Statistical analysis
The sample size was calculated according to comparison of the primary endpoint of the MoCA‐BJ scores at 1 week after surgery on the basis of a pilot study (The Kolmogorov–Smirnov test was used to verify whether the data conforms to the normal distribution. Continuous data were expressed as the mean ± standard deviation. The Chi‐square or Fisher's exact test were used to analyse categorical data. Biochemical data were evaluated by Statistical analysis was performed using SPSS software (version 17.0).