Association of Admission Functional Status and Body Mass Index with Mortality in Patients Receiving Chronic Dialysis: A Nationwide Observational Cohort Study

Abstract

Introduction: Chronic kidney disease (CKD) significantly affects activities of daily living (ADLs) before and after the initiation of dialysis, particularly in elderly individuals. However, the impact of admission functional status on dialysis patients' outcome is not fully understood. This study aimed to investigate the effect of the number of ADL disabilities usually measured for all patients hospitalized in Japan on in-hospital outcome for dialysis patients.

Methods: Using an inpatient administrative claims database, we included 104,557 admissions of patients undergoing chronic dialysis aged 65 years and above from 2012 to 2014. The primary outcome was in-hospital all-cause mortality (evaluated using logistic regression models), and the secondary outcomes were length of stay and care cost.

Results: The mean age of the participants was 74.0 ± 6.2 years, the mean body mass index (BMI) was 21.8 ± 3.9, 31% needed assistance for one or more of five basic ADLs (feeding, transferring, going to toilet, dressing, and bathing) at admission, and 3.5% (n = 3,701) died after hospitalization. After adjusting for confounding factors, the odds ratios (ORs) (95% confidence intervals) of death for 1, 2, 3, 4, and 5 ADL disabilities were 1.43 (1.19-1.70), 2.04 (1.71-2.45), 2.58 (2.19-3.04), 3.74 (3.35-4.17), and 6.83 (6.29-7.41) versus a complete independence, respectively. The increasing number of ADL disabilities was also associated with greater length of stay and costs. Risk stratification by age, admission functional status, and BMI showed an 18-mortality risk matrix with a maximal risk of a 15.5-higher OR for lean patients aged ≥75 years with severe ADL disability compared with that for patients aged <75 years with middle BMI and no ADL disability on admission.

Conclusions: Admission functional status decline significantly increases in-hospital mortality, length of stay, and costs. Routine assessment of functional status can facilitate the risk prediction of dialysis patients.

Keywords: activity of daily living; age; body mass index; chronic kidney disease; dialysis; functional status.

Figure 1.

Rates of dependence of basic ADLs at admission according to the reasons for admission among maintenance dialysis patients. a, The diagnostic causes of hospitalization were stratified into the 12 categories shown based on the International Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). b, Proportion of each number that required assistance for the five basic ADLs (feeding, transferring, toileting, dressing, and bathing) according to the diagnostic causes of hospitalization in end-stage kidney disease.

Figure 2.

Odds ratios for in-hospital mortality according to the reason for admission in dialysis patients with ADL disability versus no disability. Models were adjusted for age, sex, body mass index, dialysis modality, and Charlson Comorbidity Index. Each box represents a point estimate of OR, and the solid lines represent the corresponding 95% CI. ADL, activities of daily living; CI, confidence interval; OR, odds ratio.

Figure 3.

A risk matrix for in-hospital mortality according to admission functional status, age, and BMI categories. The odds ratio with 95% CI and numbers of events and individuals are described for each category. Models were adjusted for sex, dialysis modality, and Charlson Comorbidity Index. ADL, activities of daily living, BMI, body mass index.