Adherence to pharmacotherapy in the elderly

Abstract

Adherence is defined as accordance between prescribed therapy and patient behavior (Haynes 1979). This term covers not only pharmacotherapy but also other health-related advice from professional health workers. Despite the prominent significance of adherence for treatment, prevention, and rehabilitation success, rather little scientific work is done on this topic. This may be due in part to methodological problems such as how exactly to measure adherence. Second, although different categories of nonadherence are defined, their delineation seems to be rather arbitrary (e.g., intended vs. unintended nonadherence). Therefore, prevalence data of nonadherence are difficult to obtain even in well-controlled scientific studies (e.g., randomized controlled trials [RCTs]) (Kruse 1995; Spilker 1991). This explains why conflicting data concerning nonadherence exist in the literature, with prevalence rates for nonadherence ranging from 15% to 93%. For example, nonadherence to prescribed medications may be reported to be as high as 50% in arterial hypertension; in general, it will be higher in asymptomatic (such as arterial hypertension) than symptomatic diseases. Despite these large ranges concerning prevalence data, there is evidence for a consistently increasing rate of nonadherence with increasing number of drugs prescribed (Spagnoli et al. 1989). Simultaneous prescription of five and more drugs is considered critical in this context (McElnay and McCallion 1998).