The Effects of Age, Physical Inactivity and Fatigue on Handgrip Strength Related Upper Extremity Functionality in Patients With Breast Cancer: a Mediation Analysis

Abstract Purpose: This study was aimed to assess the effect of age, fatigue, self-reported function, and physical inactivity on handgrip strength related upper extremity function (HGSf) in breast cancer survivors (BCS). Secondarily, the potential mediator effects of fatigue and physical inactivity were also studied. This study was registered to Clinical Trials: NCT04245657.Methods: 111 female BCS (Mean age and BMI: 51.20±9.33 year and 27.86±3.70 kg/m2, respectively) were included in this study. Handgrip strength (HGS) was assessed with dynamometer while fatigue, self-reported upper extremity function and physical inactivity as sitting time were assessed with Fatigue Severity Scale (FSS), Disabilities of Arm, Shoulder and Hand Questionnaire (DASH), and 7th question of International Physical Activity Questionnaire Short Form, respectively. Results: HGS was found significantly higher on the right side compared to the left side (22.63±3.50 kgF vs 21.30±3.65 kgF, t=5.083, p<0.001). The mean sitting time, DASH and FSS were found 5.7 hours, 22.67 and 39.55, respectively. The multivariate linear regression analysis showed a total of 28% of the cumulative variance in HGSf is explained by age, DASH and sitting time variables (F (3,107) =12.057, p<0.001, R2=0.280). Fatigue was not found as a mediator in the hypothesized structural equation model while sitting time had a significant mediator effect between the age and HGSf (β=-0.004 (95% CI-0.075/-0.004), p=0.019)Conclusions: Increased physical inactivity and age play a major role in strength-related upper extremity function in BCS. Patient-specific physiotherapy programs should also consider this especially in older and physically BC patients in rehabilitation and long-term care.