Non-response is a serious threat to the external validity of longitudinal psychosocial studies. Little is known about potential systematic differences between patients with coronary artery disease who complete a psychosocial study and those who drop out prematurely due to non-response, or whether drop-outs may have a different cardiovascular risk. We studied a cohort of 1132 consecutive patients undergoing percutaneous coronary intervention (PCI). At baseline, all patients completed the Hospital Anxiety and Depression Scale (HADS) and the Type D Scale (DS14). At 12 months follow-up, 70.8% (n-=-802) of patients completed both questionnaires, while 29.2% (n-=-330) dropped out. We observed significant differences in socio-demographic, clinical, and psychological baseline characteristics between completers and drop-outs. Drop-outs were younger, more likely to smoke, but less often prescribed cardiovascular medications, including calcium antagonists and angiotensin-converting enzyme inhibitors, as compared with completers. Drop-outs more often had depression, anxiety, and negative affectivity, as compared with completers (all p-values <0.05). After a median follow-up of 4 years, we found no significant differences in mortality risk between completers and drop-outs (6.5 vs. 7.3%; adjusted HR 1.34, 95% CI 0.82-2.19, respectively). In conclusion, a possible attrition bias occurred, as drop-outs and completers differed systematically on some socio-demographic, clinical, and psychological baseline characteristics. Despite these differences, this did not translate into a poorer short-term prognosis, as there were no differences in the mortality risk of completers vs. drop-outs after a median follow-up of 4 years. In future prospective studies, attention should be paid to attrition bias, and its possible impact on study results and implications should be discussed.

Additional Metadata
Keywords Anxiety, baseline characteristics, depression, drop-outs, mortality, Type D personality
Persistent URL dx.doi.org/10.1177/2047487313506548, hdl.handle.net/1765/84269
Journal European Journal of Preventive Cardiology
Citation
Damen, N.L, Versteeg, H, Serruys, P.W.J.C, van Geuns, R.J.M, van Domburg, R.T, Pedersen, S.S, & Boersma, H. (2015). Cardiac patients who completed a longitudinal psychosocial study had a different clinical and psychosocial baseline profile than patients who dropped out prematurely. European Journal of Preventive Cardiology, 22(2), 196–199. doi:10.1177/2047487313506548