if they required no personal assistance and reported no difficulty in any BADL [n = 701]; 2) independent with difficulty if they required no personal assistance in any BADL but reported some or a lot of difficulty in one or more BADLs [n = 227]; and 3) dependent if they required personal assistance in one or more BADLs (n = 137). To test our hypothesis, we did a series of cross-sectional and longitudinal analyses. In the cross-sectional analysis, we first compared the proportion of participants in the three BADL groups who had poor higher-level function. Measures of poor higher-level function included dependence in one or more instrumental activities of daily living, no blocks walked on an average day, worst quarter of physical activity, and worst quarter of social activity. Next, for each of the timed tests of physical performance, we dichotomized the scores to distinguish participants in the worst quarter from those in the other three quarters [11, 12], and we compared the proportion of participants in the three BADL groups who scored in the worst quarter. In the longitudinal analysis, we first compared the rates of hospitalization and regular visits by a home health care worker among the three BADL groups. We then calculated survival curves for admission to a skilled-nursing facility and for death using the product-limit method of Kaplan and Meier [14]. In both survival analyses, participants were censored at the end of the monthly surveillance (31 August 1993) if an outcome had not occurred. When the outcome was admission to a skilled-nursing facility, decedents without a previous admission to a skilled-nursing facility were censored at the time of death. Differences in survival curves were assessed by using the log-rank test statistic [15]. The Mantel-Haenszel chi-square statistic for linear trend was used for all other statistical comparisons among the three BADL groups. Finally, among participants who were BADL independent at baseline, we compared the rate of new BADL dependence over a 3-year period between those who had difficulty and those who did not. For all rates and proportions, we calculated 95% CIs. To determine whether the postulated association between difficulty and dependence was seen for individual BADLs, we did a secondary set of analyses. Bathing was evaluated because it is generally the BADL with the highest prevalence of disability [11]. We classified participants into one of three bathing groups-independent with no difficulty (n = 812), independent with difficulty (n = 139), and dependent (n = 114)-and repeated the cross-sectional and longitudinal analyses described previously. Results The number and type of BADL disabilities among participants who were BADL independent with difficulty and those who were BADL dependent are shown in Table 1. Most participants in each group had only one or two BADL disabilities; disability was most common in bathing and dressing. Table 1. Number and Type of Disabilities in Basic Activities of Daily Living In the cross-sectional analysis, the proportion of participants who had poor higher-level function was lowest in those who were BADL independent without difficulty, intermediate in those who were BADL independent with difficulty, and highest in those who were BADL dependent (chi-square trend, P < 0.001). This finding was seen for each self-reported measure (Table 2, top). The results for physical performance were similar (Table 2, middle). For each of the timed tests, the proportion of participants in the quarter with the worst function increased across the three BADL groups (chi-square trend, P < 0.001). With only two exceptions, the 95% CIs for pair-wise comparisons between BADL groups in the cross-sectional analysis did not overlap; this provides even stronger evidence for the graded association among the three BADL groups. Table 2. Higher-Level Function, Physical Performance, and Health-Related Outcomes in the Three Basic Activities of Daily Living Groups* In the longitudinal analysis, rates of hospitalization and regular visits by a home health care worker for participants who were BADL independent with difficulty were intermediate compared with corresponding rates for the other two groups (Table 2, bottom). Among persons who were BADL independent, those with difficulty were significantly more likely to develop BADL dependence over a 3-year period than those without difficulty (relative risk, 1.7 [95% CI, 1.3 to 2.2]). The cumulative probability of admission to a skilled-nursing facility increased steadily for all three BADL groups (Figu