Prospectively measured lifestyle factors and BMI explain differences in health-related quality of life between colorectal cancer patients with and without comorbid diabetes

PURPOSE: This study aimed to assess the longitudinal association between lifestyle factors, body mass index (BMI), and health-related quality of life (HRQoL) among colorectal cancer patients with (CRCDM+) and without diabetes (CRCDM−). METHODS: Data from a longitudinal study among CRC patients diagnosed between 2000 and 2009 were used. Clinical characteristics were retrieved from the Netherlands Cancer Registry and questionnaires were sent in 2010, 2011, and 2012 using the Patient Reported Outcomes Following Initial Treatment and Long term Evaluation of Survivorship (PROFILES) registry. Lifestyle (including moderate-to-vigorous physical activity (MVPA), smoking and alcohol use), BMI, diabetes status, and HRQoL were assessed in the questionnaire. RESULTS: One thousand seven hundred thirty-nine (49 %) patients responded to ≥2 questionnaires, of whom 126 CRCDM+ and 789 CRCDM− patients were included. CRCDM+ patients had a higher BMI (29.1 ± 4.2 vs. 26.4 ± 3.7 kg/m(2)), whereas the number of alcohol users was lower (50 vs. 70 %, p value <0.0001) among CRCDM+ as compared to CRCDM− patients. Analyses adjusted for sociodemographic and cancer characteristics showed that CRCDM+ patients reported statistically significantly lower physical function (beta = -5.76; SE = 1.67), global QoL (beta = -4.31; SE = 1.48), and more symptoms of fatigue (beta = 5.38; SE = 1.95) than CRCDM− patients. However, these effects disappeared after adjustments for lifestyle factors and BMI which were all significant predictors of HRQoL. Additional adjustment for comorbidity further attenuated the main effect of DM on HRQoL. CONCLUSIONS: Diabetes was not independently associated with HRQoL but deteriorated HRQoL among CRCDM+ patients seem to be explained by an unhealthier lifestyle and other comorbid conditions. Moreover, residual confounding cannot be ruled out.