title: [Descriptive analysis of trend of epidemiological observational data using JoinPoint: a user-friendly tool, seemingly].
abstract: BACKGROUND
  Analysis of the temporal trend of epidemiological data is becoming increasingly popular. For the purpose, the JoinPoint is a widely used software. We present important elements involved when using some of the options of this software.
  
  
  METHODS
  In order to identify potential breakpoints in the trends and estimate average rates of change, JoinPoint applies piecewise regression to model the expectation of a variable that fluctuates over time.
  
  
  RESULTS
  Using breast cancer incidence data from Isère, an administrative district in France, during the period 1979-2007, we show the effects of user choices concerning the potential number of breakpoints, the research method used by the final model, the length of the period, and the weighting coefficients.
  
  
  CONCLUSIONS
  JoinPoint is useful to describe changing trends. Nevertheless, user choices have an impact on output and must be clearly identified. Moreover, the JoinPoint approach cannot replace other possible approaches for temporal analysis of observational data.
authors.affiliation: Registre du cancer de l'Isère, CHU de Grenoble, Grenoble, France. mcolonna.registre@wanadoo.fr
authors.forename: M
authors.initials: M
authors.lastname: Colonna
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology* / Q000401:mortality; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008432:Mathematical Computing; D016347:Medical Records Systems, Computerized / Q000639:trends; D012044:Regression Analysis; D012189:Retrospective Studies; D012985:Software Design; D014584:User-Computer Interface; D014798:Vital Statistics