To the Editor We thank Dhamoon et al1 for their prospective longitudinal cohort study assessing the long-term disability trajectory before and after an ischemic stroke compared with myocardial infarction (MI). The authors found that the gradient of increasing disability was significantly steeper after a stroke but remained consistent after MI.
However, we noticed that many of the covariates that were assessed, including demographic and lifestyle variables, were self-reported by the participants. Self-reporting is subject to systematic errors and bias and therefore influences results. Studies show that social desirability traits are often associated with an overreporting of physical activity and underreporting of energy intake.2 It is widely accepted that physical activity is an important factor in disability; therefore, having self-reported values of physical activity introduces reporting bias and questions the validity of the study. Such bias could be reduced through using appropriate survey and questionnaire designs.