title: Internet-based control recruitment for a case-control study of major risk factors for stroke in Korea: lessons from the experience.
abstract: BACKGROUND
  This study aimed to estimate the population-attributable risks (PARs) of 9 major risk factors for stroke in Korea through a case-control study and to test the feasibility and validity of internet-based control recruitment.
  
  
  METHODS
  From April 2008 to September 2009, controls were enrolled via internet after providing consent for participation through a web-based survey. The cases included patients who were admitted to the participating centers due to acute stroke or transient ischemic attack within 7 days of onset during the study period. Each control was age- and sex-matched with 2 cases. Adjusted odd ratios, age-standardized prevalence, and PARs were estimated for the 9 major risk factors using the prevalence of risk factors in the control group and the age and sex characteristics from Korea's national census data.
  
  
  RESULTS
  In total, 1041 controls were matched to 2082 stroke cases. Because of a shortage of elderly controls in the internet-based recruitment, 248 controls were recruited off-line. The PARs were 23.44%, 10.95%, 51.32%, and 6.35% for hypertension, diabetes, smoking, and stroke history, respectively. Hypercholesterolemia, atrial fibrillation, obesity, coronary heart disease, and a family history of stroke were not associated with stroke. Comparison with education and religion of the control group with that mentioned in the national census data showed a notable difference.
  
  
  CONCLUSIONS
  The study results imply that internet-based control recruitment for a case-control study requires careful selection of risk factors with high self-awareness and effective strategies to facilitate the recruitment of elderly participants.
authors.affiliation: Department of Neurology, Eulji General Hospital, Eulji University, Seoul, Korea.
authors.forename: Jong-Moo
authors.initials: JM
authors.lastname: Park
authors.affiliation: Department of Neurology, Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea.
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Cho
authors.affiliation: Department of Neurology, Soonchunhyang University College of Medicine, Seoul, Korea.
authors.forename: Kyung Bok
authors.initials: KB
authors.lastname: Lee
authors.affiliation: Department of Neurology, Seoul Medical Center, Seoul, Korea.
authors.forename: Tai Hwan
authors.initials: TH
authors.lastname: Park
authors.affiliation: Department of Neurology, Eulji University Hospital, Eulji University, Daejeon, Korea.
authors.forename: Soo Joo
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: Department of Neurology, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Moon-Ku
authors.initials: MK
authors.lastname: Han
authors.affiliation: Department of Neurology, Eulji University Hospital, Eulji University, Daejeon, Korea.
authors.forename: Youngchai
authors.initials: Y
authors.lastname: Ko
authors.affiliation: Department of Neurology, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Neurology, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Jae-Kwan
authors.initials: JK
authors.lastname: Cha
authors.affiliation: Department of Neurology, Hallym University College of Medicine, Pyeongchon, Korea.
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Lee
authors.affiliation: Department of Neurology, Hallym University College of Medicine, Pyeongchon, Korea.
authors.forename: Kyung-Ho
authors.initials: KH
authors.lastname: Yu
authors.affiliation: Department of Neurology, Hallym University College of Medicine, Pyeongchon, Korea.
authors.forename: Mi-Sun
authors.initials: MS
authors.lastname: Oh
authors.affiliation: Biostatistical Consulting Unit, Soonchunhyang University Medical Center, Seoul, Korea.
authors.forename: Ji Sung
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Biostatistics, Korea University College of Medicine, Seoul, Korea.
authors.forename: Juneyoung
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Neurology, Seoul National University Bundang Hospital, Seongnam, Korea. Electronic address: braindoc@snu.ac.kr.
authors.forename: Hee-Joon
authors.initials: HJ
authors.lastname: Bae
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003920:Diabetes Mellitus / Q000453:epidemiology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000453:epidemiology; D020407:Internet; D002546:Ischemic Attack, Transient / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D015995:Prevalence; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology; D020521:Stroke / Q000453:epidemiology / Q000209:etiology*
keywords: Case-control study; internet-based study; risk factors; stroke