Aim: The objectives of the present study were to test Spilker's quality of life model in the elderly population consuming over-the-counter (OTC) medications. It was hypothesized that OTC medication misuse increases adverse drug events (ADEs), ADEs as a result of OTC medication misuse decrease health-related quality of life (HRQoL) and the impact of OTC medication misuse on patients' HRQoL is fully medicated by ADEs associated with OTC medications.
Methods: Data were used from a previously carried out cross-sectional study using survey instruments with elderly patients consuming OTC medications in Houston, Texas, USA. The presence/absence of OTC misuse was assessed by an expert panel based on patient reported information on drug use characteristics; ADE was self-reported and HRQoL was measured using the Short Form-12v2, which contains a physical component summary score (PCS) and a mental component summary score (MCS).
Results: Of the 154 respondents, 18.2% misused OTC medications and 22.1% reported ADE as a result of OTC medications. The mean ± SD score of PCS and MCS was 40.6 ± 6.8 and 46.4 ± 7, respectively. The hypothesized framework provided a well-fitted solution to the data (χ(2) = 1.387, d.f. = 2, P = 0.49; weighted root mean square residual = 0.317). Misuse of OTC medications significantly increased ADEs associated with OTC medications (β = 0.298) and increased ADEs significantly decreased patient reported PCS (β = -0.312), but not MCS (β = -0.213). OTC medication misuse indirectly decreased PCS and MCS by mediating the effect of an increase in ADE; however, the association was not statistically significant.
Conclusions: Misuse of OTC medications is highly associated with ADEs. ADEs are capable of decreasing the physical health of elderly patients.
Keywords: Short Form-12; adverse drug event; misuse; over-the-counter drugs; quality of life.
© 2015 Japan Geriatrics Society.