Proposal for a revised Barthel index classification based on mortality risk assessment in functional dependence for basic activities of daily living

Abstract

Introduction: Functional dependence on the performance of basic activities of daily living (ADLs) is associated with increased mortality. In this study, the Barthel index and its activities discriminate long-term mortality risk, and whether changes in this index are necessary to adapt it to detect mortality risk is examined.

Methods: Longitudinal study, carried out at the Orcasitas Health Center, Madrid (Spain), on the functional dependent population (Barthel ≤ 60). It included 127 people, with a mean age of 86 years (78.7% women and 21.3% men). Functional capacity was assessed using the Barthel index, and this index and each item it contains were analyzed as a test in relation to survival at three years, using tools that evaluate precision, discrimination, and calibration. The date of death was obtained from the health system.

Results: Greater dependency to perform chair-to-bed transfers was associated with an increased mortality risk (HR 2.957; CI 1.678-5.211). Also, individuals with severe (HR 0.492; CI 0.290-0.865) and moderate (HR 0.574; CI 0.355-0.927) ADL dependence had a reduced mortality risk when more independent in chair-to-bed transfers. Among people with moderate ADL dependence, this percentage was 48%. Using dependence-independence for chair-to-bed transfer as a screening test for mortality, the test showed high sensitivity (0.91) and specificity (0.83), a positive likelihood ratio of 5.45, and a negative likelihood ratio of 0.11. The area under the ROC curve was 0.814 (CI 0.658-0.970; p = 0.001), with a χ ² = 0.235; p = 0.889, according to the Hosmer-Lemeshow test. The concordance C index was 0.814. According to Nagelkerke's R², the model explained 53.1% of the variance in survival. As a screening test, "chair-to-bed transfer" was superior to the Barthel index.

Conclusion: ADL dependence for chair-to-bed transfers is an independent risk factor for mortality for any level of dependency. Therefore, a new classification of the Barthel index is proposed, in which "being dependent or requiring great assistance to perform chair-to-bed transfers" is considered severe dependence, even when the total score obtained via the Barthel Index is ≥40. We propose its use as a screening test in parallel to the Barthel index. The study suggests that the Barthel Index may have limitations in adequately discriminating mortality risk.

Keywords: Barthel index; basic activities of daily living; dependence; functional impairment; instrumental activities of daily living; mobility.

Figure 1

Flowchart of the process followed from the initial approach to carry out the study to the development of the fieldwork. Patient losses in the process and the cause of these losses are recorded.

Figure 2

Evaluation of the ability to discriminate mortality risk using the area under the ROC curve for the “chair-to-bed transfer” factor. The areas under the ROC curve of the Barthel index in its traditional and summary versions represent the dependency to perform basic activities of daily living of people who are dependent or independent to perform the “chair-to-bed transfer.”

Figure 3

Barthel index as a test to discriminate mortality. Areas under the ROC curve of the total (Barthel <20) and mild (Barthel 60) levels of the Barthel index in persons not dependent for chair-to-bed transfer. The area under the ROC curve of the variable “chair-bed dependence” represents exclusively persons who require great help to perform this activity, require minimal help, or are independent in its performance.

Figure 4

Areas under the ROC curve of the Barthel index estimated using the traditional four-level classification and the abbreviated two-level classification with respect to survival at 3 years. Comparison with the item “chair-to-bed transfer. Data for the whole cohort.

Figure 5

Cox regression analysis of the association between each level of dependency to perform “chair-to-bed transfers,” and survival at 3 years.

Figure 6

(A) Areas under the curve ROC of the Barthel index items and survival at 3-year follow-up among people with severe ADL dependence (Barthel less than 40). (B) Areas under the curve ROC of the Barthel index items and survival at 3-year follow-up among people with moderate ADL dependence (Barthel 40–60).

Figure 7

(A) ROC curve for the variables level of dependence and Barthel index item “chair-to-bed transfer” in people with ADL dependence and economic income less than 11,200 euros/year. (B) ROC curve for the variables’ level of dependence and Barthel index item “chair-to-bed transfer” in people with ADL dependence and economic income greater than 11,200 euros/year.