![[Visit Client Website]](/img/acr/banner_2009.gif)
Search
Print Page
Browse by Day: 
Purpose: The relationship between medication adherence and various outcomes including fracture is of substantial interest, particularly in the osteoporosis community. The extent to which adherence to medications as a behavior is a proxy for other healthy behaviors that affect outcomes is unclear. To better understand the magnitude of the effect of adherence as a behavior, we examined the relationship between adherence to placebo in the hormone therapy (HT) arm of the Women's Health Initiative (WHI) on the risk of fracture, cardiovascular events, malignancy and death.
Method: We used data from those randomized to placebo in the HT arm of the WHI. Adherence was represented as time-varying based upon pill counts and quantified as a medication possession ratio (MPR). Outcome events were identified and validated using medical records as per the original WHI protocol. Confounders were selected a-priori and based upon the ability to adjust the main exposure-outcome relationship by > 10%. Cox proportional hazards models were used to evaluate the relationship between adherence (≤ 50%, 50-80%, ≥ 80%) and each of the various outcomes, with low adherence as referent. Analyses were censored at the first event specific to each outcome.
Results: A total of 13485 women were randomized to placebo in the HT arm of the WHI and were under observation for 86091 person-years (without respect to censoring). The median (IQR) cumulative adherence to placebo at the end of the trial was 91.3% (81.4, 96.0%). There was a consistent relationship between adherence to placebo and a protective effect of all outcomes that was strongest for death and hip fracture, although not all results were statistically significant (see table). Results were not substantially affected by multivariable adjusted for various confounders.
Conclusion: Medication adherence appears to be a proxy for other unmeasured behaviors and health habits that have important effects on numerous outcomes. The magnitude of this effect was greatest for hip fracture and death. Results of future studies evaluating outcomes related to adherence to specific medications should be interpreted cautiously in light of these results.
