Risk factors of self-reported adverse drug events among Medicare enrollees before and after Medicare Part D

OBJECTIVES: Quantify risk factors for self-reported adverse drug events (ADEs) after the implementation of Medicare Part D, quantify self-reported ADEs before and after Medicare Part D and quantify the association between self-reported ADEs and increased use of prescription medication. METHODS: The design was a longitudinal study including an internet survey before Medicare Part D in 2005 (n=1220) and a follow-up survey in 2007 (n=1024), with n=436 responding to both surveys. Harris Interactive® invited individuals in their online panel to participate in this study. Individuals who were 65 or older, English speakers, US residents and enrolled in Medicare were included. Data collected and used in analysis included self-reported ADE, socio-demographics, self-rated health, number of medications, symptoms experienced, concern and necessity beliefs about medicines, number of pharmacies, and whether doses were skipped or stopped to save money. RESULTS: In 2007, reporting an ADE was related to concern beliefs, symptoms experienced and age. ADEs were experienced by 18% of respondents in 2005 and 20.4% in 2007. The average number of medications increased from 3.82 (SD=2.82) in 2005 to 4.32 (SD=3.20) in 2007 (t= -5.77, p<0.001). Among respondents who answered both surveys (n=436), 18.4% reported an ADE in 2005 while 24.3% reported an ADE in 2007. The increase in self-reported ADE was related to concern beliefs (OR=1.12, 95%CI=1.05, 1.19) and symptoms experienced (OR= 3.27, 95%CI=1.60, 6.69), not number of medications (OR=1.04, 95%CI=0.77, 1.41). CONCLUSION: Discussing elderly patients’ beliefs about their medicines may affect their medication expectations, symptom interpretation and attributions and future medication attributions.