| Objectives:To explore whether there is a bidirectional causal relation between malnutrition and frailty in elderly COPD patients,and to analyze their combined effect on elderly COPD patients from the perspective of physical function.Methods:From December 2018 to March 2019,248 elderly hospitalized patients diagnosed with acute exacerbation of COPD were recruited from 7 hospitals in Beijing by convenient sampling method.During hospitalization(T1),Short-form Mini N utritional Assessment and Clinical Frailty Scale were used to access nutritional status and frailty,respectively.Physical function was measured by Activities of Daily Living Scale,including 6 Basic Daily Life Activities(BADL)and 8 Instrumental Daily Life Activities(IADL).S imultaneously,a self-designed questionnaire and other standardized scales were used for the assessment of sociodemographic characteristics,degree of dyspnea,co morbidities,cognitive function,anxiety and depression status.A follow-up were conducted at 6 months after discharge(T2),to collected data about nutritional status,frailty and physical function.Data analysis were conducted in SPSS22.0 software,including data description and univariate analysis such as t test,chi-square test and spearman correlation analysis.Binary Logistic regression was used to conduct cross-lag regression analysis and explore additive interaction of malnutrition and frailty,And the additive interaction coefficient was calculated in EXCEL2013 software,including the Relative Excess Risk due to Interact(RERI),the Attributable Proportion due to Interaction(AP)and the Synergy Index(S).Results:1.A total of 248 patients were investigated during hospitalization but 7 patients were excluded due to newly diagnosed cancer and 26 patients were discontinued due to unreachable or death during follow-up.Finally,215 patients completed the study.The prevelence of malnutrition and frailty were 49.3%and 47.4%,respectively.2.Correlation analysis showed that malnutrition was correlated with frailty(Tl:r 0.200,P=0.003;T2:r=0.327,P<0.001)significantly.In the cross-lag regression model after adjusting for social demographic factors,frailty of T1(OR=5.108,P=0.001)can significantly predict malnutrition of T2,and malnutrition of T1(OR=2.594.P=0.024)can also significantly predict frailty of T2.It indicated that there was a bidirectional causal relation between malnutrition and frailty.3.Comparision of the effects of malnutrition and frailty showed that,malnutrition had a significant effect on BADL impairment(P=0.021)and IADL impairment(P=0.045),without frailty included in the model.Frailty also had a significant effect on BADL impairment(P<0.001)and IADL impairment(P<0.001),without nutritional status included in the model When both malnutrition and frailty were included in the model,the effect of malnutrition on BADL impairment and IADL impairment was no longer significant(P>0.05),and the effect of frailty was attenuated but persistent(P<0.001):adjusted OR for BADL impairment and IADL impairment were 5.316and 13.687,respectively.4.The additive interaction analysis showed that,for those patients with only malnutrition or only frailty,the adjusted OR for BADL impairment was 1.116(P=0.869)and 3.913(P=0.023),respectively;however,for patients with malnutrition and frailty simultaneously,the adjusted OR for BADL impairment significantly increased to 7.820(P<0.001).For BADL impairment,RERI was 3.791(95%CI:0.826～6.756).AP was 0.495(95%CI:0.303～0.666),and S was 2.251(95%CI:1.487～3.407).Likewise,for those patients with only malnutrition or only frailty,the adjusted OR for IADL impairment was 1.369(P=0.520)and 11.046(P<0.001),respectively;however,for patients with malnutrition and frailty simultaneously,the adjusted OR for IADL impairment significantly increased to 23.652(P<0.001).For IADL impairment.RERI was 12.237(95%CI:0.903～23.571),AP was 0.517(95%CI:0.288～0.747),and S was2.175(95%CI:1.324～3.573).It indicated that there was a significant interaction of malnutrition and frailty on physical function of COPD patients,particularily,the interaction was synergistic.The combined effects of malnutrition and frailty on physical function were greater than the sum of each alone.Conclusion:1.There was a bidirectional causal relation between malnutrition and frailty in elderly COPD patients.2.Malnutrition and frailty had a synergistic effect on physical function of elderly COPD patients.Although malnutrition had no significant separated effect on physical function,when combined with frailty,it significantly increased the risk of function impairment.3.Frailty had a stronger effect on physical function of elderly COPD patients than malnutrition. |
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