Indications of recall bias found in a retrospective study of physical activity and myocardial infarction

ObjectiveTo evaluate the presence of recall bias in retrospective studies of physical activity and myocardial infarction.Study Design and SettingIn 2005, seventy-eight cases who had suffered from a myocardial infarction and 243 control subjects, who had previously participated in the Swedish WOLF (Work, Lipids, and Fibrinogen) study, were asked about their physical activity level during 1990–2005. The answers about recalled past leisure time, occupational, and household physical activity level were compared with physical activity level as reported at the baseline examination of the WOLF study in 1992–1998.ResultsThe proportion who recalled the same activity level as originally reported ranged from 69% to 96% (cases) and 69% to 89% (controls), and the kappa values ranged from 0.30 to 0.91 (cases) and 0.46 to 0.59 (controls), with the exception of perceived physical workload in household work, which showed low agreement between the originally stated and later recalled activity levels. Some differences were found between cases and controls regarding recall of past occupational activity, indicating the presence of recall bias in this domain of physical activity.ConclusionWe cannot preclude the existence of recall bias when using retrospectively recalled information about occupational physical activity in studies of physical activity and myocardial infarction.