Association of preoperative nutritional status evaluated by the controlling nutritional status score with walking independence at 180 days postoperatively: a prospective cohort study in Chinese older patients with hip fracture

Abstract

Background: Malnutrition is significantly associated with unfavorable outcomes, but there is little high-level evidence to elucidate the association of malnutrition with losing walking independence (LWI) after hip fracture surgery. This study aimed to assess the association between preoperative nutritional status evaluated by the Controlling Nutritional Status (CONUT) score and walking independence at 180 days postoperatively in Chinese older hip fracture patients.

Methods: This prospective cohort study included 1958 eligible cases from the SSIOS database. The restricted cubic spline was used to assess the dose-effect relationship between the CONUT score and the recovery of walking independence. Propensity score matching was performed to balance potential preoperative confounders, and multivariate logistic regression analysis was applied to assess the association between malnutrition and LWI with perioperative factors for further adjustment. Furthermore, inverse probability treatment weighting and sensitivity analyses were performed to test the robustness of the results and the Fine and Gray hazard model was applied to adjust the competing risk of death. Subgroup analyses were used to determine potential population heterogeneity.

Results: The authors found a negative relationship between the preoperative CONUT score and recovery of walking independence at 180 days postoperatively, and that moderate-to-severe malnutrition evaluated by the CONUT score was independently associated with a 1.42-fold (95% CI, 1.12-1.80; P =0.004) increased risk of LWI. The results were overall robust. And in the Fine and Gray hazard model, the result was still statistically significant despite the apparent decrease in the risk estimate from 1.42 to 1.21. Furthermore, significant heterogeneities were observed in the subgroups of age, BMI, American Society of Anesthesiologists score, Charlson's comorbidity index, and surgical delay ( P for interaction < 0.05).

Conclusion: Preoperative malnutrition is a significant risk factor for LWI after hip fracture surgery, and nutrition screening on admission would generate potential health benefits.

Figure 1

Flowchart for selection of study subjects. CONUT, controlling nutritional status; PSM, propensity score matching.

Figure 2

Dose-effect relationship between the CONUT score and recovery of walking independence among Chinese older patients with hip fracture¹. Evaluated by using a restricted cubic spline model with four knots and adjusted by all preoperative covariables with P-value < 0.1, including age, fracture type, American society of anesthesiologists (ASA) score, Charlson’s comorbidity index (CCI), marital status, occupation, surgical delay, the CONUT score, hypertension, diabetes, cerebrovascular disease, heart disease, pneumonia, surgical history, current smoking, operation type, and surgical duration. P-nonlinearity showed no statistical significance, which was estimated using the likelihood ratio test comparing the restricted cubic spline model with the linear model. Relative risks were indicated by red solid line and 95% CIs by red shaded area, in which the reference point was 5 for the CONUT score. Blue shaded area showed the frequency distribution of CONUT scores. CONUT, controlling nutritional status.

Figure 3

SMDs distribution of preoperative covariables and their changes before and after PSM. SMD < 0.1 indicated adequate between-group balance. ASA, American society of anesthesiologists; CCI, Charlson’s comorbidity index; COPD, chronic obstructive pulmonary disease; PSM, propensity score match; SMD, standardized mean difference.

Figure 4

The association of HCS with the risk of LWI in various subgroups. RRs of LWI in relation to HCS were calculated using multivariable logistic regression models, which were adjusted by operation type, anesthesia type, surgical duration and perioperative blood transfusion. P for interaction were calculated using likelihood ratio tests. ASA, American society of anesthesiologists; CI, confidence interval; CCI, Charlson’s comorbidity index; CONUT, controlling nutritional status; HCS, high CONUT score; LWI, losing walking independence; LCS, low CONUT score; RR, relative risk.