To reduce the likelihood of reporting spurious changes in trends, we used a maximum of two joinpoints (i.e., up to three different trends), with a minimum of 8 years between joinpoints.
All statistical analyses were conducted in Stata version 12. Average annual percentage changes (AAPC) in five-year survival between 1992 and 2006 were calculated using the 'Joinpoint' software [15] with an overall significance level of alpha = 0.05, and a maximum of two joinpoints [16].
The analyses in this study started with the minimum number of joinpoints and tested for model fit with a maximum of four joinpoints.
We allowed a maximum of three joinpoints for estimations.
14 15 For our analysis, a minimum of 4 weeks between two joinpoints were required, and a maximum of three joinpoints were allowed for describing the data.
We assigned the birth‐year as an independent variable and the prevalence of H. pylori infection and the proportion of high‐risk individuals for gastric cancer as dependent variables while setting a maximum of five joinpoints.
A maximum of three joinpoints was allowed for estimations.
A maximum of three joinpoints were allowed for the number of years included in the analysis.
A maximum of three joinpoints and four line segments were allowed for each model.
Based on the Joinpoint Regression Program's recommendations for the number of time points of observations in our study, our analyses allowed a maximum of five joinpoints meaning that between one and six trend segments could be in the final model depending on the number of joinpoints detected.
