Statistical analysis
Categorical variables are shown as percentages and continuous variables
as medians with interquartile range (25th and 75th percentiles) due to
the distribution. Distribution relationship between categorical
variables values was tested using χ2-test, and if necessary, Fisher’s
exact test. To analyze the difference between three continuous variables
Kruskal-Wallis test with post hoc Mann-Whitney U-test for non-parametric
analysis was used, while the difference between two continuous variables
was tested using Mann-Whitney U-test. Multivariable logistical
regression analyses were conducted to identify patient characteristics
independently associated with coffee consumption, sleeping and smoking.
Those factors with a p value <0.05 in the univariate analyses
were selected as candidate variables for backward multivariable
logistical regressions. Finally, focused analysis of coffee consumption,
sleeping and smoking association with CAP and LSM was performed in
unadjusted and three adjusted models (Model 1, 2 and 3) to determine the
consistency or change of influence among variables. All the statistical
analyses were performed using SPSS V.22.0 (SPSS Inc, Chicago, Illinois,
USA). Statistical tests were two-tailed and significance was set at
0.05.