Does higher cardiorespiratory fitness impact the clinical symptoms in individuals with schizophrenia? A tertiary analysis of the CORTEX-SP study

Abstract

Problem statement and purpose: Cardiorespiratory fitness (CRF) is recognized as a modifiable risk factor that can help reduce the risk of non-communicable diseases, and as such, it serves as a crucial reference for vital signs. Moreover, it has been found to have a negative association with clinical symptoms. Nevertheless, the specific impact of each variable on the clinical symptoms of schizophrenia (SP) remains unclear. Therefore, the objective of this study was to examine the predictive significance of CRF and body composition concerning clinical symptom factors in the population with SP. Approach: Body composition, specifically body mass index (BMI), and CRF, measured as peak oxygen uptake from the cardiopulmonary exercise test, were evaluated in all participants (n = 122, 41.6 ± 10.3 years old, 16.7% women). The psychopathology of the participants was assessed using the Brief Negative Symptom Scale and the Positive and Negative Syndrome Scale. Correlations, including Spearman's Rho and Pearson's r, were conducted to examine the relationships between sociodemographic factors, symptoms, and BMI. Stepwise Multiple Regression analyses were then employed to identify the variables that can predict CRF. Results: The correlations revealed a negative association between negative symptoms and peak oxygen uptake (mL·kg−1·min−1) (B = −0.252; P < 0.001). The regression analysis showed that lower peak oxygen uptake (L·min−1) (P < 0.001) and higher BMI (P = 0.019) were predictors of negative symptoms, explaining 22.8% of the variance (R2 = 22.8%; F = 8.067; P < 0.001). Additionally, lower peak oxygen uptake (mL·kg−1·min−1) (P = 0.016) predicted general symptoms (R2 = 12.3%; F = 5.135; P = 0.002), and lower peak oxygen uptake (mL·kg−1·min−1) (P = 0.001) predicted total symptoms (R2 = 17.8%; F = 7.928; P < 0.001). Conclusions: Given the significant associations observed between CRF and BMI with negative symptoms, and CRF with general and total symptoms, it becomes evident that enhancing physical health through exercise and adopting a healthy diet may serve as crucial adjunctive treatments for managing SP disorder.