Statistical analysis

Continuous variables are presented as mean ± standard deviation (SD). Categorical variables are presented as frequencies and percentages. Student’s t-test was performed for the comparison of continuous variables and the χ²-test was used for categorical variables [12, 13]. Cancer incidence was determined by dividing the number of events by the number of person-years. The Cox proportional hazards model was used after stratifying for covariates, including age, sex, low income, smoking, alcohol consumption, diabetes, hypertension, dyslipidemia, and BMI. The results were presented as adjusted hazard ratios (aHR) with 95% confidence intervals (CI). All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC, USA) and R version 3.2.3 (The R Foundation for Statistical Computing, Vienna, Austria).