title: Longitudinal research and data collection in primary care.
abstract: OBJECTIVE
  This article reviews examples of and experience with longitudinal research in family medicine. The objective is to use this empirical information to formulate recommendations for improving longitudinal research.
  
  
  METHODS
  The article discusses 3 longitudinal studies from the Nijmegen academic family practice research network: 1 on the prognosis of depression and 1 each on the prognosis of and outcomes of care for type 2 diabetes mellitus. The Nijmegen network has recorded all episodes of morbidity encountered in Dutch family medicine since 1971 in a stable practice population. This network's experience is evaluated to identify lessons that may help other practice-based research networks (PBRNs) in pursuing longitudinal research.
  
  
  RESULTS
  In terms of external conditions (conditions related to the general setting), the stability of a population and a high level of continuity of care substantially enhance the ability to perform longitudinal research. In terms of internal conditions (conditions related to the PBRN), motivation of family physicians and their staff to conduct ongoing data collection, and their ownership of the data are key for success. Other critical internal conditions include standardization of data; collection of data by clinician-friendly means; training of family physicians and their staff in data collection, as well as meetings for discussion of this task; provision of feedback to practices on the research findings; use of standard procedures to promote adherence to data collection; availability of facilities for regular measurement of patients' health status or chart review; and use of mechanisms for tracking patients who leave the practice area.
  
  
  CONCLUSIONS
  Insight from existing experience suggests that longitudinal research can be enhanced in PBRNs. The best way forward is to build longitudinal data collection by drawing on lessons from successful studies. Primary care research policy should advocate for a role of longitudinal research and stimulate its development in PBRNs under favorable population circumstances.
authors.affiliation: Department of Family Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands. C.vanWeel@hag.umcn.nl
authors.forename: Chris
authors.initials: C
authors.lastname: van Weel
mesh_terms: D035843:Biomedical Research / Q000379:methods*; D003625:Data Collection / Q000379:methods*; D003863:Depression / Q000628:therapy; D003920:Diabetes Mellitus / Q000628:therapy; D005194:Family Practice / Q000592:standards*; D017408:Guidelines as Topic; D006302:Health Services Research / Q000379:methods*; D006801:Humans; D008137:Longitudinal Studies; D009426:Netherlands; D011320:Primary Health Care / Q000592:standards*