Differences in the Relationships Between Muscle Strength, Muscle Mass, Balance Function, and Quality of Life for Middle-Aged and Older Breast Cancer Survivors

Purpose: The purpose of this study was to investigate the differences in muscle strength, muscle mass, balance function, and quality of life (QOL) among middle-aged breast cancer survivors (BCSs) and older BCSs. Methods: The study included 53 middle-aged (<65 years old) BCSs and 49 older (≥65 years old) BCSs. Muscle strength was evaluated via handgrip and knee extensor strength, and muscle mass was assessed using a body composition test. Balance function was assessed using the Timed Up and Go test and the body sway test. QOL was assessed using the Medical Outcome Study 36-item Short-Form Health Survey. Results: The older BCSs had significantly lower right grip strength, right knee extension strength, and muscle mass (P <.05) than the middle-aged BCSs. In addition, the body sway test showed that older BCSs had a significant increase in the length of center of pressure compared to middle-aged BCSs (P <.05). Older BCSs showed significantly lower physical functioning subscales in QOL compared to middle-aged BCSs (P <.05). The associations among muscle strength, muscle mass and QOL were more significantly observed in the older BCSs (P <.05). Furthermore, a significant correlation between QOL and balance function was observed in the older BCSs, but not in the middle-aged BCSs (P <.05). Conclusion: There may be associations among muscle strength, muscle mass, balance and QOL in older BCSs, but not in middle-aged BCSs. We believe that the findings of this study will be relevant in the context of planning rehabilitation for older BCSs.