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Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut.
Address correspondence to Thomas M. Gill, MD, Yale University School of Medicine, Dorothy Adler Geriatric Assessment Center, 20 York Street, New Haven, CT 06504. E-mail: thomas.gill{at}yale.edu
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Methods. We studied 754 community-living persons, 70 years old or older, who were nondisabled in four essential activities of daily living. Participants were followed with monthly telephone interviews for a median of 75 months to determine the occurrence of persistent (i.e., present for at least 2 consecutive months) disability in bathing and the time to the first long-term nursing home admission, defined as longer than 3 months.
Results. One hundred thirteen (15.0%) participants had a long-term nursing home admission. At least one episode of persistent bathing disability occurred among 59 (52.2%) participants with a long-term nursing home admission and 210 (32.8%) without a long-term admission (p <.001). In a proportional hazards model that was fully adjusted for potential confounders, the occurrence of persistent bathing disabilty increased the risk of a long-term nursing home admission by 77% (hazard ratio 1.77, 95% confidence interval 1.05 to 2.98), but had no effect on the risk of a short-term nursing home admission (hazard ratio 0.87, 95% confidence interval 0.51 to 1.49).
Conclusions. Among community-living older persons, the occurrence of persistent disability in bathing is independently associated with the risk of a long-term nursing home admission, but has no effect on short-term admissions. Interventions directed at the prevention and remediation of bathing disability have the potential to reduce the burden and expense of long-term care services.
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METHODS |
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The assembly of the cohort, which took place between March 1998 and October 1999, has been described in detail elsewhere (7). In brief, potential participants were identified from a computerized list of 3157 age-eligible members of a large health plan in greater New Haven, Connecticut. Eligibility was determined during a screening telephone interview and was confirmed during an in-home assessment. Persons who were physically frail, as denoted by a timed score of greater than 10 seconds on the rapid gait test (i.e., walk back and forth over a 10 ft [3 m] course as quickly as possible), were oversampled to ensure a sufficient number of participants at increased risk for disability (9). Only 4.6% of the 2753 health plan members who were alive and could be contacted refused to complete the screening telephone interview, and 75.2% of the eligible members agreed to participate in the project. Persons who refused to participate did not differ significantly in terms of age or sex from those who were enrolled. The study protocol was approved by the Yale Human Investigation Committee, and all participants provided verbal informed consent.
Data Collection
Comprehensive home-based assessments were completed by trained nurse researchers at baseline, 18, 36, and 54 months, whereas telephone assessments were completed monthly for a median of 75 months by a separate team of interviewers. All research staff were kept unaware of the study aims and hypotheses. Deaths were ascertained by review of the local obituaries and/or from an informant during a subsequent telephone interview; 232 (30.8%) participants died after a median follow-up of 44.5 months, and 32 (4.2%) dropped out of the study after a median follow-up of 23.0 months. Data were otherwise available for 98.6% of the 48,711 monthly telephone interviews.
Assessment of disability.-- Complete details regarding the assessment of disability, including formal tests of reliability and accuracy, are provided elsewhere (8). During the monthly telephone interviews, participants were assessed for disability using standard questions that were identical to those used during the screening telephone interview (8). For each of the four essential activities of daily living, we asked, "At the present time, do you need help from another person to (complete the task)?" Participants who needed help were considered to be disabled in the relevant task. Among a subgroup of 91 participants who were interviewed twice within a 2-day period by different interviewers, we found that the reliability of our disability assessment was substantial (10), with Kappa = 0.73 for disability in bathing and 0.71 for disability in one or more of the other three activities of daily living, hereafter referred to simply as nonbathing disability. To address the small amount of missing data on disability, we used multiple imputation with 50 random draws per missing observation according to the method described by Allison (11).
Assessment of covariates.-- During the comprehensive assessments, data were collected on a large array of covariates, which were subsequently grouped into four categories. The demographic factors included age, sex, race, education, and living situation (i.e., alone vs with others). The health-related factors included nine self-reported, physician-diagnosed chronic conditions; number of prescription medications; body mass index (BMI) based on self-reported height and weight; corrected near vision, assessed with a Jaeger card and calculated as the percentage of visual impairment (12); and hearing, as assessed with a handheld audioscope (13). The cognitive–psychosocial factors included cognitive status, as assessed by the Folstein Mini-Mental State Examination (MMSE) (14); depressive symptoms, as assessed by the Center for Epidemiologic Studies Depression (CES-D) Scale (15); functional self-efficacy, as assessed by the Tinetti Scale (16); and social support, as assessed by a modified version of the Medical Outcomes Study (MOS) Social Support Survey (17,18). Finally, the physical-functional factors included grip strength, as assessed by the average of three readings using a Jamar Hydraulic handheld dynamometer (Sammons Preston Rolyan, Bolingbrook, IL); and physical frailty, as previously defined. For all covariates, the amount of missing data was less than 1% in the baseline assessment and less than 5% in all subsequent assessments.
Assessment of outcome.-- Information on nursing home admissions was obtained during the monthly telephone interviews. Among a sample of 56 hospitalized participants, the reliability of this information, as compared with review of medical records, was almost perfect, with Kappa = 0.96. The primary outcome was time to the first long-term nursing home admission. Participants who were residents of a nursing home for four consecutive monthly interviews, corresponding to a minimal length of stay of 91 days, were classified as having a long-term admission. This choice corresponds to the criteria used previously by Tinetti and Williams (19). Admissions for short-term restorative or rehabilitative care after surgery or medical illnesses were excluded based on our underlying premise that persistent disability in bathing will lead to increased use of long-term care rather than subacute care. To explicitly test this premise, we evaluated short-term nursing home admissions (i.e., 3 months or less) as an outcome in a secondary set of analyses.
Statistical Analysis
The primary statistical method was proportional hazards analysis using time-dependent covariates (20). Data on participants without a long-term nursing home admission were censored at the time of death or the last completed interview prior to May 31, 2005.
The primary exposure was the occurrence of persistent (i.e., present for at least 2 consecutive months) disability in bathing, as assessed during the monthly telephone interviews. We chose to include episodes of persistent bathing disability as the primary exposure because they are more likely than are transient episodes (i.e., present for only a single month) to represent clinically meaningful changes in functional status (8).
To create a parsimonious model, we selected covariates according to a hierarchical screening process (21). First, we evaluated the bivariate association between each covariate at baseline and long-term nursing home admission (as a dichotomous outcome) using the chi-square test for categorical variables and t test for continuous variables. With the exception of age, sex, and race, which were retained for the final models, only covariates with a p value less than or equal to.30 were considered further. Next, we sequentially evaluated the correlations among the remaining covariates, first within each of the four previously described categories and then overall. When the Spearman's correlation coefficient was greater than 0.3, denoting potential collinearity, we chose a single covariate based on clinical judgment and the strength of association with the primary outcome. We then sequentially evaluated the impact of each of the remaining nine covariates on the overall model fit through a series of Cox proportional hazards models, which included persistent bathing disability, age, sex, and race. These covariates were updated, as indicated, using data from the subsequent comprehensive assessments. To assess each covariate's contribution to the model fit, we used a chi-square distribution with degrees of freedom equaling the number of parameters for the added covariate, based on the difference in the –2 Log Likelihood statistic (–2LL) between the models with and without the covariate. After fitting a separate model for each covariate, we added the covariate with the highest –2LL to the overall model. We continued this process iteratively until no covariate significantly increased the model fit based on the –2LL criterion. For the final model, we evaluated potential nonlinear effects of the selected continuous covariates, first by adding a quadratic term and then by categorizing these covariates using clinical cut points, and we assessed potential interactions between bathing disability and age, sex, and race, respectively. Finally, to account for other potential confounders, we reran our final model twice after sequentially adding two time-varying covariates—persistent nonbathing disability and acute hospitalization in the month prior to the nursing home admission (22), as ascertained from the monthly telephone interviews. The accuracy of these latter reports, based on an independent review of hospital records among a subgroup of 94 participants, was high, with Kappa = 0.94.
All statistical tests were two-tailed, and p <.05 was considered to indicate statistical significance. All analyses were performed using SAS (version 9.1; SAS Institute, Cary, NC).
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As shown in Table 1, several characteristics were significantly associated (p <.05) with a long-term nursing home admission in bivariate analyses. Hearing impairment did not meet the bivariate p value criterion (
.30) and was not considered further. Number of prescription medications, functional self-efficacy, and grip strength were highly correlated (p 
.30) with one or more of the other covariates and, hence, were also excluded from the multivariable analyses. At least one episode of persistent bathing disability occurred among 59 (52.2%) participants with a long-term nursing home admission and among 210 (32.8%) participants without a long-term admission (p <.001). The corresponding results for persistent nonbathing disability were 46 (40.7%) and 190 (29.6%), respectively (p =.019). Additional information on exposure to persistent bathing and nonbathing disability is provided in Table 2.
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DISCUSSION |
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From this observational study, we cannot establish a direct cause-and-effect relationship between persistent bathing disability and long-term nursing home admissions. Our methods and analyses were designed, however, to assess the evidence of an association in an unbiased manner. First, both bathing disability and nursing home admissions were ascertained prospectively by research staff who were unaware of the study aims and hypotheses. Second, the frequency of our assessments ensured that the occurrence of bathing disability preceded admission to the nursing home. Third, in our multivariable analysis we adjusted for a large number of demographic, health-related, cognitive, psychosocial, physical, and functional factors, including physical frailty, persistent disability in other activities of daily living, and acute hospitalization in the month prior to nursing home admission. Nonetheless, it is possible that additional unmeasured factors may have confounded the relationship between persistent bathing disability and long-term nursing home admissions. This possibility is diminished by our finding that persistent bathing disability was not independently associated with the risk of a short-term nursing home admission.
Our results are consistent with those of other investigators who have found, respectively, that needing personal assistance with bathing increased the odds of being admitted to a nursing home or receiving paid, long-term home services nearly 5-fold over a 1-year period (5) and that bathing was the most important activity of daily living in predicting paid and unpaid hours of personal assistance (6). While providing evidence to support the deleterious effects of bathing disability, these prior studies accounted for only a limited array of factors that confer high risk for adverse outcomes among older persons. We conducted the current study because it was uncertain whether bathing disability is an independent risk factor for long-term nursing home admissions.
Our study was not designed to establish the mechanisms by which bathing disability leads to long-term nursing home admissions. Two possible bathing-related pathways include: (i) inadequate availability of personal assistance in the home and (ii) safety concerns. As noted earlier, relative to other activities of daily living, bathing requires the highest number of paid and unpaid hours of care (6). From a safety perspective, a disproportionate number of injurious falls occur in the bathroom (24,25). Moreover, in an earlier clinical trial (26), we found that many frail older persons were fearful of falling while bathing. Rates as high as 30% have been reported in other studies of community-living older persons (25). In addition, about one in seven older persons who experience difficulty getting out of their bathtub have been stuck in the tub on at least one occasion (27). These bathing-related problems adversely affect the quality of life of community-living older persons and may inform the decision-making process regarding the need for long-term nursing home admissions.
Whether our findings can be generalized widely may be reasonably questioned. As previously noted (22), the demographic characteristics of our source population closely mirror those of persons 70 years old or older in New Haven County, which, in turn, are comparable to those in the United States as a whole. The high participation rate, completeness of data collection, and low rate of attrition for reasons other than death all enhance the generalizability of our findings (28), and at least partially offset the absence of a population-based sample.
The prevalence of bathing disability increases substantially with age, such that 21% of community-living persons 85 years old or older require personal assistance for bathing (29). The results of the current study, coupled with earlier findings (5,6,30), indicate that disability in bathing likely contributes to costly long-term care services. Interventions directed at the prevention and remediation of bathing disability, therefore, have the potential to reduce the burden and expense of long-term care services. Identifying potentially modifiable risk factors for bathing disability, including the absence or nonuse of adaptive equipment, should be a high research priority.
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We thank Denise Shepard, BSN, MBA, Shirley Hannan, RN, Andrea Benjamin, BSN, Martha Oravetz, RN, Alice Kossack, Barbara Foster, Shari Lani, Alice Van Wie, and the late Bernice Hebert, RN for assistance with data collection; Evelyne Gahbauer, MD, MPH for data management and programming; Wanda Carr and Geraldine Hawthorne for assistance with data entry and management; Peter Charpentier, MPH for development of the participant tracking system; and Joanne McGloin, MDiv, MBA, for leadership and advice as the Project Director.
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Received December 20, 2005
Accepted March 13, 2006
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This article has been cited by other articles:
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  J. K. Johnson, L.-Y. Lui, and K. Yaffe Executive Function, More Than Global Cognition, Predicts Functional Decline and Mortality in Elderly Women J. Gerontol. A Biol. Sci. Med. Sci., October 1, 2007; 62(10): 1134 - 1141. [Abstract] [Full Text] [PDF]
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L. Coll-Planas, T. Nikolaus, and E. P. Loayza WHAT CAN IT BE AND WHAT WAS IT REALLY? ABOUT BATHING AND URINARY INCONTINENCE LEADING TO NURSING HOME ADMISSION J. Gerontol. A Biol. Sci. Med. Sci., June 1, 2007; 62(6): 681 - 681. [Full Text] [PDF]
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R. L. Kane Response to Letter from Coll-Planas and Colleagues on Bathing and Urinary Incontinence Leading to Nursing Home admission J. Gerontol. A Biol. Sci. Med. Sci., June 1, 2007; 62(6): 682 - 682. [Full Text] [PDF]
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R. L. Kane Ptolemaic bathing. J. Gerontol. A Biol. Sci. Med. Sci., August 1, 2006; 61(8): 819 - 820. [Full Text] [PDF]
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