Investigation of Exercise Capacity, Pulmonary Function, Respiratory Muscle Strength, and Quality of Life in Patients Diagnosed With Schizophrenia and Bipolar Disorder

Schizophrenia is a mental disorder observed in approximately 4 out of every 1,000 individuals in the general population, with a morbidity rate of 0.72%. According to the Global Burden of Disease Study (2010), around 20,000 deaths occur annually due to schizophrenia-related causes. Bipolar disorder is recognized as a chronic and severe mental illness. Based on data from the World Health Organization's global burden of disease reports, bipolar disorder ranks among the top 20 diseases contributing to disability worldwide and holds the 6th position among mental disorders.

Schizophrenia and bipolar disorder are serious and chronic psychiatric conditions affecting millions of individuals globally. The prevalence of schizophrenia is approximately 1%, while bipolar disorder has a lifetime prevalence of 2-3%. These disorders not only involve neuropsychiatric symptoms but also significantly impact physical health. In individuals with these conditions, sedentary lifestyle habits, metabolic side effects of antipsychotic and mood-stabilizing medications, and increased comorbidity risks are associated with notable reductions in exercise capacity.

Moreover, physical inactivity and heightened inflammatory processes may adversely affect respiratory muscle strength and pulmonary function. Studies have shown that patients with schizophrenia exhibit significantly lower maximal oxygen consumption (VO₂max) and anaerobic threshold levels compared to healthy individuals. In bipolar disorder, depressive episodes are marked by reduced exercise capacity, while manic episodes often involve irregular and risky physical activities.

Additionally, both disorders are associated with significantly lower pulmonary function parameters (FVC, FEV₁) compared to the healthy population. Respiratory muscle strength, a relatively underexplored area, is gaining importance. In schizophrenia cases dominated by negative symptoms, reduced inspiratory muscle strength combined with insufficient physical activity can severely limit patients' quality of life and independence. Similarly, in bipolar disorder, impairments in pulmonary capacity and respiratory muscle strength negatively affect quality of life.

Quality of life in these individuals is closely linked not only to mental health but also to physical capacity and pulmonary function. Enhancing respiratory muscle strength and aerobic capacity may positively influence overall quality of life, social participation, and functional status. However, the existing literature remains limited and fragmented. There is a noticeable lack of studies that simultaneously evaluate exercise capacity, pulmonary function, and respiratory muscle strength in individuals with psychiatric disorders.