Data analysis
The data are input into the computer by a dedicated person. After all studies are completed, unblinding and subsequent statistical processing will be carried out according to standard procedures. The data with homogeneous variances will be expressed as mean ± standard deviation, and the data with heterogeneous variances will be expressed as median (interquartile spread). The chi-squared test will be used for count data, and the t-test will be used for measurement data. All participants who remained eligible at their initial brochure mailing date will be analyzed according to the group they were originally assigned. Missing data will be closely tracked.