Statin Adherence and Risk of Accidents

Abstract

Background-Bias in studies of preventive medications can occur when healthier patients are more likely to initiate and adhere to therapy than less healthy patients. We sought evidence of this bias by examining associations between statin exposure and various outcomes that should not be causally affected by statin exposure, such as workplace and motor vehicle accidents. Methods and Results-We conducted a prospective cohort study of statin patients using data from British Columbia, Canada, a multiethnic society with a population of 4.3 million people. Study subjects were 141 086 patients who initiated statins for primary prevention. We examined the association between adherence and multiple outcomes such as accidents and screening procedures using multivariable-adjusted Cox proportional hazards models. The study population was 49% female and had an average age of 61 years. The results from our multivariable-adjusted models showed that more adherent patients were less likely to have accidents than less adherent patients. This effect was greatest for motor vehicle accidents (hazard ratio, 0.75; 95% confidence interval, 0.72 to 0.79) and workplace accidents (hazard ratio, 0.77; 95% confidence interval, 0.74 to 0.81). More adherent patients had a greater likelihood of using screening services (hazard ratio, 1.17; 95% confidence interval, 1.15 to 1.20) and a lower likelihood of developing other diseases likely to be unrelated to a biological affect of a statin (hazard ratio, 0.87; 95% confidence interval, 0.86 to 0.89). Conclusions-Our study contributes compelling evidence that patients who adhere to statins are systematically more health seeking than comparable patients who do not remain adherent. Caution is warranted when interpreting analyses that attribute surprising protective effects to preventive medications.

Frequency of Development of Connective Tissue Disease in Statin-Users Versus Nonusers

“…22 Observational studies often include heterogeneous patient populations with differences in baseline characteristics between treatment and control groups. Statin users ultimately have higher disease burden necessitating a statin prescription; hence, they may have a higher risk of developing diseases that may be unrelated to statin exposure.…”

“…In a large prospective cohort study, statin-adherent patients were less likely than nonadherent patients to have motor vehicle accidents and workplace accidents, after adjusting for potential confounders. 22 Additionally, statin use may act as a surrogate marker for better access to care, because adherence to statin therapy was associated with the use of preventive health services. 23 Propensity score matching helps to alleviate some of the limitations of observational studies.…”

Observational Research Using Propensity Scores

“…that confounding (and the risk for worse outcomes) may not be fully controllable. [18][19][20] Distributions and plots of PS values reflect this lack of exchangeability 21 with a high likelihood of residual confounding. PS matching would result in identification of only a small minority, while weighting may exaggerate treatment effects among atypical users.…”

Healthy users, healthy adherers, and healthy behaviors?

“…Are patients who take osteoporosis medications like patients who adhere to statins in that they may take fewer risks and have fewer accidents? (9) If this is so, we also would expect fewer nonvertebral nonhip fractures in the good adherers.…”

“…For example, patients who adhere to statins more frequently receive vaccinations and screening services. (7) These same patients also may have less comorbidity and better functional status, (8) increasing the likelihood of other healthy behaviors These patients also may be involved in fewer accidents, (9) suggesting possible risk aversion. A second potential bias-the healthy adherer bias-was first demonstrated in 1980 when decreased mortality and fewer cardiovascular events were found in good adherers of placebo in a randomized clinical trial of a cardiovascular agent.…”