Adherence to Lipid-lowering Therapy and the Use of Preventive Health Services: An Investigation of the Healthy User Effect

Abstract

Patients who adhere to preventive therapies may be more likely to engage in a broad spectrum of behaviors consistent with a healthy lifestyle. Because many of these behaviors cannot be measured easily, observational studies of outcomes associated with the long-term use of preventive therapies are subject to the so-called "healthy user bias." To better understand this effect, the authors examined the association between adherence to statin therapy and the use of preventive health services in a Pennsylvania cohort of 20,783 new users of statins between 1996 and 2004. After adjustment for age, gender, and various comorbid conditions, patients who filled two or more prescriptions for a statin during a 1-year ascertainment period were more likely than patients who filled only one prescription to receive prostate-specific antigen tests (hazard ratio (HR)=1.57, 95% confidence interval (CI): 1.17, 2.19), fecal occult blood tests (HR=1.31, 95% CI: 1.12, 1.53), screening mammograms (HR=1.22, 95% CI: 1.09, 1.38), influenza vaccinations (HR=1.21, 95% CI: 1.12, 1.31), and pneumococcal vaccinations (HR=1.46, 95% CI: 1.17, 1.83) during follow-up. These results suggest that patients who adhere to chronic therapies are more likely to seek out preventive health services, such as screening tests and vaccinations. Further work is needed to identify study design and analysis methods that can be used to minimize the healthy user bias in studies of preventive therapies.

Trajectories of Diabetes Medication Adherence and Hospitalization Risk: A Retrospective Cohort Study in a Large State Medicaid Program

“…We also included the number of anti-diabetes medication classes, insulin use, and having diabetes-related tests in the 12 months after the index oral hypoglycemic prescription ED emergency department, HR hazard ratio, PDC proportion of days covered out unmeasured confounders (e.g., healthy user bias) in this observational study. 58 However, including variables for receiving recommended screenings (proxy measures of healthy behavior) did not impact the results. Finally, we cannot rule out the possibility that our sample includes pre-diabetes patients receiving metformin alone or patients who had been non-adherers and were reinitiating treatment.…”

Leisure-time physical activity, cardiovascular risk factors and mortality during a 34-year follow-up in men

“…In other words, people who initiate and adhere to preventive habits may be systemically healthier and more health-seeking than others. [3] Furthermore, the physical activity of work and leisure time, lifestyle and other stress factors differ in both their prevalence and modifiability in various socioeconomic groups, and consequently, population-based studies may not reflect the effects of physical activity as such. In order to reduce some of these caveats, we studied the associations between leisure-time physical activity and 34-year mortality in an initially healthy and socioeconomically homogeneous cohort of middle-aged men in Helsinki, Finland.…”

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.…”