Physical fitness and modifiable cardiovascular disease risk factors in survivors of childhood cancer: A report from the SURfit study

Background: Childhood cancer survivors are at risk for cardiovascular disease (CVD) because of intensive cancer therapies often accompanied by an unhealthy lifestyle. This study was aimed at 1) describing modifiable CVD risk factors in survivors and 2) investigating the association between different aspects of physical fitness and CVD risk factors. Methods: The authors analyzed cross-sectional data from ≥5-year survivors who were 16 years old or younger at their cancer diagnosis and 16 years old or older at the time of the study. Single CVD risk factors (waist circumference, blood pressure, fasting glucose, inverse high-density lipoprotein, and triglycerides), a composite CVD risk score (combined z scores of all CVD risk factors), and metabolic syndrome were evaluated. Physical fitness measures included cardiopulmonary exercise testing (CPET), a handgrip test, and a 1-minute sit-to-stand test (STS). Multivariable logistic regression was used for the association between fitness measures and CVD risk factors, with adjustments made for demographic factors and cancer therapy. Results: This study included 163 survivors with a median age at diagnosis of 7 years and a median age at the time of the study of 28 years. Among those survivors, 27% had a high waist circumference, 32% had high blood pressure, 19% had high triglycerides, 20% had an increased composite CVD risk score, and 10% had metabolic syndrome. A better performance during CPET, handgrip testing, and STS was associated with a lower probability of having a high waist circumference, high triglycerides, and metabolic syndrome. Conclusions: Better aerobic fitness (CPET) and, to a lesser extent, handgrip and STS were associated with fewer CVD risk factors. Further investigations are warranted to investigate which fitness measures should preferably be used to screen survivors to promote physical activity in those with impaired test performance. Lay summary: This study investigated the relationship between physical fitness of adult childhood cancer survivors and their risk factors for cardiovascular disease. Cardiovascular risk factors such as high blood pressure, a high waist circumference, and high blood lipids were frequently found in childhood cancer survivors. Survivors with better physical fitness (measured by a cycling test or simple strength and endurance tests) had a lower chance of having cardiovascular risk factors. This suggests that childhood cancer survivors could benefit from physical activity and general fitness by increasing their physical fitness and possibly decreasing their risk of cardiovascular disease. Keywords: cardiovascular disease; childhood cancer survivors; exercise test; metabolic syndrome; physical fitness