The scope for biased recall of risk-factor exposure in case-control studies: evidence from a cohort study of Scottish men.
OBJECTIVE
Case-control studies are prone to recall bias, a participant's case-control status influencing their recall of exposure to risk factors. We aimed to demonstrate empirically the scope for this bias.


METHODS
Two thousand five hundred and fifty men without coronary heart disease at enrollment to a prospective cohort study underwent two health assessments, about 5 years apart. The association between the development of coronary heart disease in the intervening period and changes in reported stress and cigarette smoking were investigated.


RESULTS
Men admitted to hospital with coronary heart disease reported a greater increase in psychological stress (p=0.032) and greater cessation of smoking (22% vs. 10%; p=0.007) than men not admitted. Consequently, when exposure data are collected at the end rather than at the start of the follow-up period, coronary heart disease is observed to be more strongly associated with psychological stress, and more weakly associated with smoking.


CONCLUSIONS
At the time when a case-control study is conducted, levels of exposure to risk factors will have been influenced by disease development. When participants are asked about their level of exposure for a previous time period, recall is likely to be influenced by present outcome and exposure status, especially when psychological states are being investigated.
Department of Social Medicine, University of Bristol, Bristol, UK. chris.metcalfe@bristol.ac.uk
Chris
C
Metcalfe
John
J
Macleod
George Davey
GD
Smith
Carole L
CL
Hart
D000328:Adult; D015982:Bias; D016022:Case-Control Studies; D015331:Cohort Studies; D003327:Coronary Disease / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology; D012907:Smoking / Q000009:adverse effects; D016540:Smoking Cessation; D013315:Stress, Psychological / Q000150:complications; D011795:Surveys and Questionnaires