Low cardiorespiratory fitness and physical functional capacity in obese patients with schizophrenia

Abstract

Background: Low cardiorespiratory fitness is a prominent behavioral risk factor for cardiovascular disease (CVD) morbidity and mortality, as cardiorespiratory fitness is strongly associated with CVD outcomes. High rates of CVD have been observed in the schizophrenia population, translating into a markedly reduced life expectancy as compared to healthy controls. Surprisingly however, while cardiorespiratory fitness is an eminent indicator for overall cardiovascular health as well as eminently modifiable risk factor for CVD, no studies have systematically assessed cardiorespiratory fitness in schizophrenia.

Methods: Community-dwelling schizophrenia patients underwent graded-exercise tests, to ascertain maximal oxygen uptake (Max Vo2), considered to be the gold standard for the evaluation of cardiorespiratory fitness and physical functional capacity. The modified Bruce protocol was used to ascertain cardiorespiratory fitness and physical functional capacity; data was normalized and compared to population standards derived from the ACLS (Aerobics Center Longitudinal Study) and the National Health and Nutrition Examination Surveys (NHANES), Cycles III and IV.

Results: Data for n=117 participants (41% male, 46% white) was analyzed. Mean age (y) was 43.2±9.9, and mean BMI was 37.2±7.3. Peak HR attained during exercise was 145.6±19.6, after 8.05±3.6 min, achieving 111.2±44.2W. Max Vo2 was 1.72±6.6l/min, MaxVCo2 1.85±7.2l/min, and minute ventilation (VE) was 55.6±21.9 ml/s. PANSS Positive subscores (13.3±4.4; r=-0.21, p=0.024) were inversely correlated with Max Vo2 ml(-1)min(-1) kg(-1). Neither PANSS Total (56.3±12.3; r=-0.105, p=0.72), PANSS Negative (14±5.1; r=-0.52, p=0.57) nor PANSS General Psychopathology (28.4±7.4; r=-0.28, p=0.76) scores were correlated with Max Vo2 ml(-1) min(-1) kg(-1). Peak heart rate and duration of exercise were not correlated with PANSS scores. Compared to healthy controls derived from the ACLS and NHANES, respectively, 115 participants achieved 'low levels' of fitness only, as well as highly significantly reduced Max Vo2, across all age groups.

Conclusion: The test was generally well received and tolerated by those who elected to participate; and adherence to the protocol was good. Among participants with schizophrenia, most of whom were obese, and across all age groups, cardiorespiratory fitness was exceedingly poor. Only two participants in our entire sample fit the categorization of 'moderate fitness level'; that is, a fitness level at or above the 20th percentile of ACLS-derived population comparisons. Conversely, this left 98.3% of participants with schizophrenia below population standards. Low cardiorespiratory fitness emerges as an eminent modifiable risk factor for CVD mortality and morbidity in schizophrenia complicated by obesity.