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. 2021 Mar 27;13(4):1098.
doi: 10.3390/nu13041098.

Identification of Mortality Risks in the Advancement of Old Age: Application of Proportional Hazard Models Based on the Stepwise Variable Selection and the Bayesian Model Averaging Approach

Ewelina Łukaszyk  1   2 , Katarzyna Bień-Barkowska  3 , Barbara Bień  1   2
Affiliations

Identification of Mortality Risks in the Advancement of Old Age: Application of Proportional Hazard Models Based on the Stepwise Variable Selection and the Bayesian Model Averaging Approach

Ewelina Łukaszyk et al. Nutrients. .

Abstract

Identifying factors that affect mortality requires a robust statistical approach. This study's objective is to assess an optimal set of variables that are independently associated with the mortality risk of 433 older comorbid adults that have been discharged from the geriatric ward. We used both the stepwise backward variable selection and the iterative Bayesian model averaging (BMA) approaches to the Cox proportional hazards models. Potential predictors of the mortality rate were based on a broad range of clinical data; functional and laboratory tests, including geriatric nutritional risk index (GNRI); lymphocyte count; vitamin D, and the age-weighted Charlson comorbidity index. The results of the multivariable analysis identified seven explanatory variables that are independently associated with the length of survival. The mortality rate was higher in males than in females; it increased with the comorbidity level and C-reactive proteins plasma level but was negatively affected by a person's mobility, GNRI and lymphocyte count, as well as the vitamin D plasma level.

Keywords: Bayesian model averaging; Charlson Comorbidity Index; GNRI; TUG; geriatrics; lymphocytes; survival; vitamin D.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; and in the decision to publish the results.

Figures

Figure 1
Figure 1
Association between the sociodemographic and health-related characteristics of former geriatric patients and their mortality rate: Results from the univariable Cox PH model (panel A) and the multivariable Cox PH model obtained with the stepwise backward variable selection method with the significance level set as p < 0.05 (panel B).
Figure 2
Figure 2
Survival curves for a geriatric patient depending on his or her sex and the selected health-related covariates identified using the stepwise backward variable selection approach (with p < 0.05): Age-weighted Charlson Comorbidity Index (panel A), the speed of performing the Timed Up and Go (TUG) test (panel B), total lymphocyte count (panel C), Geriatric Nutritional Risk Index (panel D), the vitamin D level (panel E), and CRP level (panel F). For each panel, the survival curves were derived from the multivariable Cox PH model for given sex and for selected very low or very high values of one explanatory variable, whereas the values of remaining covariates in the model were set at their average level.
Figure 3
Figure 3
Classification of geriatric patients into the category of lower mortality risk and the category of higher mortality risk based on seven most important predictors identified by both: The stepwise backward selection method and the iterative BMA approach. Results from the 10-fold cross-validation of the multivariable Cox PH model.
Figure 4
Figure 4
Kaplan–Meier survival curves for patients assigned to a higher and a lower mortality risk category based on a 10-fold cross-validation. Results of the multivariable Cox PH model with the same seven most important risk factors for mortality rate identified by both: The stepwise backward variable selection and the iterative BMA approach.
See this image and copyright information in PMC

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